Message-ID: <d9020d20-f512-42e6-8259-a7377c3d0d58@suse.de>
Date:   Thu, 28 Sep 2023 15:59:01 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH/RFC 3/3] drm: Split drm_modeset_helper_vtables.h

Hi Geert

Am 28.09.23 um 14:16 schrieb Geert Uytterhoeven:
> <drm/drm_modeset_helper_vtables.h> is the second largest header file in
> the DRM subsystem, and declares helpers vtables for various DRM
> components.  Several vtables contain methods with the same name, and all
> but one vtable do not fit on the screen, making it hard to navigate to
> the actual method one is interested in.
> 
> Make it easier for the casual reviewer to keep track by splitting
> <drm/drm_modeset_helper_vtables.h> in multiple header files, one per DRM
> component.

I never liked this header either, but do we need new header files? Each 
struct could be appended to the end of the regular header: struct 
drm_plane_helper_funcs to drm_plane.h, drm_connector_helper_func to 
drm_connector.h and so on.

Best regards
Thomas

> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> RFC, a future patch could replace inclusion of
> <drm/drm_modeset_helper_vtables.h> by inclusion of one or more of the
> new files, and reduce compilation time.
> ---
>   include/drm/drm_connector_helper_vtable.h   |  364 +++++
>   include/drm/drm_crtc_helper_vtable.h        |  483 ++++++
>   include/drm/drm_encoder_helper_vtable.h     |  381 +++++
>   include/drm/drm_mode_config_helper_vtable.h |   97 ++
>   include/drm/drm_modeset_helper_vtables.h    | 1466 +------------------
>   include/drm/drm_plane_helper_vtable.h       |  297 ++++
>   6 files changed, 1627 insertions(+), 1461 deletions(-)
>   create mode 100644 include/drm/drm_connector_helper_vtable.h
>   create mode 100644 include/drm/drm_crtc_helper_vtable.h
>   create mode 100644 include/drm/drm_encoder_helper_vtable.h
>   create mode 100644 include/drm/drm_mode_config_helper_vtable.h
>   create mode 100644 include/drm/drm_plane_helper_vtable.h
> 
> diff --git a/include/drm/drm_connector_helper_vtable.h b/include/drm/drm_connector_helper_vtable.h
> new file mode 100644
> index 0000000000000000..92db9784e4e37e02
> --- /dev/null
> +++ b/include/drm/drm_connector_helper_vtable.h
> @@ -0,0 +1,364 @@
> +/*
> + * Copyright © 2006 Keith Packard
> + * Copyright © 2007-2008 Dave Airlie
> + * Copyright © 2007-2008 Intel Corporation
> + *   Jesse Barnes <jesse.barnes@...el.com>
> + * Copyright © 2011-2013 Intel Corporation
> + * Copyright © 2015 Intel Corporation
> + *   Daniel Vetter <daniel.vetter@...ll.ch>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __DRM_CONNECTOR_HELPER_VTABLE_H__
> +#define __DRM_CONNECTOR_HELPER_VTABLE_H__
> +
> +struct drm_writeback_connector;
> +struct drm_writeback_job;
> +
> +/**
> + * struct drm_connector_helper_funcs - helper operations for connectors
> + *
> + * These functions are used by the atomic and legacy modeset helpers and by the
> + * probe helpers.
> + */
> +struct drm_connector_helper_funcs {
> +	/**
> +	 * @get_modes:
> +	 *
> +	 * This function should fill in all modes currently valid for the sink
> +	 * into the &drm_connector.probed_modes list. It should also update the
> +	 * EDID property by calling drm_connector_update_edid_property().
> +	 *
> +	 * The usual way to implement this is to cache the EDID retrieved in the
> +	 * probe callback somewhere in the driver-private connector structure.
> +	 * In this function drivers then parse the modes in the EDID and add
> +	 * them by calling drm_add_edid_modes(). But connectors that drive a
> +	 * fixed panel can also manually add specific modes using
> +	 * drm_mode_probed_add(). Drivers which manually add modes should also
> +	 * make sure that the &drm_connector.display_info,
> +	 * &drm_connector.width_mm and &drm_connector.height_mm fields are
> +	 * filled in.
> +	 *
> +	 * Note that the caller function will automatically add standard VESA
> +	 * DMT modes up to 1024x768 if the .get_modes() helper operation returns
> +	 * no mode and if the connector status is connector_status_connected or
> +	 * connector_status_unknown. There is no need to call
> +	 * drm_add_modes_noedid() manually in that case.
> +	 *
> +	 * Virtual drivers that just want some standard VESA mode with a given
> +	 * resolution can call drm_add_modes_noedid(), and mark the preferred
> +	 * one using drm_set_preferred_mode().
> +	 *
> +	 * This function is only called after the @detect hook has indicated
> +	 * that a sink is connected and when the EDID isn't overridden through
> +	 * sysfs or the kernel commandline.
> +	 *
> +	 * This callback is used by the probe helpers in e.g.
> +	 * drm_helper_probe_single_connector_modes().
> +	 *
> +	 * To avoid races with concurrent connector state updates, the helper
> +	 * libraries always call this with the &drm_mode_config.connection_mutex
> +	 * held. Because of this it's safe to inspect &drm_connector->state.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * The number of modes added by calling drm_mode_probed_add().
> +	 */
> +	int (*get_modes)(struct drm_connector *connector);
> +
> +	/**
> +	 * @detect_ctx:
> +	 *
> +	 * Check to see if anything is attached to the connector. The parameter
> +	 * force is set to false whilst polling, true when checking the
> +	 * connector due to a user request. force can be used by the driver to
> +	 * avoid expensive, destructive operations during automated probing.
> +	 *
> +	 * This callback is optional, if not implemented the connector will be
> +	 * considered as always being attached.
> +	 *
> +	 * This is the atomic version of &drm_connector_funcs.detect.
> +	 *
> +	 * To avoid races against concurrent connector state updates, the
> +	 * helper libraries always call this with ctx set to a valid context,
> +	 * and &drm_mode_config.connection_mutex will always be locked with
> +	 * the ctx parameter set to this ctx. This allows taking additional
> +	 * locks as required.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * &drm_connector_status indicating the connector's status,
> +	 * or the error code returned by drm_modeset_lock(), -EDEADLK.
> +	 */
> +	int (*detect_ctx)(struct drm_connector *connector,
> +			  struct drm_modeset_acquire_ctx *ctx,
> +			  bool force);
> +
> +	/**
> +	 * @mode_valid:
> +	 *
> +	 * Callback to validate a mode for a connector, irrespective of the
> +	 * specific display configuration.
> +	 *
> +	 * This callback is used by the probe helpers to filter the mode list
> +	 * (which is usually derived from the EDID data block from the sink).
> +	 * See e.g. drm_helper_probe_single_connector_modes().
> +	 *
> +	 * This function is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This only filters the mode list supplied to userspace in the
> +	 * GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid,
> +	 * &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid,
> +	 * which are also called by the atomic helpers from
> +	 * drm_atomic_helper_check_modeset(). This allows userspace to force and
> +	 * ignore sink constraint (like the pixel clock limits in the screen's
> +	 * EDID), which is useful for e.g. testing, or working around a broken
> +	 * EDID. Any source hardware constraint (which always need to be
> +	 * enforced) therefore should be checked in one of the above callbacks,
> +	 * and not this one here.
> +	 *
> +	 * To avoid races with concurrent connector state updates, the helper
> +	 * libraries always call this with the &drm_mode_config.connection_mutex
> +	 * held. Because of this it's safe to inspect &drm_connector->state.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum
> +	 * drm_mode_status.
> +	 */
> +	enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
> +					   struct drm_display_mode *mode);
> +
> +	/**
> +	 * @mode_valid_ctx:
> +	 *
> +	 * Callback to validate a mode for a connector, irrespective of the
> +	 * specific display configuration.
> +	 *
> +	 * This callback is used by the probe helpers to filter the mode list
> +	 * (which is usually derived from the EDID data block from the sink).
> +	 * See e.g. drm_helper_probe_single_connector_modes().
> +	 *
> +	 * This function is optional, and is the atomic version of
> +	 * &drm_connector_helper_funcs.mode_valid.
> +	 *
> +	 * To allow for accessing the atomic state of modesetting objects, the
> +	 * helper libraries always call this with ctx set to a valid context,
> +	 * and &drm_mode_config.connection_mutex will always be locked with
> +	 * the ctx parameter set to @ctx. This allows for taking additional
> +	 * locks as required.
> +	 *
> +	 * Even though additional locks may be acquired, this callback is
> +	 * still expected not to take any constraints into account which would
> +	 * be influenced by the currently set display state - such constraints
> +	 * should be handled in the driver's atomic check. For example, if a
> +	 * connector shares display bandwidth with other connectors then it
> +	 * would be ok to validate the minimum bandwidth requirement of a mode
> +	 * against the maximum possible bandwidth of the connector. But it
> +	 * wouldn't be ok to take the current bandwidth usage of other
> +	 * connectors into account, as this would change depending on the
> +	 * display state.
> +	 *
> +	 * Returns:
> +	 * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
> +	 * the &enum drm_mode_status value to @status, or a negative error
> +	 * code otherwise.
> +	 *
> +	 */
> +	int (*mode_valid_ctx)(struct drm_connector *connector,
> +			      struct drm_display_mode *mode,
> +			      struct drm_modeset_acquire_ctx *ctx,
> +			      enum drm_mode_status *status);
> +
> +	/**
> +	 * @best_encoder:
> +	 *
> +	 * This function should select the best encoder for the given connector.
> +	 *
> +	 * This function is used by both the atomic helpers (in the
> +	 * drm_atomic_helper_check_modeset() function) and in the legacy CRTC
> +	 * helpers.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * In atomic drivers this function is called in the check phase of an
> +	 * atomic update. The driver is not allowed to change or inspect
> +	 * anything outside of arguments passed-in. Atomic drivers which need to
> +	 * inspect dynamic configuration state should instead use
> +	 * @atomic_best_encoder.
> +	 *
> +	 * You can leave this function to NULL if the connector is only
> +	 * attached to a single encoder. In this case, the core will call
> +	 * drm_connector_get_single_encoder() for you.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * Encoder that should be used for the given connector and connector
> +	 * state, or NULL if no suitable encoder exists. Note that the helpers
> +	 * will ensure that encoders aren't used twice, drivers should not check
> +	 * for this.
> +	 */
> +	struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
> +
> +	/**
> +	 * @atomic_best_encoder:
> +	 *
> +	 * This is the atomic version of @best_encoder for atomic drivers which
> +	 * need to select the best encoder depending upon the desired
> +	 * configuration and can't select it statically.
> +	 *
> +	 * This function is used by drm_atomic_helper_check_modeset().
> +	 * If it is not implemented, the core will fallback to @best_encoder
> +	 * (or drm_connector_get_single_encoder() if @best_encoder is NULL).
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of an atomic update. The
> +	 * driver is not allowed to change anything outside of the
> +	 * &drm_atomic_state update tracking structure passed in.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * Encoder that should be used for the given connector and connector
> +	 * state, or NULL if no suitable encoder exists. Note that the helpers
> +	 * will ensure that encoders aren't used twice, drivers should not check
> +	 * for this.
> +	 */
> +	struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
> +						   struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_check:
> +	 *
> +	 * This hook is used to validate connector state. This function is
> +	 * called from &drm_atomic_helper_check_modeset, and is called when
> +	 * a connector property is set, or a modeset on the crtc is forced.
> +	 *
> +	 * Because &drm_atomic_helper_check_modeset may be called multiple times,
> +	 * this function should handle being called multiple times as well.
> +	 *
> +	 * This function is also allowed to inspect any other object's state and
> +	 * can add more state objects to the atomic commit if needed. Care must
> +	 * be taken though to ensure that state check and compute functions for
> +	 * these added states are all called, and derived state in other objects
> +	 * all updated. Again the recommendation is to just call check helpers
> +	 * until a maximal configuration is reached.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of an atomic update. The
> +	 * driver is not allowed to change anything outside of the free-standing
> +	 * state objects passed-in or assembled in the overall &drm_atomic_state
> +	 * update tracking structure.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success, -EINVAL if the state or the transition can't be
> +	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> +	 * attempt to obtain another state object ran into a &drm_modeset_lock
> +	 * deadlock.
> +	 */
> +	int (*atomic_check)(struct drm_connector *connector,
> +			    struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_commit:
> +	 *
> +	 * This hook is to be used by drivers implementing writeback connectors
> +	 * that need a point when to commit the writeback job to the hardware.
> +	 * The writeback_job to commit is available in the new connector state,
> +	 * in &drm_connector_state.writeback_job.
> +	 *
> +	 * This hook is optional.
> +	 *
> +	 * This callback is used by the atomic modeset helpers.
> +	 */
> +	void (*atomic_commit)(struct drm_connector *connector,
> +			      struct drm_atomic_state *state);
> +
> +	/**
> +	 * @prepare_writeback_job:
> +	 *
> +	 * As writeback jobs contain a framebuffer, drivers may need to
> +	 * prepare and clean them up the same way they can prepare and
> +	 * clean up framebuffers for planes. This optional connector operation
> +	 * is used to support the preparation of writeback jobs. The job
> +	 * prepare operation is called from drm_atomic_helper_prepare_planes()
> +	 * for struct &drm_writeback_connector connectors only.
> +	 *
> +	 * This operation is optional.
> +	 *
> +	 * This callback is used by the atomic modeset helpers.
> +	 */
> +	int (*prepare_writeback_job)(struct drm_writeback_connector *connector,
> +				     struct drm_writeback_job *job);
> +	/**
> +	 * @cleanup_writeback_job:
> +	 *
> +	 * This optional connector operation is used to support the
> +	 * cleanup of writeback jobs. The job cleanup operation is called
> +	 * from the existing drm_writeback_cleanup_job() function, invoked
> +	 * both when destroying the job as part of an aborted commit, or when
> +	 * the job completes.
> +	 *
> +	 * This operation is optional.
> +	 *
> +	 * This callback is used by the atomic modeset helpers.
> +	 */
> +	void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
> +				      struct drm_writeback_job *job);
> +
> +	/**
> +	 * @enable_hpd:
> +	 *
> +	 * Enable hot-plug detection for the connector.
> +	 *
> +	 * This operation is optional.
> +	 *
> +	 * This callback is used by the drm_kms_helper_poll_enable() helpers.
> +	 */
> +	void (*enable_hpd)(struct drm_connector *connector);
> +
> +	/**
> +	 * @disable_hpd:
> +	 *
> +	 * Disable hot-plug detection for the connector.
> +	 *
> +	 * This operation is optional.
> +	 *
> +	 * This callback is used by the drm_kms_helper_poll_disable() helpers.
> +	 */
> +	void (*disable_hpd)(struct drm_connector *connector);
> +};
> +
> +/**
> + * drm_connector_helper_add - sets the helper vtable for a connector
> + * @connector: DRM connector
> + * @funcs: helper vtable to set for @connector
> + */
> +static inline void drm_connector_helper_add(struct drm_connector *connector,
> +					    const struct drm_connector_helper_funcs *funcs)
> +{
> +	connector->helper_private = funcs;
> +}
> +
> +#endif /* __DRM_CONNECTOR_HELPER_VTABLE_H__ */
> diff --git a/include/drm/drm_crtc_helper_vtable.h b/include/drm/drm_crtc_helper_vtable.h
> new file mode 100644
> index 0000000000000000..6dc5d4d7af494a1b
> --- /dev/null
> +++ b/include/drm/drm_crtc_helper_vtable.h
> @@ -0,0 +1,483 @@
> +/*
> + * Copyright © 2006 Keith Packard
> + * Copyright © 2007-2008 Dave Airlie
> + * Copyright © 2007-2008 Intel Corporation
> + *   Jesse Barnes <jesse.barnes@...el.com>
> + * Copyright © 2011-2013 Intel Corporation
> + * Copyright © 2015 Intel Corporation
> + *   Daniel Vetter <daniel.vetter@...ll.ch>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __DRM_CRTC_HELPER_VTABLE_H__
> +#define __DRM_CRTC_HELPER_VTABLE_H__
> +
> +enum mode_set_atomic {
> +	LEAVE_ATOMIC_MODE_SET,
> +	ENTER_ATOMIC_MODE_SET,
> +};
> +
> +/**
> + * struct drm_crtc_helper_funcs - helper operations for CRTCs
> + *
> + * These hooks are used by the legacy CRTC helpers and the new atomic
> + * modesetting helpers.
> + */
> +struct drm_crtc_helper_funcs {
> +	/**
> +	 * @dpms:
> +	 *
> +	 * Callback to control power levels on the CRTC.  If the mode passed in
> +	 * is unsupported, the provider must use the next lowest power level.
> +	 * This is used by the legacy CRTC helpers to implement DPMS
> +	 * functionality in drm_helper_connector_dpms().
> +	 *
> +	 * This callback is also used to disable a CRTC by calling it with
> +	 * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for enabling and disabling a CRTC to
> +	 * facilitate transitions to atomic, but it is deprecated. Instead
> +	 * @atomic_enable and @atomic_disable should be used.
> +	 */
> +	void (*dpms)(struct drm_crtc *crtc, int mode);
> +
> +	/**
> +	 * @prepare:
> +	 *
> +	 * This callback should prepare the CRTC for a subsequent modeset, which
> +	 * in practice means the driver should disable the CRTC if it is
> +	 * running. Most drivers ended up implementing this by calling their
> +	 * @dpms hook with DRM_MODE_DPMS_OFF.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for disabling a CRTC to facilitate
> +	 * transitions to atomic, but it is deprecated. Instead @atomic_disable
> +	 * should be used.
> +	 */
> +	void (*prepare)(struct drm_crtc *crtc);
> +
> +	/**
> +	 * @commit:
> +	 *
> +	 * This callback should commit the new mode on the CRTC after a modeset,
> +	 * which in practice means the driver should enable the CRTC.  Most
> +	 * drivers ended up implementing this by calling their @dpms hook with
> +	 * DRM_MODE_DPMS_ON.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for enabling a CRTC to facilitate
> +	 * transitions to atomic, but it is deprecated. Instead @atomic_enable
> +	 * should be used.
> +	 */
> +	void (*commit)(struct drm_crtc *crtc);
> +
> +	/**
> +	 * @mode_valid:
> +	 *
> +	 * This callback is used to check if a specific mode is valid in this
> +	 * crtc. This should be implemented if the crtc has some sort of
> +	 * restriction in the modes it can display. For example, a given crtc
> +	 * may be responsible to set a clock value. If the clock can not
> +	 * produce all the values for the available modes then this callback
> +	 * can be used to restrict the number of modes to only the ones that
> +	 * can be displayed.
> +	 *
> +	 * This hook is used by the probe helpers to filter the mode list in
> +	 * drm_helper_probe_single_connector_modes(), and it is used by the
> +	 * atomic helpers to validate modes supplied by userspace in
> +	 * drm_atomic_helper_check_modeset().
> +	 *
> +	 * This function is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * Since this function is both called from the check phase of an atomic
> +	 * commit, and the mode validation in the probe paths it is not allowed
> +	 * to look at anything else but the passed-in mode, and validate it
> +	 * against configuration-invariant hardware constraints. Any further
> +	 * limits which depend upon the configuration can only be checked in
> +	 * @mode_fixup or @atomic_check.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * drm_mode_status Enum
> +	 */
> +	enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
> +					   const struct drm_display_mode *mode);
> +
> +	/**
> +	 * @mode_fixup:
> +	 *
> +	 * This callback is used to validate a mode. The parameter mode is the
> +	 * display mode that userspace requested, adjusted_mode is the mode the
> +	 * encoders need to be fed with. Note that this is the inverse semantics
> +	 * of the meaning for the &drm_encoder and &drm_bridge_funcs.mode_fixup
> +	 * vfunc. If the CRTC cannot support the requested conversion from mode
> +	 * to adjusted_mode it should reject the modeset. See also
> +	 * &drm_crtc_state.adjusted_mode for more details.
> +	 *
> +	 * This function is used by both legacy CRTC helpers and atomic helpers.
> +	 * With atomic helpers it is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of atomic modesets, which
> +	 * can be aborted for any reason (including on userspace's request to
> +	 * just check whether a configuration would be possible). Atomic drivers
> +	 * MUST NOT touch any persistent state (hardware or software) or data
> +	 * structures except the passed in adjusted_mode parameter.
> +	 *
> +	 * This is in contrast to the legacy CRTC helpers where this was
> +	 * allowed.
> +	 *
> +	 * Atomic drivers which need to inspect and adjust more state should
> +	 * instead use the @atomic_check callback, but note that they're not
> +	 * perfectly equivalent: @mode_valid is called from
> +	 * drm_atomic_helper_check_modeset(), but @atomic_check is called from
> +	 * drm_atomic_helper_check_planes(), because originally it was meant for
> +	 * plane update checks only.
> +	 *
> +	 * Also beware that userspace can request its own custom modes, neither
> +	 * core nor helpers filter modes to the list of probe modes reported by
> +	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> +	 * that modes are filtered consistently put any CRTC constraints and
> +	 * limits checks into @mode_valid.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * True if an acceptable configuration is possible, false if the modeset
> +	 * operation should be rejected.
> +	 */
> +	bool (*mode_fixup)(struct drm_crtc *crtc,
> +			   const struct drm_display_mode *mode,
> +			   struct drm_display_mode *adjusted_mode);
> +
> +	/**
> +	 * @mode_set:
> +	 *
> +	 * This callback is used by the legacy CRTC helpers to set a new mode,
> +	 * position and framebuffer. Since it ties the primary plane to every
> +	 * mode change it is incompatible with universal plane support. And
> +	 * since it can't update other planes it's incompatible with atomic
> +	 * modeset support.
> +	 *
> +	 * This callback is only used by CRTC helpers and deprecated.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success or a negative error code on failure.
> +	 */
> +	int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
> +			struct drm_display_mode *adjusted_mode, int x, int y,
> +			struct drm_framebuffer *old_fb);
> +
> +	/**
> +	 * @mode_set_nofb:
> +	 *
> +	 * This callback is used to update the display mode of a CRTC without
> +	 * changing anything of the primary plane configuration. This fits the
> +	 * requirement of atomic and hence is used by the atomic helpers.
> +	 *
> +	 * Note that the display pipe is completely off when this function is
> +	 * called. Atomic drivers which need hardware to be running before they
> +	 * program the new display mode (e.g. because they implement runtime PM)
> +	 * should not use this hook. This is because the helper library calls
> +	 * this hook only once per mode change and not every time the display
> +	 * pipeline is suspended using either DPMS or the new "ACTIVE" property.
> +	 * Which means register values set in this callback might get reset when
> +	 * the CRTC is suspended, but not restored.  Such drivers should instead
> +	 * move all their CRTC setup into the @atomic_enable callback.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*mode_set_nofb)(struct drm_crtc *crtc);
> +
> +	/**
> +	 * @mode_set_base:
> +	 *
> +	 * This callback is used by the legacy CRTC helpers to set a new
> +	 * framebuffer and scanout position. It is optional and used as an
> +	 * optimized fast-path instead of a full mode set operation with all the
> +	 * resulting flickering. If it is not present
> +	 * drm_crtc_helper_set_config() will fall back to a full modeset, using
> +	 * the @mode_set callback. Since it can't update other planes it's
> +	 * incompatible with atomic modeset support.
> +	 *
> +	 * This callback is only used by the CRTC helpers and deprecated.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success or a negative error code on failure.
> +	 */
> +	int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
> +			     struct drm_framebuffer *old_fb);
> +
> +	/**
> +	 * @mode_set_base_atomic:
> +	 *
> +	 * This callback is used by the fbdev helpers to set a new framebuffer
> +	 * and scanout without sleeping, i.e. from an atomic calling context. It
> +	 * is only used to implement kgdb support.
> +	 *
> +	 * This callback is optional and only needed for kgdb support in the fbdev
> +	 * helpers.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success or a negative error code on failure.
> +	 */
> +	int (*mode_set_base_atomic)(struct drm_crtc *crtc,
> +				    struct drm_framebuffer *fb, int x, int y,
> +				    enum mode_set_atomic);
> +
> +	/**
> +	 * @disable:
> +	 *
> +	 * This callback should be used to disable the CRTC. With the atomic
> +	 * drivers it is called after all encoders connected to this CRTC have
> +	 * been shut off already using their own
> +	 * &drm_encoder_helper_funcs.disable hook. If that sequence is too
> +	 * simple drivers can just add their own hooks and call it from this
> +	 * CRTC callback here by looping over all encoders connected to it using
> +	 * for_each_encoder_on_crtc().
> +	 *
> +	 * This hook is used both by legacy CRTC helpers and atomic helpers.
> +	 * Atomic drivers don't need to implement it if there's no need to
> +	 * disable anything at the CRTC level. To ensure that runtime PM
> +	 * handling (using either DPMS or the new "ACTIVE" property) works
> +	 * @disable must be the inverse of @atomic_enable for atomic drivers.
> +	 * Atomic drivers should consider to use @atomic_disable instead of
> +	 * this one.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * With legacy CRTC helpers there's a big semantic difference between
> +	 * @disable and other hooks (like @prepare or @dpms) used to shut down a
> +	 * CRTC: @disable is only called when also logically disabling the
> +	 * display pipeline and needs to release any resources acquired in
> +	 * @mode_set (like shared PLLs, or again release pinned framebuffers).
> +	 *
> +	 * Therefore @disable must be the inverse of @mode_set plus @commit for
> +	 * drivers still using legacy CRTC helpers, which is different from the
> +	 * rules under atomic.
> +	 */
> +	void (*disable)(struct drm_crtc *crtc);
> +
> +	/**
> +	 * @atomic_check:
> +	 *
> +	 * Drivers should check plane-update related CRTC constraints in this
> +	 * hook. They can also check mode related limitations but need to be
> +	 * aware of the calling order, since this hook is used by
> +	 * drm_atomic_helper_check_planes() whereas the preparations needed to
> +	 * check output routing and the display mode is done in
> +	 * drm_atomic_helper_check_modeset(). Therefore drivers that want to
> +	 * check output routing and display mode constraints in this callback
> +	 * must ensure that drm_atomic_helper_check_modeset() has been called
> +	 * beforehand. This is calling order used by the default helper
> +	 * implementation in drm_atomic_helper_check().
> +	 *
> +	 * When using drm_atomic_helper_check_planes() this hook is called
> +	 * after the &drm_plane_helper_funcs.atomic_check hook for planes, which
> +	 * allows drivers to assign shared resources requested by planes in this
> +	 * callback here. For more complicated dependencies the driver can call
> +	 * the provided check helpers multiple times until the computed state
> +	 * has a final configuration and everything has been checked.
> +	 *
> +	 * This function is also allowed to inspect any other object's state and
> +	 * can add more state objects to the atomic commit if needed. Care must
> +	 * be taken though to ensure that state check and compute functions for
> +	 * these added states are all called, and derived state in other objects
> +	 * all updated. Again the recommendation is to just call check helpers
> +	 * until a maximal configuration is reached.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of an atomic update. The
> +	 * driver is not allowed to change anything outside of the free-standing
> +	 * state object passed-in.
> +	 *
> +	 * Also beware that userspace can request its own custom modes, neither
> +	 * core nor helpers filter modes to the list of probe modes reported by
> +	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> +	 * that modes are filtered consistently put any CRTC constraints and
> +	 * limits checks into @mode_valid.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success, -EINVAL if the state or the transition can't be
> +	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> +	 * attempt to obtain another state object ran into a &drm_modeset_lock
> +	 * deadlock.
> +	 */
> +	int (*atomic_check)(struct drm_crtc *crtc,
> +			    struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_begin:
> +	 *
> +	 * Drivers should prepare for an atomic update of multiple planes on
> +	 * a CRTC in this hook. Depending upon hardware this might be vblank
> +	 * evasion, blocking updates by setting bits or doing preparatory work
> +	 * for e.g. manual update display.
> +	 *
> +	 * This hook is called before any plane commit functions are called.
> +	 *
> +	 * Note that the power state of the display pipe when this function is
> +	 * called depends upon the exact helpers and calling sequence the driver
> +	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> +	 * the tradeoffs and variants of plane commit helpers.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional.
> +	 */
> +	void (*atomic_begin)(struct drm_crtc *crtc,
> +			     struct drm_atomic_state *state);
> +	/**
> +	 * @atomic_flush:
> +	 *
> +	 * Drivers should finalize an atomic update of multiple planes on
> +	 * a CRTC in this hook. Depending upon hardware this might include
> +	 * checking that vblank evasion was successful, unblocking updates by
> +	 * setting bits or setting the GO bit to flush out all updates.
> +	 *
> +	 * Simple hardware or hardware with special requirements can commit and
> +	 * flush out all updates for all planes from this hook and forgo all the
> +	 * other commit hooks for plane updates.
> +	 *
> +	 * This hook is called after any plane commit functions are called.
> +	 *
> +	 * Note that the power state of the display pipe when this function is
> +	 * called depends upon the exact helpers and calling sequence the driver
> +	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> +	 * the tradeoffs and variants of plane commit helpers.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional.
> +	 */
> +	void (*atomic_flush)(struct drm_crtc *crtc,
> +			     struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_enable:
> +	 *
> +	 * This callback should be used to enable the CRTC. With the atomic
> +	 * drivers it is called before all encoders connected to this CRTC are
> +	 * enabled through the encoder's own &drm_encoder_helper_funcs.enable
> +	 * hook.  If that sequence is too simple drivers can just add their own
> +	 * hooks and call it from this CRTC callback here by looping over all
> +	 * encoders connected to it using for_each_encoder_on_crtc().
> +	 *
> +	 * This hook is used only by atomic helpers, for symmetry with
> +	 * @atomic_disable. Atomic drivers don't need to implement it if there's
> +	 * no need to enable anything at the CRTC level. To ensure that runtime
> +	 * PM handling (using either DPMS or the new "ACTIVE" property) works
> +	 * @atomic_enable must be the inverse of @atomic_disable for atomic
> +	 * drivers.
> +	 *
> +	 * This function is optional.
> +	 */
> +	void (*atomic_enable)(struct drm_crtc *crtc,
> +			      struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_disable:
> +	 *
> +	 * This callback should be used to disable the CRTC. With the atomic
> +	 * drivers it is called after all encoders connected to this CRTC have
> +	 * been shut off already using their own
> +	 * &drm_encoder_helper_funcs.disable hook. If that sequence is too
> +	 * simple drivers can just add their own hooks and call it from this
> +	 * CRTC callback here by looping over all encoders connected to it using
> +	 * for_each_encoder_on_crtc().
> +	 *
> +	 * This hook is used only by atomic helpers. Atomic drivers don't
> +	 * need to implement it if there's no need to disable anything at the
> +	 * CRTC level.
> +	 *
> +	 * This function is optional.
> +	 */
> +	void (*atomic_disable)(struct drm_crtc *crtc,
> +			       struct drm_atomic_state *state);
> +
> +	/**
> +	 * @get_scanout_position:
> +	 *
> +	 * Called by vblank timestamping code.
> +	 *
> +	 * Returns the current display scanout position from a CRTC and an
> +	 * optional accurate ktime_get() timestamp of when the position was
> +	 * measured. Note that this is a helper callback which is only used
> +	 * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
> +	 * for the @drm_crtc_funcs.get_vblank_timestamp callback.
> +	 *
> +	 * Parameters:
> +	 *
> +	 * crtc:
> +	 *     The CRTC.
> +	 * in_vblank_irq:
> +	 *     True when called from drm_crtc_handle_vblank(). Some drivers
> +	 *     need to apply some workarounds for gpu-specific vblank irq
> +	 *     quirks if the flag is set.
> +	 * vpos:
> +	 *     Target location for current vertical scanout position.
> +	 * hpos:
> +	 *     Target location for current horizontal scanout position.
> +	 * stime:
> +	 *     Target location for timestamp taken immediately before
> +	 *     scanout position query. Can be NULL to skip timestamp.
> +	 * etime:
> +	 *     Target location for timestamp taken immediately after
> +	 *     scanout position query. Can be NULL to skip timestamp.
> +	 * mode:
> +	 *     Current display timings.
> +	 *
> +	 * Returns vpos as a positive number while in active scanout area.
> +	 * Returns vpos as a negative number inside vblank, counting the number
> +	 * of scanlines to go until end of vblank, e.g., -1 means "one scanline
> +	 * until start of active scanout / end of vblank."
> +	 *
> +	 * Returns:
> +	 *
> +	 * True on success, false if a reliable scanout position counter could
> +	 * not be read out.
> +	 */
> +	bool (*get_scanout_position)(struct drm_crtc *crtc,
> +				     bool in_vblank_irq, int *vpos, int *hpos,
> +				     ktime_t *stime, ktime_t *etime,
> +				     const struct drm_display_mode *mode);
> +};
> +
> +/**
> + * drm_crtc_helper_add - sets the helper vtable for a crtc
> + * @crtc: DRM CRTC
> + * @funcs: helper vtable to set for @crtc
> + */
> +static inline void drm_crtc_helper_add(struct drm_crtc *crtc,
> +				       const struct drm_crtc_helper_funcs *funcs)
> +{
> +	crtc->helper_private = funcs;
> +}
> +
> +#endif /* __DRM_CRTC_HELPER_VTABLE_H__ */
> diff --git a/include/drm/drm_encoder_helper_vtable.h b/include/drm/drm_encoder_helper_vtable.h
> new file mode 100644
> index 0000000000000000..434de1ebb829f3ed
> --- /dev/null
> +++ b/include/drm/drm_encoder_helper_vtable.h
> @@ -0,0 +1,381 @@
> +/*
> + * Copyright © 2006 Keith Packard
> + * Copyright © 2007-2008 Dave Airlie
> + * Copyright © 2007-2008 Intel Corporation
> + *   Jesse Barnes <jesse.barnes@...el.com>
> + * Copyright © 2011-2013 Intel Corporation
> + * Copyright © 2015 Intel Corporation
> + *   Daniel Vetter <daniel.vetter@...ll.ch>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __DRM_ENCODER_HELPER_VTABLE_H__
> +#define __DRM_ENCODER_HELPER_VTABLE_H__
> +
> +/**
> + * struct drm_encoder_helper_funcs - helper operations for encoders
> + *
> + * These hooks are used by the legacy CRTC helpers and the new atomic
> + * modesetting helpers.
> + */
> +struct drm_encoder_helper_funcs {
> +	/**
> +	 * @dpms:
> +	 *
> +	 * Callback to control power levels on the encoder.  If the mode passed in
> +	 * is unsupported, the provider must use the next lowest power level.
> +	 * This is used by the legacy encoder helpers to implement DPMS
> +	 * functionality in drm_helper_connector_dpms().
> +	 *
> +	 * This callback is also used to disable an encoder by calling it with
> +	 * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for enabling and disabling an encoder to
> +	 * facilitate transitions to atomic, but it is deprecated. Instead
> +	 * @enable and @disable should be used.
> +	 */
> +	void (*dpms)(struct drm_encoder *encoder, int mode);
> +
> +	/**
> +	 * @mode_valid:
> +	 *
> +	 * This callback is used to check if a specific mode is valid in this
> +	 * encoder. This should be implemented if the encoder has some sort
> +	 * of restriction in the modes it can display. For example, a given
> +	 * encoder may be responsible to set a clock value. If the clock can
> +	 * not produce all the values for the available modes then this callback
> +	 * can be used to restrict the number of modes to only the ones that
> +	 * can be displayed.
> +	 *
> +	 * This hook is used by the probe helpers to filter the mode list in
> +	 * drm_helper_probe_single_connector_modes(), and it is used by the
> +	 * atomic helpers to validate modes supplied by userspace in
> +	 * drm_atomic_helper_check_modeset().
> +	 *
> +	 * This function is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * Since this function is both called from the check phase of an atomic
> +	 * commit, and the mode validation in the probe paths it is not allowed
> +	 * to look at anything else but the passed-in mode, and validate it
> +	 * against configuration-invariant hardware constraints. Any further
> +	 * limits which depend upon the configuration can only be checked in
> +	 * @mode_fixup or @atomic_check.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * drm_mode_status Enum
> +	 */
> +	enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
> +					   const struct drm_display_mode *mode);
> +
> +	/**
> +	 * @mode_fixup:
> +	 *
> +	 * This callback is used to validate and adjust a mode. The parameter
> +	 * mode is the display mode that should be fed to the next element in
> +	 * the display chain, either the final &drm_connector or a &drm_bridge.
> +	 * The parameter adjusted_mode is the input mode the encoder requires. It
> +	 * can be modified by this callback and does not need to match mode. See
> +	 * also &drm_crtc_state.adjusted_mode for more details.
> +	 *
> +	 * This function is used by both legacy CRTC helpers and atomic helpers.
> +	 * This hook is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of atomic modesets, which
> +	 * can be aborted for any reason (including on userspace's request to
> +	 * just check whether a configuration would be possible). Atomic drivers
> +	 * MUST NOT touch any persistent state (hardware or software) or data
> +	 * structures except the passed in adjusted_mode parameter.
> +	 *
> +	 * This is in contrast to the legacy CRTC helpers where this was
> +	 * allowed.
> +	 *
> +	 * Atomic drivers which need to inspect and adjust more state should
> +	 * instead use the @atomic_check callback. If @atomic_check is used,
> +	 * this hook isn't called since @atomic_check allows a strict superset
> +	 * of the functionality of @mode_fixup.
> +	 *
> +	 * Also beware that userspace can request its own custom modes, neither
> +	 * core nor helpers filter modes to the list of probe modes reported by
> +	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> +	 * that modes are filtered consistently put any encoder constraints and
> +	 * limits checks into @mode_valid.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * True if an acceptable configuration is possible, false if the modeset
> +	 * operation should be rejected.
> +	 */
> +	bool (*mode_fixup)(struct drm_encoder *encoder,
> +			   const struct drm_display_mode *mode,
> +			   struct drm_display_mode *adjusted_mode);
> +
> +	/**
> +	 * @prepare:
> +	 *
> +	 * This callback should prepare the encoder for a subsequent modeset,
> +	 * which in practice means the driver should disable the encoder if it
> +	 * is running. Most drivers ended up implementing this by calling their
> +	 * @dpms hook with DRM_MODE_DPMS_OFF.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for disabling an encoder to facilitate
> +	 * transitions to atomic, but it is deprecated. Instead @disable should
> +	 * be used.
> +	 */
> +	void (*prepare)(struct drm_encoder *encoder);
> +
> +	/**
> +	 * @commit:
> +	 *
> +	 * This callback should commit the new mode on the encoder after a modeset,
> +	 * which in practice means the driver should enable the encoder.  Most
> +	 * drivers ended up implementing this by calling their @dpms hook with
> +	 * DRM_MODE_DPMS_ON.
> +	 *
> +	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> +	 * also support using this hook for enabling an encoder to facilitate
> +	 * transitions to atomic, but it is deprecated. Instead @enable should
> +	 * be used.
> +	 */
> +	void (*commit)(struct drm_encoder *encoder);
> +
> +	/**
> +	 * @mode_set:
> +	 *
> +	 * This callback is used to update the display mode of an encoder.
> +	 *
> +	 * Note that the display pipe is completely off when this function is
> +	 * called. Drivers which need hardware to be running before they program
> +	 * the new display mode (because they implement runtime PM) should not
> +	 * use this hook, because the helper library calls it only once and not
> +	 * every time the display pipeline is suspend using either DPMS or the
> +	 * new "ACTIVE" property. Such drivers should instead move all their
> +	 * encoder setup into the @enable callback.
> +	 *
> +	 * This callback is used both by the legacy CRTC helpers and the atomic
> +	 * modeset helpers. It is optional in the atomic helpers.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * If the driver uses the atomic modeset helpers and needs to inspect
> +	 * the connector state or connector display info during mode setting,
> +	 * @atomic_mode_set can be used instead.
> +	 */
> +	void (*mode_set)(struct drm_encoder *encoder,
> +			 struct drm_display_mode *mode,
> +			 struct drm_display_mode *adjusted_mode);
> +
> +	/**
> +	 * @atomic_mode_set:
> +	 *
> +	 * This callback is used to update the display mode of an encoder.
> +	 *
> +	 * Note that the display pipe is completely off when this function is
> +	 * called. Drivers which need hardware to be running before they program
> +	 * the new display mode (because they implement runtime PM) should not
> +	 * use this hook, because the helper library calls it only once and not
> +	 * every time the display pipeline is suspended using either DPMS or the
> +	 * new "ACTIVE" property. Such drivers should instead move all their
> +	 * encoder setup into the @enable callback.
> +	 *
> +	 * This callback is used by the atomic modeset helpers in place of the
> +	 * @mode_set callback, if set by the driver. It is optional and should
> +	 * be used instead of @mode_set if the driver needs to inspect the
> +	 * connector state or display info, since there is no direct way to
> +	 * go from the encoder to the current connector.
> +	 */
> +	void (*atomic_mode_set)(struct drm_encoder *encoder,
> +				struct drm_crtc_state *crtc_state,
> +				struct drm_connector_state *conn_state);
> +
> +	/**
> +	 * @detect:
> +	 *
> +	 * This callback can be used by drivers who want to do detection on the
> +	 * encoder object instead of in connector functions.
> +	 *
> +	 * It is not used by any helper and therefore has purely driver-specific
> +	 * semantics. New drivers shouldn't use this and instead just implement
> +	 * their own private callbacks.
> +	 *
> +	 * FIXME:
> +	 *
> +	 * This should just be converted into a pile of driver vfuncs.
> +	 * Currently radeon, amdgpu and nouveau are using it.
> +	 */
> +	enum drm_connector_status (*detect)(struct drm_encoder *encoder,
> +					    struct drm_connector *connector);
> +
> +	/**
> +	 * @atomic_disable:
> +	 *
> +	 * This callback should be used to disable the encoder. With the atomic
> +	 * drivers it is called before this encoder's CRTC has been shut off
> +	 * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
> +	 * sequence is too simple drivers can just add their own driver private
> +	 * encoder hooks and call them from CRTC's callback by looping over all
> +	 * encoders connected to it using for_each_encoder_on_crtc().
> +	 *
> +	 * This callback is a variant of @disable that provides the atomic state
> +	 * to the driver. If @atomic_disable is implemented, @disable is not
> +	 * called by the helpers.
> +	 *
> +	 * This hook is only used by atomic helpers. Atomic drivers don't need
> +	 * to implement it if there's no need to disable anything at the encoder
> +	 * level. To ensure that runtime PM handling (using either DPMS or the
> +	 * new "ACTIVE" property) works @atomic_disable must be the inverse of
> +	 * @atomic_enable.
> +	 */
> +	void (*atomic_disable)(struct drm_encoder *encoder,
> +			       struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_enable:
> +	 *
> +	 * This callback should be used to enable the encoder. It is called
> +	 * after this encoder's CRTC has been enabled using their own
> +	 * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
> +	 * too simple drivers can just add their own driver private encoder
> +	 * hooks and call them from CRTC's callback by looping over all encoders
> +	 * connected to it using for_each_encoder_on_crtc().
> +	 *
> +	 * This callback is a variant of @enable that provides the atomic state
> +	 * to the driver. If @atomic_enable is implemented, @enable is not
> +	 * called by the helpers.
> +	 *
> +	 * This hook is only used by atomic helpers, it is the opposite of
> +	 * @atomic_disable. Atomic drivers don't need to implement it if there's
> +	 * no need to enable anything at the encoder level. To ensure that
> +	 * runtime PM handling works @atomic_enable must be the inverse of
> +	 * @atomic_disable.
> +	 */
> +	void (*atomic_enable)(struct drm_encoder *encoder,
> +			      struct drm_atomic_state *state);
> +
> +	/**
> +	 * @disable:
> +	 *
> +	 * This callback should be used to disable the encoder. With the atomic
> +	 * drivers it is called before this encoder's CRTC has been shut off
> +	 * using their own &drm_crtc_helper_funcs.disable hook.  If that
> +	 * sequence is too simple drivers can just add their own driver private
> +	 * encoder hooks and call them from CRTC's callback by looping over all
> +	 * encoders connected to it using for_each_encoder_on_crtc().
> +	 *
> +	 * This hook is used both by legacy CRTC helpers and atomic helpers.
> +	 * Atomic drivers don't need to implement it if there's no need to
> +	 * disable anything at the encoder level. To ensure that runtime PM
> +	 * handling (using either DPMS or the new "ACTIVE" property) works
> +	 * @disable must be the inverse of @enable for atomic drivers.
> +	 *
> +	 * For atomic drivers also consider @atomic_disable and save yourself
> +	 * from having to read the NOTE below!
> +	 *
> +	 * NOTE:
> +	 *
> +	 * With legacy CRTC helpers there's a big semantic difference between
> +	 * @disable and other hooks (like @prepare or @dpms) used to shut down a
> +	 * encoder: @disable is only called when also logically disabling the
> +	 * display pipeline and needs to release any resources acquired in
> +	 * @mode_set (like shared PLLs, or again release pinned framebuffers).
> +	 *
> +	 * Therefore @disable must be the inverse of @mode_set plus @commit for
> +	 * drivers still using legacy CRTC helpers, which is different from the
> +	 * rules under atomic.
> +	 */
> +	void (*disable)(struct drm_encoder *encoder);
> +
> +	/**
> +	 * @enable:
> +	 *
> +	 * This callback should be used to enable the encoder. With the atomic
> +	 * drivers it is called after this encoder's CRTC has been enabled using
> +	 * their own &drm_crtc_helper_funcs.enable hook.  If that sequence is
> +	 * too simple drivers can just add their own driver private encoder
> +	 * hooks and call them from CRTC's callback by looping over all encoders
> +	 * connected to it using for_each_encoder_on_crtc().
> +	 *
> +	 * This hook is only used by atomic helpers, it is the opposite of
> +	 * @disable. Atomic drivers don't need to implement it if there's no
> +	 * need to enable anything at the encoder level. To ensure that
> +	 * runtime PM handling (using either DPMS or the new "ACTIVE" property)
> +	 * works @enable must be the inverse of @disable for atomic drivers.
> +	 */
> +	void (*enable)(struct drm_encoder *encoder);
> +
> +	/**
> +	 * @atomic_check:
> +	 *
> +	 * This callback is used to validate encoder state for atomic drivers.
> +	 * Since the encoder is the object connecting the CRTC and connector it
> +	 * gets passed both states, to be able to validate interactions and
> +	 * update the CRTC to match what the encoder needs for the requested
> +	 * connector.
> +	 *
> +	 * Since this provides a strict superset of the functionality of
> +	 * @mode_fixup (the requested and adjusted modes are both available
> +	 * through the passed in &struct drm_crtc_state) @mode_fixup is not
> +	 * called when @atomic_check is implemented.
> +	 *
> +	 * This function is used by the atomic helpers, but it is optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of an atomic update. The
> +	 * driver is not allowed to change anything outside of the free-standing
> +	 * state objects passed-in or assembled in the overall &drm_atomic_state
> +	 * update tracking structure.
> +	 *
> +	 * Also beware that userspace can request its own custom modes, neither
> +	 * core nor helpers filter modes to the list of probe modes reported by
> +	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> +	 * that modes are filtered consistently put any encoder constraints and
> +	 * limits checks into @mode_valid.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success, -EINVAL if the state or the transition can't be
> +	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> +	 * attempt to obtain another state object ran into a &drm_modeset_lock
> +	 * deadlock.
> +	 */
> +	int (*atomic_check)(struct drm_encoder *encoder,
> +			    struct drm_crtc_state *crtc_state,
> +			    struct drm_connector_state *conn_state);
> +};
> +
> +/**
> + * drm_encoder_helper_add - sets the helper vtable for an encoder
> + * @encoder: DRM encoder
> + * @funcs: helper vtable to set for @encoder
> + */
> +static inline void drm_encoder_helper_add(struct drm_encoder *encoder,
> +					  const struct drm_encoder_helper_funcs *funcs)
> +{
> +	encoder->helper_private = funcs;
> +}
> +
> +#endif /* __DRM_ENCODER_HELPER_VTABLE_H__ */
> diff --git a/include/drm/drm_mode_config_helper_vtable.h b/include/drm/drm_mode_config_helper_vtable.h
> new file mode 100644
> index 0000000000000000..a56e3490e27411de
> --- /dev/null
> +++ b/include/drm/drm_mode_config_helper_vtable.h
> @@ -0,0 +1,97 @@
> +/*
> + * Copyright © 2006 Keith Packard
> + * Copyright © 2007-2008 Dave Airlie
> + * Copyright © 2007-2008 Intel Corporation
> + *   Jesse Barnes <jesse.barnes@...el.com>
> + * Copyright © 2011-2013 Intel Corporation
> + * Copyright © 2015 Intel Corporation
> + *   Daniel Vetter <daniel.vetter@...ll.ch>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __DRM_MODE_CONFIG_HELPER_VTABLE_H__
> +#define __DRM_MODE_CONFIG_HELPER_VTABLE_H__
> +
> +/**
> + * struct drm_mode_config_helper_funcs - global modeset helper operations
> + *
> + * These helper functions are used by the atomic helpers.
> + */
> +struct drm_mode_config_helper_funcs {
> +	/**
> +	 * @atomic_commit_tail:
> +	 *
> +	 * This hook is used by the default atomic_commit() hook implemented in
> +	 * drm_atomic_helper_commit() together with the nonblocking commit
> +	 * helpers (see drm_atomic_helper_setup_commit() for a starting point)
> +	 * to implement blocking and nonblocking commits easily. It is not used
> +	 * by the atomic helpers
> +	 *
> +	 * This function is called when the new atomic state has already been
> +	 * swapped into the various state pointers. The passed in state
> +	 * therefore contains copies of the old/previous state. This hook should
> +	 * commit the new state into hardware. Note that the helpers have
> +	 * already waited for preceding atomic commits and fences, but drivers
> +	 * can add more waiting calls at the start of their implementation, e.g.
> +	 * to wait for driver-internal request for implicit syncing, before
> +	 * starting to commit the update to the hardware.
> +	 *
> +	 * After the atomic update is committed to the hardware this hook needs
> +	 * to call drm_atomic_helper_commit_hw_done(). Then wait for the update
> +	 * to be executed by the hardware, for example using
> +	 * drm_atomic_helper_wait_for_vblanks() or
> +	 * drm_atomic_helper_wait_for_flip_done(), and then clean up the old
> +	 * framebuffers using drm_atomic_helper_cleanup_planes().
> +	 *
> +	 * When disabling a CRTC this hook _must_ stall for the commit to
> +	 * complete. Vblank waits don't work on disabled CRTC, hence the core
> +	 * can't take care of this. And it also can't rely on the vblank event,
> +	 * since that can be signalled already when the screen shows black,
> +	 * which can happen much earlier than the last hardware access needed to
> +	 * shut off the display pipeline completely.
> +	 *
> +	 * This hook is optional, the default implementation is
> +	 * drm_atomic_helper_commit_tail().
> +	 */
> +	void (*atomic_commit_tail)(struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_commit_setup:
> +	 *
> +	 * This hook is used by the default atomic_commit() hook implemented in
> +	 * drm_atomic_helper_commit() together with the nonblocking helpers (see
> +	 * drm_atomic_helper_setup_commit()) to extend the DRM commit setup. It
> +	 * is not used by the atomic helpers.
> +	 *
> +	 * This function is called at the end of
> +	 * drm_atomic_helper_setup_commit(), so once the commit has been
> +	 * properly setup across the generic DRM object states. It allows
> +	 * drivers to do some additional commit tracking that isn't related to a
> +	 * CRTC, plane or connector, tracked in a &drm_private_obj structure.
> +	 *
> +	 * Note that the documentation of &drm_private_obj has more details on
> +	 * how one should implement this.
> +	 *
> +	 * This hook is optional.
> +	 */
> +	int (*atomic_commit_setup)(struct drm_atomic_state *state);
> +};
> +
> +#endif /* __DRM_MODE_CONFIG_HELPER_VTABLE_H__ */
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index 91860372be6c064e..a9fb43b07b60872d 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -48,1466 +48,10 @@
>    * To make this clear all the helper vtables are pulled together in this location here.
>    */
>   
> -struct drm_writeback_connector;
> -struct drm_writeback_job;
> -
> -enum mode_set_atomic {
> -	LEAVE_ATOMIC_MODE_SET,
> -	ENTER_ATOMIC_MODE_SET,
> -};
> -
> -/**
> - * struct drm_crtc_helper_funcs - helper operations for CRTCs
> - *
> - * These hooks are used by the legacy CRTC helpers and the new atomic
> - * modesetting helpers.
> - */
> -struct drm_crtc_helper_funcs {
> -	/**
> -	 * @dpms:
> -	 *
> -	 * Callback to control power levels on the CRTC.  If the mode passed in
> -	 * is unsupported, the provider must use the next lowest power level.
> -	 * This is used by the legacy CRTC helpers to implement DPMS
> -	 * functionality in drm_helper_connector_dpms().
> -	 *
> -	 * This callback is also used to disable a CRTC by calling it with
> -	 * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for enabling and disabling a CRTC to
> -	 * facilitate transitions to atomic, but it is deprecated. Instead
> -	 * @atomic_enable and @atomic_disable should be used.
> -	 */
> -	void (*dpms)(struct drm_crtc *crtc, int mode);
> -
> -	/**
> -	 * @prepare:
> -	 *
> -	 * This callback should prepare the CRTC for a subsequent modeset, which
> -	 * in practice means the driver should disable the CRTC if it is
> -	 * running. Most drivers ended up implementing this by calling their
> -	 * @dpms hook with DRM_MODE_DPMS_OFF.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for disabling a CRTC to facilitate
> -	 * transitions to atomic, but it is deprecated. Instead @atomic_disable
> -	 * should be used.
> -	 */
> -	void (*prepare)(struct drm_crtc *crtc);
> -
> -	/**
> -	 * @commit:
> -	 *
> -	 * This callback should commit the new mode on the CRTC after a modeset,
> -	 * which in practice means the driver should enable the CRTC.  Most
> -	 * drivers ended up implementing this by calling their @dpms hook with
> -	 * DRM_MODE_DPMS_ON.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for enabling a CRTC to facilitate
> -	 * transitions to atomic, but it is deprecated. Instead @atomic_enable
> -	 * should be used.
> -	 */
> -	void (*commit)(struct drm_crtc *crtc);
> -
> -	/**
> -	 * @mode_valid:
> -	 *
> -	 * This callback is used to check if a specific mode is valid in this
> -	 * crtc. This should be implemented if the crtc has some sort of
> -	 * restriction in the modes it can display. For example, a given crtc
> -	 * may be responsible to set a clock value. If the clock can not
> -	 * produce all the values for the available modes then this callback
> -	 * can be used to restrict the number of modes to only the ones that
> -	 * can be displayed.
> -	 *
> -	 * This hook is used by the probe helpers to filter the mode list in
> -	 * drm_helper_probe_single_connector_modes(), and it is used by the
> -	 * atomic helpers to validate modes supplied by userspace in
> -	 * drm_atomic_helper_check_modeset().
> -	 *
> -	 * This function is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * Since this function is both called from the check phase of an atomic
> -	 * commit, and the mode validation in the probe paths it is not allowed
> -	 * to look at anything else but the passed-in mode, and validate it
> -	 * against configuration-invariant hardware constraints. Any further
> -	 * limits which depend upon the configuration can only be checked in
> -	 * @mode_fixup or @atomic_check.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * drm_mode_status Enum
> -	 */
> -	enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
> -					   const struct drm_display_mode *mode);
> -
> -	/**
> -	 * @mode_fixup:
> -	 *
> -	 * This callback is used to validate a mode. The parameter mode is the
> -	 * display mode that userspace requested, adjusted_mode is the mode the
> -	 * encoders need to be fed with. Note that this is the inverse semantics
> -	 * of the meaning for the &drm_encoder and &drm_bridge_funcs.mode_fixup
> -	 * vfunc. If the CRTC cannot support the requested conversion from mode
> -	 * to adjusted_mode it should reject the modeset. See also
> -	 * &drm_crtc_state.adjusted_mode for more details.
> -	 *
> -	 * This function is used by both legacy CRTC helpers and atomic helpers.
> -	 * With atomic helpers it is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of atomic modesets, which
> -	 * can be aborted for any reason (including on userspace's request to
> -	 * just check whether a configuration would be possible). Atomic drivers
> -	 * MUST NOT touch any persistent state (hardware or software) or data
> -	 * structures except the passed in adjusted_mode parameter.
> -	 *
> -	 * This is in contrast to the legacy CRTC helpers where this was
> -	 * allowed.
> -	 *
> -	 * Atomic drivers which need to inspect and adjust more state should
> -	 * instead use the @atomic_check callback, but note that they're not
> -	 * perfectly equivalent: @mode_valid is called from
> -	 * drm_atomic_helper_check_modeset(), but @atomic_check is called from
> -	 * drm_atomic_helper_check_planes(), because originally it was meant for
> -	 * plane update checks only.
> -	 *
> -	 * Also beware that userspace can request its own custom modes, neither
> -	 * core nor helpers filter modes to the list of probe modes reported by
> -	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> -	 * that modes are filtered consistently put any CRTC constraints and
> -	 * limits checks into @mode_valid.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * True if an acceptable configuration is possible, false if the modeset
> -	 * operation should be rejected.
> -	 */
> -	bool (*mode_fixup)(struct drm_crtc *crtc,
> -			   const struct drm_display_mode *mode,
> -			   struct drm_display_mode *adjusted_mode);
> -
> -	/**
> -	 * @mode_set:
> -	 *
> -	 * This callback is used by the legacy CRTC helpers to set a new mode,
> -	 * position and framebuffer. Since it ties the primary plane to every
> -	 * mode change it is incompatible with universal plane support. And
> -	 * since it can't update other planes it's incompatible with atomic
> -	 * modeset support.
> -	 *
> -	 * This callback is only used by CRTC helpers and deprecated.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success or a negative error code on failure.
> -	 */
> -	int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
> -			struct drm_display_mode *adjusted_mode, int x, int y,
> -			struct drm_framebuffer *old_fb);
> -
> -	/**
> -	 * @mode_set_nofb:
> -	 *
> -	 * This callback is used to update the display mode of a CRTC without
> -	 * changing anything of the primary plane configuration. This fits the
> -	 * requirement of atomic and hence is used by the atomic helpers.
> -	 *
> -	 * Note that the display pipe is completely off when this function is
> -	 * called. Atomic drivers which need hardware to be running before they
> -	 * program the new display mode (e.g. because they implement runtime PM)
> -	 * should not use this hook. This is because the helper library calls
> -	 * this hook only once per mode change and not every time the display
> -	 * pipeline is suspended using either DPMS or the new "ACTIVE" property.
> -	 * Which means register values set in this callback might get reset when
> -	 * the CRTC is suspended, but not restored.  Such drivers should instead
> -	 * move all their CRTC setup into the @atomic_enable callback.
> -	 *
> -	 * This callback is optional.
> -	 */
> -	void (*mode_set_nofb)(struct drm_crtc *crtc);
> -
> -	/**
> -	 * @mode_set_base:
> -	 *
> -	 * This callback is used by the legacy CRTC helpers to set a new
> -	 * framebuffer and scanout position. It is optional and used as an
> -	 * optimized fast-path instead of a full mode set operation with all the
> -	 * resulting flickering. If it is not present
> -	 * drm_crtc_helper_set_config() will fall back to a full modeset, using
> -	 * the @mode_set callback. Since it can't update other planes it's
> -	 * incompatible with atomic modeset support.
> -	 *
> -	 * This callback is only used by the CRTC helpers and deprecated.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success or a negative error code on failure.
> -	 */
> -	int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
> -			     struct drm_framebuffer *old_fb);
> -
> -	/**
> -	 * @mode_set_base_atomic:
> -	 *
> -	 * This callback is used by the fbdev helpers to set a new framebuffer
> -	 * and scanout without sleeping, i.e. from an atomic calling context. It
> -	 * is only used to implement kgdb support.
> -	 *
> -	 * This callback is optional and only needed for kgdb support in the fbdev
> -	 * helpers.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success or a negative error code on failure.
> -	 */
> -	int (*mode_set_base_atomic)(struct drm_crtc *crtc,
> -				    struct drm_framebuffer *fb, int x, int y,
> -				    enum mode_set_atomic);
> -
> -	/**
> -	 * @disable:
> -	 *
> -	 * This callback should be used to disable the CRTC. With the atomic
> -	 * drivers it is called after all encoders connected to this CRTC have
> -	 * been shut off already using their own
> -	 * &drm_encoder_helper_funcs.disable hook. If that sequence is too
> -	 * simple drivers can just add their own hooks and call it from this
> -	 * CRTC callback here by looping over all encoders connected to it using
> -	 * for_each_encoder_on_crtc().
> -	 *
> -	 * This hook is used both by legacy CRTC helpers and atomic helpers.
> -	 * Atomic drivers don't need to implement it if there's no need to
> -	 * disable anything at the CRTC level. To ensure that runtime PM
> -	 * handling (using either DPMS or the new "ACTIVE" property) works
> -	 * @disable must be the inverse of @atomic_enable for atomic drivers.
> -	 * Atomic drivers should consider to use @atomic_disable instead of
> -	 * this one.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * With legacy CRTC helpers there's a big semantic difference between
> -	 * @disable and other hooks (like @prepare or @dpms) used to shut down a
> -	 * CRTC: @disable is only called when also logically disabling the
> -	 * display pipeline and needs to release any resources acquired in
> -	 * @mode_set (like shared PLLs, or again release pinned framebuffers).
> -	 *
> -	 * Therefore @disable must be the inverse of @mode_set plus @commit for
> -	 * drivers still using legacy CRTC helpers, which is different from the
> -	 * rules under atomic.
> -	 */
> -	void (*disable)(struct drm_crtc *crtc);
> -
> -	/**
> -	 * @atomic_check:
> -	 *
> -	 * Drivers should check plane-update related CRTC constraints in this
> -	 * hook. They can also check mode related limitations but need to be
> -	 * aware of the calling order, since this hook is used by
> -	 * drm_atomic_helper_check_planes() whereas the preparations needed to
> -	 * check output routing and the display mode is done in
> -	 * drm_atomic_helper_check_modeset(). Therefore drivers that want to
> -	 * check output routing and display mode constraints in this callback
> -	 * must ensure that drm_atomic_helper_check_modeset() has been called
> -	 * beforehand. This is calling order used by the default helper
> -	 * implementation in drm_atomic_helper_check().
> -	 *
> -	 * When using drm_atomic_helper_check_planes() this hook is called
> -	 * after the &drm_plane_helper_funcs.atomic_check hook for planes, which
> -	 * allows drivers to assign shared resources requested by planes in this
> -	 * callback here. For more complicated dependencies the driver can call
> -	 * the provided check helpers multiple times until the computed state
> -	 * has a final configuration and everything has been checked.
> -	 *
> -	 * This function is also allowed to inspect any other object's state and
> -	 * can add more state objects to the atomic commit if needed. Care must
> -	 * be taken though to ensure that state check and compute functions for
> -	 * these added states are all called, and derived state in other objects
> -	 * all updated. Again the recommendation is to just call check helpers
> -	 * until a maximal configuration is reached.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of an atomic update. The
> -	 * driver is not allowed to change anything outside of the free-standing
> -	 * state object passed-in.
> -	 *
> -	 * Also beware that userspace can request its own custom modes, neither
> -	 * core nor helpers filter modes to the list of probe modes reported by
> -	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> -	 * that modes are filtered consistently put any CRTC constraints and
> -	 * limits checks into @mode_valid.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success, -EINVAL if the state or the transition can't be
> -	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> -	 * attempt to obtain another state object ran into a &drm_modeset_lock
> -	 * deadlock.
> -	 */
> -	int (*atomic_check)(struct drm_crtc *crtc,
> -			    struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_begin:
> -	 *
> -	 * Drivers should prepare for an atomic update of multiple planes on
> -	 * a CRTC in this hook. Depending upon hardware this might be vblank
> -	 * evasion, blocking updates by setting bits or doing preparatory work
> -	 * for e.g. manual update display.
> -	 *
> -	 * This hook is called before any plane commit functions are called.
> -	 *
> -	 * Note that the power state of the display pipe when this function is
> -	 * called depends upon the exact helpers and calling sequence the driver
> -	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> -	 * the tradeoffs and variants of plane commit helpers.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional.
> -	 */
> -	void (*atomic_begin)(struct drm_crtc *crtc,
> -			     struct drm_atomic_state *state);
> -	/**
> -	 * @atomic_flush:
> -	 *
> -	 * Drivers should finalize an atomic update of multiple planes on
> -	 * a CRTC in this hook. Depending upon hardware this might include
> -	 * checking that vblank evasion was successful, unblocking updates by
> -	 * setting bits or setting the GO bit to flush out all updates.
> -	 *
> -	 * Simple hardware or hardware with special requirements can commit and
> -	 * flush out all updates for all planes from this hook and forgo all the
> -	 * other commit hooks for plane updates.
> -	 *
> -	 * This hook is called after any plane commit functions are called.
> -	 *
> -	 * Note that the power state of the display pipe when this function is
> -	 * called depends upon the exact helpers and calling sequence the driver
> -	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> -	 * the tradeoffs and variants of plane commit helpers.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional.
> -	 */
> -	void (*atomic_flush)(struct drm_crtc *crtc,
> -			     struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_enable:
> -	 *
> -	 * This callback should be used to enable the CRTC. With the atomic
> -	 * drivers it is called before all encoders connected to this CRTC are
> -	 * enabled through the encoder's own &drm_encoder_helper_funcs.enable
> -	 * hook.  If that sequence is too simple drivers can just add their own
> -	 * hooks and call it from this CRTC callback here by looping over all
> -	 * encoders connected to it using for_each_encoder_on_crtc().
> -	 *
> -	 * This hook is used only by atomic helpers, for symmetry with
> -	 * @atomic_disable. Atomic drivers don't need to implement it if there's
> -	 * no need to enable anything at the CRTC level. To ensure that runtime
> -	 * PM handling (using either DPMS or the new "ACTIVE" property) works
> -	 * @atomic_enable must be the inverse of @atomic_disable for atomic
> -	 * drivers.
> -	 *
> -	 * This function is optional.
> -	 */
> -	void (*atomic_enable)(struct drm_crtc *crtc,
> -			      struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_disable:
> -	 *
> -	 * This callback should be used to disable the CRTC. With the atomic
> -	 * drivers it is called after all encoders connected to this CRTC have
> -	 * been shut off already using their own
> -	 * &drm_encoder_helper_funcs.disable hook. If that sequence is too
> -	 * simple drivers can just add their own hooks and call it from this
> -	 * CRTC callback here by looping over all encoders connected to it using
> -	 * for_each_encoder_on_crtc().
> -	 *
> -	 * This hook is used only by atomic helpers. Atomic drivers don't
> -	 * need to implement it if there's no need to disable anything at the
> -	 * CRTC level.
> -	 *
> -	 * This function is optional.
> -	 */
> -	void (*atomic_disable)(struct drm_crtc *crtc,
> -			       struct drm_atomic_state *state);
> -
> -	/**
> -	 * @get_scanout_position:
> -	 *
> -	 * Called by vblank timestamping code.
> -	 *
> -	 * Returns the current display scanout position from a CRTC and an
> -	 * optional accurate ktime_get() timestamp of when the position was
> -	 * measured. Note that this is a helper callback which is only used
> -	 * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
> -	 * for the @drm_crtc_funcs.get_vblank_timestamp callback.
> -	 *
> -	 * Parameters:
> -	 *
> -	 * crtc:
> -	 *     The CRTC.
> -	 * in_vblank_irq:
> -	 *     True when called from drm_crtc_handle_vblank(). Some drivers
> -	 *     need to apply some workarounds for gpu-specific vblank irq
> -	 *     quirks if the flag is set.
> -	 * vpos:
> -	 *     Target location for current vertical scanout position.
> -	 * hpos:
> -	 *     Target location for current horizontal scanout position.
> -	 * stime:
> -	 *     Target location for timestamp taken immediately before
> -	 *     scanout position query. Can be NULL to skip timestamp.
> -	 * etime:
> -	 *     Target location for timestamp taken immediately after
> -	 *     scanout position query. Can be NULL to skip timestamp.
> -	 * mode:
> -	 *     Current display timings.
> -	 *
> -	 * Returns vpos as a positive number while in active scanout area.
> -	 * Returns vpos as a negative number inside vblank, counting the number
> -	 * of scanlines to go until end of vblank, e.g., -1 means "one scanline
> -	 * until start of active scanout / end of vblank."
> -	 *
> -	 * Returns:
> -	 *
> -	 * True on success, false if a reliable scanout position counter could
> -	 * not be read out.
> -	 */
> -	bool (*get_scanout_position)(struct drm_crtc *crtc,
> -				     bool in_vblank_irq, int *vpos, int *hpos,
> -				     ktime_t *stime, ktime_t *etime,
> -				     const struct drm_display_mode *mode);
> -};
> -
> -/**
> - * drm_crtc_helper_add - sets the helper vtable for a crtc
> - * @crtc: DRM CRTC
> - * @funcs: helper vtable to set for @crtc
> - */
> -static inline void drm_crtc_helper_add(struct drm_crtc *crtc,
> -				       const struct drm_crtc_helper_funcs *funcs)
> -{
> -	crtc->helper_private = funcs;
> -}
> -
> -/**
> - * struct drm_encoder_helper_funcs - helper operations for encoders
> - *
> - * These hooks are used by the legacy CRTC helpers and the new atomic
> - * modesetting helpers.
> - */
> -struct drm_encoder_helper_funcs {
> -	/**
> -	 * @dpms:
> -	 *
> -	 * Callback to control power levels on the encoder.  If the mode passed in
> -	 * is unsupported, the provider must use the next lowest power level.
> -	 * This is used by the legacy encoder helpers to implement DPMS
> -	 * functionality in drm_helper_connector_dpms().
> -	 *
> -	 * This callback is also used to disable an encoder by calling it with
> -	 * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for enabling and disabling an encoder to
> -	 * facilitate transitions to atomic, but it is deprecated. Instead
> -	 * @enable and @disable should be used.
> -	 */
> -	void (*dpms)(struct drm_encoder *encoder, int mode);
> -
> -	/**
> -	 * @mode_valid:
> -	 *
> -	 * This callback is used to check if a specific mode is valid in this
> -	 * encoder. This should be implemented if the encoder has some sort
> -	 * of restriction in the modes it can display. For example, a given
> -	 * encoder may be responsible to set a clock value. If the clock can
> -	 * not produce all the values for the available modes then this callback
> -	 * can be used to restrict the number of modes to only the ones that
> -	 * can be displayed.
> -	 *
> -	 * This hook is used by the probe helpers to filter the mode list in
> -	 * drm_helper_probe_single_connector_modes(), and it is used by the
> -	 * atomic helpers to validate modes supplied by userspace in
> -	 * drm_atomic_helper_check_modeset().
> -	 *
> -	 * This function is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * Since this function is both called from the check phase of an atomic
> -	 * commit, and the mode validation in the probe paths it is not allowed
> -	 * to look at anything else but the passed-in mode, and validate it
> -	 * against configuration-invariant hardware constraints. Any further
> -	 * limits which depend upon the configuration can only be checked in
> -	 * @mode_fixup or @atomic_check.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * drm_mode_status Enum
> -	 */
> -	enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
> -					   const struct drm_display_mode *mode);
> -
> -	/**
> -	 * @mode_fixup:
> -	 *
> -	 * This callback is used to validate and adjust a mode. The parameter
> -	 * mode is the display mode that should be fed to the next element in
> -	 * the display chain, either the final &drm_connector or a &drm_bridge.
> -	 * The parameter adjusted_mode is the input mode the encoder requires. It
> -	 * can be modified by this callback and does not need to match mode. See
> -	 * also &drm_crtc_state.adjusted_mode for more details.
> -	 *
> -	 * This function is used by both legacy CRTC helpers and atomic helpers.
> -	 * This hook is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of atomic modesets, which
> -	 * can be aborted for any reason (including on userspace's request to
> -	 * just check whether a configuration would be possible). Atomic drivers
> -	 * MUST NOT touch any persistent state (hardware or software) or data
> -	 * structures except the passed in adjusted_mode parameter.
> -	 *
> -	 * This is in contrast to the legacy CRTC helpers where this was
> -	 * allowed.
> -	 *
> -	 * Atomic drivers which need to inspect and adjust more state should
> -	 * instead use the @atomic_check callback. If @atomic_check is used,
> -	 * this hook isn't called since @atomic_check allows a strict superset
> -	 * of the functionality of @mode_fixup.
> -	 *
> -	 * Also beware that userspace can request its own custom modes, neither
> -	 * core nor helpers filter modes to the list of probe modes reported by
> -	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> -	 * that modes are filtered consistently put any encoder constraints and
> -	 * limits checks into @mode_valid.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * True if an acceptable configuration is possible, false if the modeset
> -	 * operation should be rejected.
> -	 */
> -	bool (*mode_fixup)(struct drm_encoder *encoder,
> -			   const struct drm_display_mode *mode,
> -			   struct drm_display_mode *adjusted_mode);
> -
> -	/**
> -	 * @prepare:
> -	 *
> -	 * This callback should prepare the encoder for a subsequent modeset,
> -	 * which in practice means the driver should disable the encoder if it
> -	 * is running. Most drivers ended up implementing this by calling their
> -	 * @dpms hook with DRM_MODE_DPMS_OFF.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for disabling an encoder to facilitate
> -	 * transitions to atomic, but it is deprecated. Instead @disable should
> -	 * be used.
> -	 */
> -	void (*prepare)(struct drm_encoder *encoder);
> -
> -	/**
> -	 * @commit:
> -	 *
> -	 * This callback should commit the new mode on the encoder after a modeset,
> -	 * which in practice means the driver should enable the encoder.  Most
> -	 * drivers ended up implementing this by calling their @dpms hook with
> -	 * DRM_MODE_DPMS_ON.
> -	 *
> -	 * This callback is used by the legacy CRTC helpers.  Atomic helpers
> -	 * also support using this hook for enabling an encoder to facilitate
> -	 * transitions to atomic, but it is deprecated. Instead @enable should
> -	 * be used.
> -	 */
> -	void (*commit)(struct drm_encoder *encoder);
> -
> -	/**
> -	 * @mode_set:
> -	 *
> -	 * This callback is used to update the display mode of an encoder.
> -	 *
> -	 * Note that the display pipe is completely off when this function is
> -	 * called. Drivers which need hardware to be running before they program
> -	 * the new display mode (because they implement runtime PM) should not
> -	 * use this hook, because the helper library calls it only once and not
> -	 * every time the display pipeline is suspend using either DPMS or the
> -	 * new "ACTIVE" property. Such drivers should instead move all their
> -	 * encoder setup into the @enable callback.
> -	 *
> -	 * This callback is used both by the legacy CRTC helpers and the atomic
> -	 * modeset helpers. It is optional in the atomic helpers.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * If the driver uses the atomic modeset helpers and needs to inspect
> -	 * the connector state or connector display info during mode setting,
> -	 * @atomic_mode_set can be used instead.
> -	 */
> -	void (*mode_set)(struct drm_encoder *encoder,
> -			 struct drm_display_mode *mode,
> -			 struct drm_display_mode *adjusted_mode);
> -
> -	/**
> -	 * @atomic_mode_set:
> -	 *
> -	 * This callback is used to update the display mode of an encoder.
> -	 *
> -	 * Note that the display pipe is completely off when this function is
> -	 * called. Drivers which need hardware to be running before they program
> -	 * the new display mode (because they implement runtime PM) should not
> -	 * use this hook, because the helper library calls it only once and not
> -	 * every time the display pipeline is suspended using either DPMS or the
> -	 * new "ACTIVE" property. Such drivers should instead move all their
> -	 * encoder setup into the @enable callback.
> -	 *
> -	 * This callback is used by the atomic modeset helpers in place of the
> -	 * @mode_set callback, if set by the driver. It is optional and should
> -	 * be used instead of @mode_set if the driver needs to inspect the
> -	 * connector state or display info, since there is no direct way to
> -	 * go from the encoder to the current connector.
> -	 */
> -	void (*atomic_mode_set)(struct drm_encoder *encoder,
> -				struct drm_crtc_state *crtc_state,
> -				struct drm_connector_state *conn_state);
> -
> -	/**
> -	 * @detect:
> -	 *
> -	 * This callback can be used by drivers who want to do detection on the
> -	 * encoder object instead of in connector functions.
> -	 *
> -	 * It is not used by any helper and therefore has purely driver-specific
> -	 * semantics. New drivers shouldn't use this and instead just implement
> -	 * their own private callbacks.
> -	 *
> -	 * FIXME:
> -	 *
> -	 * This should just be converted into a pile of driver vfuncs.
> -	 * Currently radeon, amdgpu and nouveau are using it.
> -	 */
> -	enum drm_connector_status (*detect)(struct drm_encoder *encoder,
> -					    struct drm_connector *connector);
> -
> -	/**
> -	 * @atomic_disable:
> -	 *
> -	 * This callback should be used to disable the encoder. With the atomic
> -	 * drivers it is called before this encoder's CRTC has been shut off
> -	 * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
> -	 * sequence is too simple drivers can just add their own driver private
> -	 * encoder hooks and call them from CRTC's callback by looping over all
> -	 * encoders connected to it using for_each_encoder_on_crtc().
> -	 *
> -	 * This callback is a variant of @disable that provides the atomic state
> -	 * to the driver. If @atomic_disable is implemented, @disable is not
> -	 * called by the helpers.
> -	 *
> -	 * This hook is only used by atomic helpers. Atomic drivers don't need
> -	 * to implement it if there's no need to disable anything at the encoder
> -	 * level. To ensure that runtime PM handling (using either DPMS or the
> -	 * new "ACTIVE" property) works @atomic_disable must be the inverse of
> -	 * @atomic_enable.
> -	 */
> -	void (*atomic_disable)(struct drm_encoder *encoder,
> -			       struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_enable:
> -	 *
> -	 * This callback should be used to enable the encoder. It is called
> -	 * after this encoder's CRTC has been enabled using their own
> -	 * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
> -	 * too simple drivers can just add their own driver private encoder
> -	 * hooks and call them from CRTC's callback by looping over all encoders
> -	 * connected to it using for_each_encoder_on_crtc().
> -	 *
> -	 * This callback is a variant of @enable that provides the atomic state
> -	 * to the driver. If @atomic_enable is implemented, @enable is not
> -	 * called by the helpers.
> -	 *
> -	 * This hook is only used by atomic helpers, it is the opposite of
> -	 * @atomic_disable. Atomic drivers don't need to implement it if there's
> -	 * no need to enable anything at the encoder level. To ensure that
> -	 * runtime PM handling works @atomic_enable must be the inverse of
> -	 * @atomic_disable.
> -	 */
> -	void (*atomic_enable)(struct drm_encoder *encoder,
> -			      struct drm_atomic_state *state);
> -
> -	/**
> -	 * @disable:
> -	 *
> -	 * This callback should be used to disable the encoder. With the atomic
> -	 * drivers it is called before this encoder's CRTC has been shut off
> -	 * using their own &drm_crtc_helper_funcs.disable hook.  If that
> -	 * sequence is too simple drivers can just add their own driver private
> -	 * encoder hooks and call them from CRTC's callback by looping over all
> -	 * encoders connected to it using for_each_encoder_on_crtc().
> -	 *
> -	 * This hook is used both by legacy CRTC helpers and atomic helpers.
> -	 * Atomic drivers don't need to implement it if there's no need to
> -	 * disable anything at the encoder level. To ensure that runtime PM
> -	 * handling (using either DPMS or the new "ACTIVE" property) works
> -	 * @disable must be the inverse of @enable for atomic drivers.
> -	 *
> -	 * For atomic drivers also consider @atomic_disable and save yourself
> -	 * from having to read the NOTE below!
> -	 *
> -	 * NOTE:
> -	 *
> -	 * With legacy CRTC helpers there's a big semantic difference between
> -	 * @disable and other hooks (like @prepare or @dpms) used to shut down a
> -	 * encoder: @disable is only called when also logically disabling the
> -	 * display pipeline and needs to release any resources acquired in
> -	 * @mode_set (like shared PLLs, or again release pinned framebuffers).
> -	 *
> -	 * Therefore @disable must be the inverse of @mode_set plus @commit for
> -	 * drivers still using legacy CRTC helpers, which is different from the
> -	 * rules under atomic.
> -	 */
> -	void (*disable)(struct drm_encoder *encoder);
> -
> -	/**
> -	 * @enable:
> -	 *
> -	 * This callback should be used to enable the encoder. With the atomic
> -	 * drivers it is called after this encoder's CRTC has been enabled using
> -	 * their own &drm_crtc_helper_funcs.enable hook.  If that sequence is
> -	 * too simple drivers can just add their own driver private encoder
> -	 * hooks and call them from CRTC's callback by looping over all encoders
> -	 * connected to it using for_each_encoder_on_crtc().
> -	 *
> -	 * This hook is only used by atomic helpers, it is the opposite of
> -	 * @disable. Atomic drivers don't need to implement it if there's no
> -	 * need to enable anything at the encoder level. To ensure that
> -	 * runtime PM handling (using either DPMS or the new "ACTIVE" property)
> -	 * works @enable must be the inverse of @disable for atomic drivers.
> -	 */
> -	void (*enable)(struct drm_encoder *encoder);
> -
> -	/**
> -	 * @atomic_check:
> -	 *
> -	 * This callback is used to validate encoder state for atomic drivers.
> -	 * Since the encoder is the object connecting the CRTC and connector it
> -	 * gets passed both states, to be able to validate interactions and
> -	 * update the CRTC to match what the encoder needs for the requested
> -	 * connector.
> -	 *
> -	 * Since this provides a strict superset of the functionality of
> -	 * @mode_fixup (the requested and adjusted modes are both available
> -	 * through the passed in &struct drm_crtc_state) @mode_fixup is not
> -	 * called when @atomic_check is implemented.
> -	 *
> -	 * This function is used by the atomic helpers, but it is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of an atomic update. The
> -	 * driver is not allowed to change anything outside of the free-standing
> -	 * state objects passed-in or assembled in the overall &drm_atomic_state
> -	 * update tracking structure.
> -	 *
> -	 * Also beware that userspace can request its own custom modes, neither
> -	 * core nor helpers filter modes to the list of probe modes reported by
> -	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
> -	 * that modes are filtered consistently put any encoder constraints and
> -	 * limits checks into @mode_valid.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success, -EINVAL if the state or the transition can't be
> -	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> -	 * attempt to obtain another state object ran into a &drm_modeset_lock
> -	 * deadlock.
> -	 */
> -	int (*atomic_check)(struct drm_encoder *encoder,
> -			    struct drm_crtc_state *crtc_state,
> -			    struct drm_connector_state *conn_state);
> -};
> -
> -/**
> - * drm_encoder_helper_add - sets the helper vtable for an encoder
> - * @encoder: DRM encoder
> - * @funcs: helper vtable to set for @encoder
> - */
> -static inline void drm_encoder_helper_add(struct drm_encoder *encoder,
> -					  const struct drm_encoder_helper_funcs *funcs)
> -{
> -	encoder->helper_private = funcs;
> -}
> -
> -/**
> - * struct drm_connector_helper_funcs - helper operations for connectors
> - *
> - * These functions are used by the atomic and legacy modeset helpers and by the
> - * probe helpers.
> - */
> -struct drm_connector_helper_funcs {
> -	/**
> -	 * @get_modes:
> -	 *
> -	 * This function should fill in all modes currently valid for the sink
> -	 * into the &drm_connector.probed_modes list. It should also update the
> -	 * EDID property by calling drm_connector_update_edid_property().
> -	 *
> -	 * The usual way to implement this is to cache the EDID retrieved in the
> -	 * probe callback somewhere in the driver-private connector structure.
> -	 * In this function drivers then parse the modes in the EDID and add
> -	 * them by calling drm_add_edid_modes(). But connectors that drive a
> -	 * fixed panel can also manually add specific modes using
> -	 * drm_mode_probed_add(). Drivers which manually add modes should also
> -	 * make sure that the &drm_connector.display_info,
> -	 * &drm_connector.width_mm and &drm_connector.height_mm fields are
> -	 * filled in.
> -	 *
> -	 * Note that the caller function will automatically add standard VESA
> -	 * DMT modes up to 1024x768 if the .get_modes() helper operation returns
> -	 * no mode and if the connector status is connector_status_connected or
> -	 * connector_status_unknown. There is no need to call
> -	 * drm_add_modes_noedid() manually in that case.
> -	 *
> -	 * Virtual drivers that just want some standard VESA mode with a given
> -	 * resolution can call drm_add_modes_noedid(), and mark the preferred
> -	 * one using drm_set_preferred_mode().
> -	 *
> -	 * This function is only called after the @detect hook has indicated
> -	 * that a sink is connected and when the EDID isn't overridden through
> -	 * sysfs or the kernel commandline.
> -	 *
> -	 * This callback is used by the probe helpers in e.g.
> -	 * drm_helper_probe_single_connector_modes().
> -	 *
> -	 * To avoid races with concurrent connector state updates, the helper
> -	 * libraries always call this with the &drm_mode_config.connection_mutex
> -	 * held. Because of this it's safe to inspect &drm_connector->state.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * The number of modes added by calling drm_mode_probed_add().
> -	 */
> -	int (*get_modes)(struct drm_connector *connector);
> -
> -	/**
> -	 * @detect_ctx:
> -	 *
> -	 * Check to see if anything is attached to the connector. The parameter
> -	 * force is set to false whilst polling, true when checking the
> -	 * connector due to a user request. force can be used by the driver to
> -	 * avoid expensive, destructive operations during automated probing.
> -	 *
> -	 * This callback is optional, if not implemented the connector will be
> -	 * considered as always being attached.
> -	 *
> -	 * This is the atomic version of &drm_connector_funcs.detect.
> -	 *
> -	 * To avoid races against concurrent connector state updates, the
> -	 * helper libraries always call this with ctx set to a valid context,
> -	 * and &drm_mode_config.connection_mutex will always be locked with
> -	 * the ctx parameter set to this ctx. This allows taking additional
> -	 * locks as required.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * &drm_connector_status indicating the connector's status,
> -	 * or the error code returned by drm_modeset_lock(), -EDEADLK.
> -	 */
> -	int (*detect_ctx)(struct drm_connector *connector,
> -			  struct drm_modeset_acquire_ctx *ctx,
> -			  bool force);
> -
> -	/**
> -	 * @mode_valid:
> -	 *
> -	 * Callback to validate a mode for a connector, irrespective of the
> -	 * specific display configuration.
> -	 *
> -	 * This callback is used by the probe helpers to filter the mode list
> -	 * (which is usually derived from the EDID data block from the sink).
> -	 * See e.g. drm_helper_probe_single_connector_modes().
> -	 *
> -	 * This function is optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This only filters the mode list supplied to userspace in the
> -	 * GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid,
> -	 * &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid,
> -	 * which are also called by the atomic helpers from
> -	 * drm_atomic_helper_check_modeset(). This allows userspace to force and
> -	 * ignore sink constraint (like the pixel clock limits in the screen's
> -	 * EDID), which is useful for e.g. testing, or working around a broken
> -	 * EDID. Any source hardware constraint (which always need to be
> -	 * enforced) therefore should be checked in one of the above callbacks,
> -	 * and not this one here.
> -	 *
> -	 * To avoid races with concurrent connector state updates, the helper
> -	 * libraries always call this with the &drm_mode_config.connection_mutex
> -	 * held. Because of this it's safe to inspect &drm_connector->state.
> -         *
> -	 * RETURNS:
> -	 *
> -	 * Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum
> -	 * drm_mode_status.
> -	 */
> -	enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
> -					   struct drm_display_mode *mode);
> -
> -	/**
> -	 * @mode_valid_ctx:
> -	 *
> -	 * Callback to validate a mode for a connector, irrespective of the
> -	 * specific display configuration.
> -	 *
> -	 * This callback is used by the probe helpers to filter the mode list
> -	 * (which is usually derived from the EDID data block from the sink).
> -	 * See e.g. drm_helper_probe_single_connector_modes().
> -	 *
> -	 * This function is optional, and is the atomic version of
> -	 * &drm_connector_helper_funcs.mode_valid.
> -	 *
> -	 * To allow for accessing the atomic state of modesetting objects, the
> -	 * helper libraries always call this with ctx set to a valid context,
> -	 * and &drm_mode_config.connection_mutex will always be locked with
> -	 * the ctx parameter set to @ctx. This allows for taking additional
> -	 * locks as required.
> -	 *
> -	 * Even though additional locks may be acquired, this callback is
> -	 * still expected not to take any constraints into account which would
> -	 * be influenced by the currently set display state - such constraints
> -	 * should be handled in the driver's atomic check. For example, if a
> -	 * connector shares display bandwidth with other connectors then it
> -	 * would be ok to validate the minimum bandwidth requirement of a mode
> -	 * against the maximum possible bandwidth of the connector. But it
> -	 * wouldn't be ok to take the current bandwidth usage of other
> -	 * connectors into account, as this would change depending on the
> -	 * display state.
> -	 *
> -	 * Returns:
> -	 * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
> -	 * the &enum drm_mode_status value to @status, or a negative error
> -	 * code otherwise.
> -	 *
> -	 */
> -	int (*mode_valid_ctx)(struct drm_connector *connector,
> -			      struct drm_display_mode *mode,
> -			      struct drm_modeset_acquire_ctx *ctx,
> -			      enum drm_mode_status *status);
> -
> -	/**
> -	 * @best_encoder:
> -	 *
> -	 * This function should select the best encoder for the given connector.
> -	 *
> -	 * This function is used by both the atomic helpers (in the
> -	 * drm_atomic_helper_check_modeset() function) and in the legacy CRTC
> -	 * helpers.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * In atomic drivers this function is called in the check phase of an
> -	 * atomic update. The driver is not allowed to change or inspect
> -	 * anything outside of arguments passed-in. Atomic drivers which need to
> -	 * inspect dynamic configuration state should instead use
> -	 * @atomic_best_encoder.
> -	 *
> -	 * You can leave this function to NULL if the connector is only
> -	 * attached to a single encoder. In this case, the core will call
> -	 * drm_connector_get_single_encoder() for you.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * Encoder that should be used for the given connector and connector
> -	 * state, or NULL if no suitable encoder exists. Note that the helpers
> -	 * will ensure that encoders aren't used twice, drivers should not check
> -	 * for this.
> -	 */
> -	struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
> -
> -	/**
> -	 * @atomic_best_encoder:
> -	 *
> -	 * This is the atomic version of @best_encoder for atomic drivers which
> -	 * need to select the best encoder depending upon the desired
> -	 * configuration and can't select it statically.
> -	 *
> -	 * This function is used by drm_atomic_helper_check_modeset().
> -	 * If it is not implemented, the core will fallback to @best_encoder
> -	 * (or drm_connector_get_single_encoder() if @best_encoder is NULL).
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of an atomic update. The
> -	 * driver is not allowed to change anything outside of the
> -	 * &drm_atomic_state update tracking structure passed in.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * Encoder that should be used for the given connector and connector
> -	 * state, or NULL if no suitable encoder exists. Note that the helpers
> -	 * will ensure that encoders aren't used twice, drivers should not check
> -	 * for this.
> -	 */
> -	struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
> -						   struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_check:
> -	 *
> -	 * This hook is used to validate connector state. This function is
> -	 * called from &drm_atomic_helper_check_modeset, and is called when
> -	 * a connector property is set, or a modeset on the crtc is forced.
> -	 *
> -	 * Because &drm_atomic_helper_check_modeset may be called multiple times,
> -	 * this function should handle being called multiple times as well.
> -	 *
> -	 * This function is also allowed to inspect any other object's state and
> -	 * can add more state objects to the atomic commit if needed. Care must
> -	 * be taken though to ensure that state check and compute functions for
> -	 * these added states are all called, and derived state in other objects
> -	 * all updated. Again the recommendation is to just call check helpers
> -	 * until a maximal configuration is reached.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of an atomic update. The
> -	 * driver is not allowed to change anything outside of the free-standing
> -	 * state objects passed-in or assembled in the overall &drm_atomic_state
> -	 * update tracking structure.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success, -EINVAL if the state or the transition can't be
> -	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> -	 * attempt to obtain another state object ran into a &drm_modeset_lock
> -	 * deadlock.
> -	 */
> -	int (*atomic_check)(struct drm_connector *connector,
> -			    struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_commit:
> -	 *
> -	 * This hook is to be used by drivers implementing writeback connectors
> -	 * that need a point when to commit the writeback job to the hardware.
> -	 * The writeback_job to commit is available in the new connector state,
> -	 * in &drm_connector_state.writeback_job.
> -	 *
> -	 * This hook is optional.
> -	 *
> -	 * This callback is used by the atomic modeset helpers.
> -	 */
> -	void (*atomic_commit)(struct drm_connector *connector,
> -			      struct drm_atomic_state *state);
> -
> -	/**
> -	 * @prepare_writeback_job:
> -	 *
> -	 * As writeback jobs contain a framebuffer, drivers may need to
> -	 * prepare and clean them up the same way they can prepare and
> -	 * clean up framebuffers for planes. This optional connector operation
> -	 * is used to support the preparation of writeback jobs. The job
> -	 * prepare operation is called from drm_atomic_helper_prepare_planes()
> -	 * for struct &drm_writeback_connector connectors only.
> -	 *
> -	 * This operation is optional.
> -	 *
> -	 * This callback is used by the atomic modeset helpers.
> -	 */
> -	int (*prepare_writeback_job)(struct drm_writeback_connector *connector,
> -				     struct drm_writeback_job *job);
> -	/**
> -	 * @cleanup_writeback_job:
> -	 *
> -	 * This optional connector operation is used to support the
> -	 * cleanup of writeback jobs. The job cleanup operation is called
> -	 * from the existing drm_writeback_cleanup_job() function, invoked
> -	 * both when destroying the job as part of an aborted commit, or when
> -	 * the job completes.
> -	 *
> -	 * This operation is optional.
> -	 *
> -	 * This callback is used by the atomic modeset helpers.
> -	 */
> -	void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
> -				      struct drm_writeback_job *job);
> -
> -	/**
> -	 * @enable_hpd:
> -	 *
> -	 * Enable hot-plug detection for the connector.
> -	 *
> -	 * This operation is optional.
> -	 *
> -	 * This callback is used by the drm_kms_helper_poll_enable() helpers.
> -	 */
> -	void (*enable_hpd)(struct drm_connector *connector);
> -
> -	/**
> -	 * @disable_hpd:
> -	 *
> -	 * Disable hot-plug detection for the connector.
> -	 *
> -	 * This operation is optional.
> -	 *
> -	 * This callback is used by the drm_kms_helper_poll_disable() helpers.
> -	 */
> -	void (*disable_hpd)(struct drm_connector *connector);
> -};
> -
> -/**
> - * drm_connector_helper_add - sets the helper vtable for a connector
> - * @connector: DRM connector
> - * @funcs: helper vtable to set for @connector
> - */
> -static inline void drm_connector_helper_add(struct drm_connector *connector,
> -					    const struct drm_connector_helper_funcs *funcs)
> -{
> -	connector->helper_private = funcs;
> -}
> -
> -/**
> - * struct drm_plane_helper_funcs - helper operations for planes
> - *
> - * These functions are used by the atomic helpers.
> - */
> -struct drm_plane_helper_funcs {
> -	/**
> -	 * @prepare_fb:
> -	 *
> -	 * This hook is to prepare a framebuffer for scanout by e.g. pinning
> -	 * its backing storage or relocating it into a contiguous block of
> -	 * VRAM. Other possible preparatory work includes flushing caches.
> -	 *
> -	 * This function must not block for outstanding rendering, since it is
> -	 * called in the context of the atomic IOCTL even for async commits to
> -	 * be able to return any errors to userspace. Instead the recommended
> -	 * way is to fill out the &drm_plane_state.fence of the passed-in
> -	 * &drm_plane_state. If the driver doesn't support native fences then
> -	 * equivalent functionality should be implemented through private
> -	 * members in the plane structure.
> -	 *
> -	 * For GEM drivers who neither have a @prepare_fb nor @cleanup_fb hook
> -	 * set drm_gem_plane_helper_prepare_fb() is called automatically to
> -	 * implement this. Other drivers which need additional plane processing
> -	 * can call drm_gem_plane_helper_prepare_fb() from their @prepare_fb
> -	 * hook.
> -	 *
> -	 * The resources acquired in @prepare_fb persist after the end of
> -	 * the atomic commit. Resources that can be release at the commit's end
> -	 * should be acquired in @begin_fb_access and released in @end_fb_access.
> -	 * For example, a GEM buffer's pin operation belongs into @prepare_fb to
> -	 * keep the buffer pinned after the commit. But a vmap operation for
> -	 * shadow-plane helpers belongs into @begin_fb_access, so that atomic
> -	 * helpers remove the mapping at the end of the commit.
> -	 *
> -	 * The helpers will call @cleanup_fb with matching arguments for every
> -	 * successful call to this hook.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional. See @begin_fb_access for preparing per-commit resources.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success or one of the following negative error codes allowed by
> -	 * the &drm_mode_config_funcs.atomic_commit vfunc. When using helpers
> -	 * this callback is the only one which can fail an atomic commit,
> -	 * everything else must complete successfully.
> -	 */
> -	int (*prepare_fb)(struct drm_plane *plane,
> -			  struct drm_plane_state *new_state);
> -	/**
> -	 * @cleanup_fb:
> -	 *
> -	 * This hook is called to clean up any resources allocated for the given
> -	 * framebuffer and plane configuration in @prepare_fb.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional.
> -	 */
> -	void (*cleanup_fb)(struct drm_plane *plane,
> -			   struct drm_plane_state *old_state);
> -
> -	/**
> -	 * @begin_fb_access:
> -	 *
> -	 * This hook prepares the plane for access during an atomic commit.
> -	 * In contrast to @prepare_fb, resources acquired in @begin_fb_access,
> -	 * are released at the end of the atomic commit in @end_fb_access.
> -	 *
> -	 * For example, with shadow-plane helpers, the GEM buffer's vmap
> -	 * operation belongs into @begin_fb_access, so that the buffer's
> -	 * memory will be unmapped at the end of the commit in @end_fb_access.
> -	 * But a GEM buffer's pin operation belongs into @prepare_fb
> -	 * to keep the buffer pinned after the commit.
> -	 *
> -	 * The callback is used by the atomic modeset helpers, but it is optional.
> -	 * See @end_fb_cleanup for undoing the effects of @begin_fb_access and
> -	 * @prepare_fb for acquiring resources until the next pageflip.
> -	 *
> -	 * Returns:
> -	 * 0 on success, or a negative errno code otherwise.
> -	 */
> -	int (*begin_fb_access)(struct drm_plane *plane, struct drm_plane_state *new_plane_state);
> -
> -	/**
> -	 * @end_fb_access:
> -	 *
> -	 * This hook cleans up resources allocated by @begin_fb_access. It it called
> -	 * at the end of a commit for the new plane state.
> -	 */
> -	void (*end_fb_access)(struct drm_plane *plane, struct drm_plane_state *new_plane_state);
> -
> -	/**
> -	 * @atomic_check:
> -	 *
> -	 * Drivers should check plane specific constraints in this hook.
> -	 *
> -	 * When using drm_atomic_helper_check_planes() plane's @atomic_check
> -	 * hooks are called before the ones for CRTCs, which allows drivers to
> -	 * request shared resources that the CRTC controls here. For more
> -	 * complicated dependencies the driver can call the provided check helpers
> -	 * multiple times until the computed state has a final configuration and
> -	 * everything has been checked.
> -	 *
> -	 * This function is also allowed to inspect any other object's state and
> -	 * can add more state objects to the atomic commit if needed. Care must
> -	 * be taken though to ensure that state check and compute functions for
> -	 * these added states are all called, and derived state in other objects
> -	 * all updated. Again the recommendation is to just call check helpers
> -	 * until a maximal configuration is reached.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional.
> -	 *
> -	 * NOTE:
> -	 *
> -	 * This function is called in the check phase of an atomic update. The
> -	 * driver is not allowed to change anything outside of the
> -	 * &drm_atomic_state update tracking structure.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * 0 on success, -EINVAL if the state or the transition can't be
> -	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> -	 * attempt to obtain another state object ran into a &drm_modeset_lock
> -	 * deadlock.
> -	 */
> -	int (*atomic_check)(struct drm_plane *plane,
> -			    struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_update:
> -	 *
> -	 * Drivers should use this function to update the plane state.  This
> -	 * hook is called in-between the &drm_crtc_helper_funcs.atomic_begin and
> -	 * drm_crtc_helper_funcs.atomic_flush callbacks.
> -	 *
> -	 * Note that the power state of the display pipe when this function is
> -	 * called depends upon the exact helpers and calling sequence the driver
> -	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> -	 * the tradeoffs and variants of plane commit helpers.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is optional.
> -	 */
> -	void (*atomic_update)(struct drm_plane *plane,
> -			      struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_enable:
> -	 *
> -	 * Drivers should use this function to unconditionally enable a plane.
> -	 * This hook is called in-between the &drm_crtc_helper_funcs.atomic_begin
> -	 * and drm_crtc_helper_funcs.atomic_flush callbacks. It is called after
> -	 * @atomic_update, which will be called for all enabled planes. Drivers
> -	 * that use @atomic_enable should set up a plane in @atomic_update and
> -	 * afterwards enable the plane in @atomic_enable. If a plane needs to be
> -	 * enabled before installing the scanout buffer, drivers can still do
> -	 * so in @atomic_update.
> -	 *
> -	 * Note that the power state of the display pipe when this function is
> -	 * called depends upon the exact helpers and calling sequence the driver
> -	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> -	 * the tradeoffs and variants of plane commit helpers.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional. If implemented, @atomic_enable should be the inverse of
> -	 * @atomic_disable. Drivers that don't want to use either can still
> -	 * implement the complete plane update in @atomic_update.
> -	 */
> -	void (*atomic_enable)(struct drm_plane *plane,
> -			      struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_disable:
> -	 *
> -	 * Drivers should use this function to unconditionally disable a plane.
> -	 * This hook is called in-between the
> -	 * &drm_crtc_helper_funcs.atomic_begin and
> -	 * drm_crtc_helper_funcs.atomic_flush callbacks. It is an alternative to
> -	 * @atomic_update, which will be called for disabling planes, too, if
> -	 * the @atomic_disable hook isn't implemented.
> -	 *
> -	 * This hook is also useful to disable planes in preparation of a modeset,
> -	 * by calling drm_atomic_helper_disable_planes_on_crtc() from the
> -	 * &drm_crtc_helper_funcs.disable hook.
> -	 *
> -	 * Note that the power state of the display pipe when this function is
> -	 * called depends upon the exact helpers and calling sequence the driver
> -	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> -	 * the tradeoffs and variants of plane commit helpers.
> -	 *
> -	 * This callback is used by the atomic modeset helpers, but it is
> -	 * optional. It's intended to reverse the effects of @atomic_enable.
> -	 */
> -	void (*atomic_disable)(struct drm_plane *plane,
> -			       struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_async_check:
> -	 *
> -	 * Drivers should set this function pointer to check if the plane's
> -	 * atomic state can be updated in a async fashion. Here async means
> -	 * "not vblank synchronized".
> -	 *
> -	 * This hook is called by drm_atomic_async_check() to establish if a
> -	 * given update can be committed asynchronously, that is, if it can
> -	 * jump ahead of the state currently queued for update.
> -	 *
> -	 * RETURNS:
> -	 *
> -	 * Return 0 on success and any error returned indicates that the update
> -	 * can not be applied in asynchronous manner.
> -	 */
> -	int (*atomic_async_check)(struct drm_plane *plane,
> -				  struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_async_update:
> -	 *
> -	 * Drivers should set this function pointer to perform asynchronous
> -	 * updates of planes, that is, jump ahead of the currently queued
> -	 * state and update the plane. Here async means "not vblank
> -	 * synchronized".
> -	 *
> -	 * This hook is called by drm_atomic_helper_async_commit().
> -	 *
> -	 * An async update will happen on legacy cursor updates. An async
> -	 * update won't happen if there is an outstanding commit modifying
> -	 * the same plane.
> -	 *
> -	 * When doing async_update drivers shouldn't replace the
> -	 * &drm_plane_state but update the current one with the new plane
> -	 * configurations in the new plane_state.
> -	 *
> -	 * Drivers should also swap the framebuffers between current plane
> -	 * state (&drm_plane.state) and new_state.
> -	 * This is required since cleanup for async commits is performed on
> -	 * the new state, rather than old state like for traditional commits.
> -	 * Since we want to give up the reference on the current (old) fb
> -	 * instead of our brand new one, swap them in the driver during the
> -	 * async commit.
> -	 *
> -	 * FIXME:
> -	 *  - It only works for single plane updates
> -	 *  - Async Pageflips are not supported yet
> -	 *  - Some hw might still scan out the old buffer until the next
> -	 *    vblank, however we let go of the fb references as soon as
> -	 *    we run this hook. For now drivers must implement their own workers
> -	 *    for deferring if needed, until a common solution is created.
> -	 */
> -	void (*atomic_async_update)(struct drm_plane *plane,
> -				    struct drm_atomic_state *state);
> -};
> -
> -/**
> - * drm_plane_helper_add - sets the helper vtable for a plane
> - * @plane: DRM plane
> - * @funcs: helper vtable to set for @plane
> - */
> -static inline void drm_plane_helper_add(struct drm_plane *plane,
> -					const struct drm_plane_helper_funcs *funcs)
> -{
> -	plane->helper_private = funcs;
> -}
> -
> -/**
> - * struct drm_mode_config_helper_funcs - global modeset helper operations
> - *
> - * These helper functions are used by the atomic helpers.
> - */
> -struct drm_mode_config_helper_funcs {
> -	/**
> -	 * @atomic_commit_tail:
> -	 *
> -	 * This hook is used by the default atomic_commit() hook implemented in
> -	 * drm_atomic_helper_commit() together with the nonblocking commit
> -	 * helpers (see drm_atomic_helper_setup_commit() for a starting point)
> -	 * to implement blocking and nonblocking commits easily. It is not used
> -	 * by the atomic helpers
> -	 *
> -	 * This function is called when the new atomic state has already been
> -	 * swapped into the various state pointers. The passed in state
> -	 * therefore contains copies of the old/previous state. This hook should
> -	 * commit the new state into hardware. Note that the helpers have
> -	 * already waited for preceding atomic commits and fences, but drivers
> -	 * can add more waiting calls at the start of their implementation, e.g.
> -	 * to wait for driver-internal request for implicit syncing, before
> -	 * starting to commit the update to the hardware.
> -	 *
> -	 * After the atomic update is committed to the hardware this hook needs
> -	 * to call drm_atomic_helper_commit_hw_done(). Then wait for the update
> -	 * to be executed by the hardware, for example using
> -	 * drm_atomic_helper_wait_for_vblanks() or
> -	 * drm_atomic_helper_wait_for_flip_done(), and then clean up the old
> -	 * framebuffers using drm_atomic_helper_cleanup_planes().
> -	 *
> -	 * When disabling a CRTC this hook _must_ stall for the commit to
> -	 * complete. Vblank waits don't work on disabled CRTC, hence the core
> -	 * can't take care of this. And it also can't rely on the vblank event,
> -	 * since that can be signalled already when the screen shows black,
> -	 * which can happen much earlier than the last hardware access needed to
> -	 * shut off the display pipeline completely.
> -	 *
> -	 * This hook is optional, the default implementation is
> -	 * drm_atomic_helper_commit_tail().
> -	 */
> -	void (*atomic_commit_tail)(struct drm_atomic_state *state);
> -
> -	/**
> -	 * @atomic_commit_setup:
> -	 *
> -	 * This hook is used by the default atomic_commit() hook implemented in
> -	 * drm_atomic_helper_commit() together with the nonblocking helpers (see
> -	 * drm_atomic_helper_setup_commit()) to extend the DRM commit setup. It
> -	 * is not used by the atomic helpers.
> -	 *
> -	 * This function is called at the end of
> -	 * drm_atomic_helper_setup_commit(), so once the commit has been
> -	 * properly setup across the generic DRM object states. It allows
> -	 * drivers to do some additional commit tracking that isn't related to a
> -	 * CRTC, plane or connector, tracked in a &drm_private_obj structure.
> -	 *
> -	 * Note that the documentation of &drm_private_obj has more details on
> -	 * how one should implement this.
> -	 *
> -	 * This hook is optional.
> -	 */
> -	int (*atomic_commit_setup)(struct drm_atomic_state *state);
> -};
> +#include <drm/drm_crtc_helper_vtable.h>
> +#include <drm/drm_encoder_helper_vtable.h>
> +#include <drm/drm_connector_helper_vtable.h>
> +#include <drm/drm_plane_helper_vtable.h>
> +#include <drm/drm_mode_config_helper_vtable.h>
>   
>   #endif
> diff --git a/include/drm/drm_plane_helper_vtable.h b/include/drm/drm_plane_helper_vtable.h
> new file mode 100644
> index 0000000000000000..e735aa9733869383
> --- /dev/null
> +++ b/include/drm/drm_plane_helper_vtable.h
> @@ -0,0 +1,297 @@
> +/*
> + * Copyright © 2006 Keith Packard
> + * Copyright © 2007-2008 Dave Airlie
> + * Copyright © 2007-2008 Intel Corporation
> + *   Jesse Barnes <jesse.barnes@...el.com>
> + * Copyright © 2011-2013 Intel Corporation
> + * Copyright © 2015 Intel Corporation
> + *   Daniel Vetter <daniel.vetter@...ll.ch>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __DRM_PLANE_HELPER_VTABLE_H__
> +#define __DRM_PLANE_HELPER_VTABLE_H__
> +
> +/**
> + * struct drm_plane_helper_funcs - helper operations for planes
> + *
> + * These functions are used by the atomic helpers.
> + */
> +struct drm_plane_helper_funcs {
> +	/**
> +	 * @prepare_fb:
> +	 *
> +	 * This hook is to prepare a framebuffer for scanout by e.g. pinning
> +	 * its backing storage or relocating it into a contiguous block of
> +	 * VRAM. Other possible preparatory work includes flushing caches.
> +	 *
> +	 * This function must not block for outstanding rendering, since it is
> +	 * called in the context of the atomic IOCTL even for async commits to
> +	 * be able to return any errors to userspace. Instead the recommended
> +	 * way is to fill out the &drm_plane_state.fence of the passed-in
> +	 * &drm_plane_state. If the driver doesn't support native fences then
> +	 * equivalent functionality should be implemented through private
> +	 * members in the plane structure.
> +	 *
> +	 * For GEM drivers who neither have a @prepare_fb nor @cleanup_fb hook
> +	 * set drm_gem_plane_helper_prepare_fb() is called automatically to
> +	 * implement this. Other drivers which need additional plane processing
> +	 * can call drm_gem_plane_helper_prepare_fb() from their @prepare_fb
> +	 * hook.
> +	 *
> +	 * The resources acquired in @prepare_fb persist after the end of
> +	 * the atomic commit. Resources that can be release at the commit's end
> +	 * should be acquired in @begin_fb_access and released in @end_fb_access.
> +	 * For example, a GEM buffer's pin operation belongs into @prepare_fb to
> +	 * keep the buffer pinned after the commit. But a vmap operation for
> +	 * shadow-plane helpers belongs into @begin_fb_access, so that atomic
> +	 * helpers remove the mapping at the end of the commit.
> +	 *
> +	 * The helpers will call @cleanup_fb with matching arguments for every
> +	 * successful call to this hook.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional. See @begin_fb_access for preparing per-commit resources.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success or one of the following negative error codes allowed by
> +	 * the &drm_mode_config_funcs.atomic_commit vfunc. When using helpers
> +	 * this callback is the only one which can fail an atomic commit,
> +	 * everything else must complete successfully.
> +	 */
> +	int (*prepare_fb)(struct drm_plane *plane,
> +			  struct drm_plane_state *new_state);
> +	/**
> +	 * @cleanup_fb:
> +	 *
> +	 * This hook is called to clean up any resources allocated for the given
> +	 * framebuffer and plane configuration in @prepare_fb.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional.
> +	 */
> +	void (*cleanup_fb)(struct drm_plane *plane,
> +			   struct drm_plane_state *old_state);
> +
> +	/**
> +	 * @begin_fb_access:
> +	 *
> +	 * This hook prepares the plane for access during an atomic commit.
> +	 * In contrast to @prepare_fb, resources acquired in @begin_fb_access,
> +	 * are released at the end of the atomic commit in @end_fb_access.
> +	 *
> +	 * For example, with shadow-plane helpers, the GEM buffer's vmap
> +	 * operation belongs into @begin_fb_access, so that the buffer's
> +	 * memory will be unmapped at the end of the commit in @end_fb_access.
> +	 * But a GEM buffer's pin operation belongs into @prepare_fb
> +	 * to keep the buffer pinned after the commit.
> +	 *
> +	 * The callback is used by the atomic modeset helpers, but it is optional.
> +	 * See @end_fb_cleanup for undoing the effects of @begin_fb_access and
> +	 * @prepare_fb for acquiring resources until the next pageflip.
> +	 *
> +	 * Returns:
> +	 * 0 on success, or a negative errno code otherwise.
> +	 */
> +	int (*begin_fb_access)(struct drm_plane *plane, struct drm_plane_state *new_plane_state);
> +
> +	/**
> +	 * @end_fb_access:
> +	 *
> +	 * This hook cleans up resources allocated by @begin_fb_access. It it called
> +	 * at the end of a commit for the new plane state.
> +	 */
> +	void (*end_fb_access)(struct drm_plane *plane, struct drm_plane_state *new_plane_state);
> +
> +	/**
> +	 * @atomic_check:
> +	 *
> +	 * Drivers should check plane specific constraints in this hook.
> +	 *
> +	 * When using drm_atomic_helper_check_planes() plane's @atomic_check
> +	 * hooks are called before the ones for CRTCs, which allows drivers to
> +	 * request shared resources that the CRTC controls here. For more
> +	 * complicated dependencies the driver can call the provided check helpers
> +	 * multiple times until the computed state has a final configuration and
> +	 * everything has been checked.
> +	 *
> +	 * This function is also allowed to inspect any other object's state and
> +	 * can add more state objects to the atomic commit if needed. Care must
> +	 * be taken though to ensure that state check and compute functions for
> +	 * these added states are all called, and derived state in other objects
> +	 * all updated. Again the recommendation is to just call check helpers
> +	 * until a maximal configuration is reached.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional.
> +	 *
> +	 * NOTE:
> +	 *
> +	 * This function is called in the check phase of an atomic update. The
> +	 * driver is not allowed to change anything outside of the
> +	 * &drm_atomic_state update tracking structure.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * 0 on success, -EINVAL if the state or the transition can't be
> +	 * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> +	 * attempt to obtain another state object ran into a &drm_modeset_lock
> +	 * deadlock.
> +	 */
> +	int (*atomic_check)(struct drm_plane *plane,
> +			    struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_update:
> +	 *
> +	 * Drivers should use this function to update the plane state.  This
> +	 * hook is called in-between the &drm_crtc_helper_funcs.atomic_begin and
> +	 * drm_crtc_helper_funcs.atomic_flush callbacks.
> +	 *
> +	 * Note that the power state of the display pipe when this function is
> +	 * called depends upon the exact helpers and calling sequence the driver
> +	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> +	 * the tradeoffs and variants of plane commit helpers.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is optional.
> +	 */
> +	void (*atomic_update)(struct drm_plane *plane,
> +			      struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_enable:
> +	 *
> +	 * Drivers should use this function to unconditionally enable a plane.
> +	 * This hook is called in-between the &drm_crtc_helper_funcs.atomic_begin
> +	 * and drm_crtc_helper_funcs.atomic_flush callbacks. It is called after
> +	 * @atomic_update, which will be called for all enabled planes. Drivers
> +	 * that use @atomic_enable should set up a plane in @atomic_update and
> +	 * afterwards enable the plane in @atomic_enable. If a plane needs to be
> +	 * enabled before installing the scanout buffer, drivers can still do
> +	 * so in @atomic_update.
> +	 *
> +	 * Note that the power state of the display pipe when this function is
> +	 * called depends upon the exact helpers and calling sequence the driver
> +	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> +	 * the tradeoffs and variants of plane commit helpers.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional. If implemented, @atomic_enable should be the inverse of
> +	 * @atomic_disable. Drivers that don't want to use either can still
> +	 * implement the complete plane update in @atomic_update.
> +	 */
> +	void (*atomic_enable)(struct drm_plane *plane,
> +			      struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_disable:
> +	 *
> +	 * Drivers should use this function to unconditionally disable a plane.
> +	 * This hook is called in-between the
> +	 * &drm_crtc_helper_funcs.atomic_begin and
> +	 * drm_crtc_helper_funcs.atomic_flush callbacks. It is an alternative to
> +	 * @atomic_update, which will be called for disabling planes, too, if
> +	 * the @atomic_disable hook isn't implemented.
> +	 *
> +	 * This hook is also useful to disable planes in preparation of a modeset,
> +	 * by calling drm_atomic_helper_disable_planes_on_crtc() from the
> +	 * &drm_crtc_helper_funcs.disable hook.
> +	 *
> +	 * Note that the power state of the display pipe when this function is
> +	 * called depends upon the exact helpers and calling sequence the driver
> +	 * has picked. See drm_atomic_helper_commit_planes() for a discussion of
> +	 * the tradeoffs and variants of plane commit helpers.
> +	 *
> +	 * This callback is used by the atomic modeset helpers, but it is
> +	 * optional. It's intended to reverse the effects of @atomic_enable.
> +	 */
> +	void (*atomic_disable)(struct drm_plane *plane,
> +			       struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_async_check:
> +	 *
> +	 * Drivers should set this function pointer to check if the plane's
> +	 * atomic state can be updated in a async fashion. Here async means
> +	 * "not vblank synchronized".
> +	 *
> +	 * This hook is called by drm_atomic_async_check() to establish if a
> +	 * given update can be committed asynchronously, that is, if it can
> +	 * jump ahead of the state currently queued for update.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * Return 0 on success and any error returned indicates that the update
> +	 * can not be applied in asynchronous manner.
> +	 */
> +	int (*atomic_async_check)(struct drm_plane *plane,
> +				  struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_async_update:
> +	 *
> +	 * Drivers should set this function pointer to perform asynchronous
> +	 * updates of planes, that is, jump ahead of the currently queued
> +	 * state and update the plane. Here async means "not vblank
> +	 * synchronized".
> +	 *
> +	 * This hook is called by drm_atomic_helper_async_commit().
> +	 *
> +	 * An async update will happen on legacy cursor updates. An async
> +	 * update won't happen if there is an outstanding commit modifying
> +	 * the same plane.
> +	 *
> +	 * When doing async_update drivers shouldn't replace the
> +	 * &drm_plane_state but update the current one with the new plane
> +	 * configurations in the new plane_state.
> +	 *
> +	 * Drivers should also swap the framebuffers between current plane
> +	 * state (&drm_plane.state) and new_state.
> +	 * This is required since cleanup for async commits is performed on
> +	 * the new state, rather than old state like for traditional commits.
> +	 * Since we want to give up the reference on the current (old) fb
> +	 * instead of our brand new one, swap them in the driver during the
> +	 * async commit.
> +	 *
> +	 * FIXME:
> +	 *  - It only works for single plane updates
> +	 *  - Async Pageflips are not supported yet
> +	 *  - Some hw might still scan out the old buffer until the next
> +	 *    vblank, however we let go of the fb references as soon as
> +	 *    we run this hook. For now drivers must implement their own workers
> +	 *    for deferring if needed, until a common solution is created.
> +	 */
> +	void (*atomic_async_update)(struct drm_plane *plane,
> +				    struct drm_atomic_state *state);
> +};
> +
> +/**
> + * drm_plane_helper_add - sets the helper vtable for a plane
> + * @plane: DRM plane
> + * @funcs: helper vtable to set for @plane
> + */
> +static inline void drm_plane_helper_add(struct drm_plane *plane,
> +					const struct drm_plane_helper_funcs *funcs)
> +{
> +	plane->helper_private = funcs;
> +}
> +
> +#endif /* __DRM_PLANE_HELPER_VTABLE_H__ */

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (841 bytes)

Powered by blists - more mailing lists