linux-kernel - Re: [PATCH 07/29] drm/atomic: Implement drm_atomic_print_old

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Message-ID: <42e891ee-87b8-448e-a0c7-4f3e3b790556@suse.de>
Date: Tue, 2 Sep 2025 15:26:49 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Maxime Ripard <mripard@...nel.org>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...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>,
 Jyri Sarha <jyri.sarha@....fi>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Devarsh Thakkar <devarsht@...com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/29] drm/atomic: Implement drm_atomic_print_old_state



Am 02.09.25 um 10:32 schrieb Maxime Ripard:
> We currently have a helper to print the new states associated to a
> drm_atomic_state, but we don't have a variant to print the old state.
>
> It's somewhat expected, since we almost never care about what the new
> state looks like when we commit a new state, but we're about to change
> that.
>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

I assume something later in the series uses this code?

> ---
>   drivers/gpu/drm/drm_atomic.c        | 45 +++++++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/drm_crtc_internal.h |  2 ++
>   2 files changed, 47 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 9b198610791d19c7fd276ca59264a961d21caf43..38f2b2633fa992b3543e8c425c7faeab1ce69765 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1875,10 +1875,55 @@ void drm_atomic_print_new_state(const struct drm_atomic_state *state,
>   	for_each_new_private_obj_in_state(state, obj, obj_state, i)
>   		drm_atomic_private_obj_print_state(p, obj_state);
>   }
>   EXPORT_SYMBOL(drm_atomic_print_new_state);
>   
> +/**
> + * drm_atomic_print_old_state - prints drm atomic state
> + * @state: atomic configuration to check
> + * @p: drm printer
> + *
> + * This functions prints the drm atomic state snapshot using the drm printer
> + * which is passed to it. This snapshot can be used for debugging purposes.
> + *
> + * Note that this function looks into the old state objects and hence its not
> + * safe to be used after the call to drm_atomic_helper_commit_hw_done().
> + */
> +void drm_atomic_print_old_state(const struct drm_atomic_state *state,
> +		struct drm_printer *p)
> +{
> +	struct drm_plane *plane;
> +	struct drm_plane_state *plane_state;
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_connector *connector;
> +	struct drm_connector_state *connector_state;
> +	struct drm_private_obj *obj;
> +	struct drm_private_state *obj_state;
> +	int i;
> +
> +	if (!p) {
> +		drm_err(state->dev, "invalid drm printer\n");
> +		return;
> +	}
> +
> +	drm_dbg_atomic(state->dev, "checking %p\n", state);
> +
> +	for_each_old_plane_in_state(state, plane, plane_state, i)
> +		drm_atomic_plane_print_state(p, plane_state);
> +
> +	for_each_old_crtc_in_state(state, crtc, crtc_state, i)
> +		drm_atomic_crtc_print_state(p, crtc_state);
> +
> +	for_each_old_connector_in_state(state, connector, connector_state, i)
> +		drm_atomic_connector_print_state(p, connector_state);
> +
> +	for_each_old_private_obj_in_state(state, obj, obj_state, i)
> +		drm_atomic_private_obj_print_state(p, obj_state);
> +}
> +EXPORT_SYMBOL(drm_atomic_print_old_state);
> +
>   static void __drm_state_dump(struct drm_device *dev, struct drm_printer *p,
>   			     bool take_locks)
>   {
>   	struct drm_mode_config *config = &dev->mode_config;
>   	struct drm_plane *plane;
> diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
> index 89706aa8232fc0b2830af67c7588985a29653299..a8139fda1a1015c2ac8d8af3b12c5ac0b00cfc1a 100644
> --- a/drivers/gpu/drm/drm_crtc_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_internal.h
> @@ -249,10 +249,12 @@ int __drm_atomic_helper_disable_plane(struct drm_plane *plane,
>   int __drm_atomic_helper_set_config(struct drm_mode_set *set,
>   				   struct drm_atomic_state *state);
>   
>   void drm_atomic_print_new_state(const struct drm_atomic_state *state,
>   		struct drm_printer *p);
> +void drm_atomic_print_old_state(const struct drm_atomic_state *state,
> +				struct drm_printer *p);
>   
>   /* drm_atomic_uapi.c */
>   int drm_atomic_connector_commit_dpms(struct drm_atomic_state *state,
>   				     struct drm_connector *connector,
>   				     int mode);
>

-- 
--
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)