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Message-ID: <Z8nC7JcaK2Vqs_LP@phenom.ffwll.local>
Date: Thu, 6 Mar 2025 16:44:44 +0100
From: Simona Vetter <simona.vetter@...ll.ch>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Thomas Zimmermann <tzimmermann@...e.de>,
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>,
Douglas Anderson <dianders@...omium.org>,
Herve Codina <herve.codina@...tlin.com>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Simona Vetter <simona.vetter@...ll.ch>
Subject: Re: [PATCH v5 04/16] drm/atomic: Introduce helper to lookup
connector by encoder
On Tue, Mar 04, 2025 at 12:10:47PM +0100, Maxime Ripard wrote:
> With the bridges switching over to drm_bridge_connector, the direct
> association between a bridge driver and its connector was lost.
>
> This is mitigated for atomic bridge drivers by the fact you can access
> the encoder, and then call drm_atomic_get_old_connector_for_encoder() or
> drm_atomic_get_new_connector_for_encoder() with drm_atomic_state.
>
> This was also made easier by providing drm_atomic_state directly to all
> atomic hooks bridges can implement.
>
> However, bridge drivers don't have a way to access drm_atomic_state
> outside of the modeset path, like from the hotplug interrupt path or any
> interrupt handler.
>
> Let's introduce a function to retrieve the connector currently assigned
> to an encoder, without using drm_atomic_state, to make these drivers'
> life easier.
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Co-developed-by: Simona Vetter <simona.vetter@...ll.ch>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
> drivers/gpu/drm/drm_atomic.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_atomic.h | 3 +++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 9ea2611770f43ce7ccba410406d5f2c528aab022..b926b132590e78f8d41d48eb4da4bccf170ee236 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -985,10 +985,55 @@ drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
>
> return NULL;
> }
> EXPORT_SYMBOL(drm_atomic_get_new_connector_for_encoder);
>
> +/**
> + * drm_atomic_get_connector_for_encoder - Get connector currently assigned to an encoder
> + * @encoder: The encoder to find the connector of
> + * @ctx: Modeset locking context
> + *
> + * This function finds and returns the connector currently assigned to
> + * an @encoder.
I think it'd be good to link to the other atomic connector functions like
drm_atomic_get_old/new_connector_for_encoder and explain when to use them.
So also add links to the kerneldoc of these other functions pointing to
here.
- This function is for detect, link repair or anything else that comes
from the hardware. Or in general, anything that's not in atomic
commit/check code paths.
- In atomic check/commit code you want to use the other functions.
Otherwise people will have an even harder time finding the right variant
in this maze of look-alikes :-)
With the kerneldoc suitably polished:
Reviewed-by: Simona Vetter <simona.vetter@...ll.ch>
Signed-off-by: Simona Vetter <simona.vetter@...el.com>
> + *
> + * Returns:
> + * The connector connected to @encoder, or an error pointer otherwise.
> + * When the error is EDEADLK, a deadlock has been detected and the
> + * sequence must be restarted.
> + */
> +struct drm_connector *
> +drm_atomic_get_connector_for_encoder(const struct drm_encoder *encoder,
> + struct drm_modeset_acquire_ctx *ctx)
> +{
> + struct drm_connector_list_iter conn_iter;
> + struct drm_connector *out_connector = ERR_PTR(-EINVAL);
> + struct drm_connector *connector;
> + struct drm_device *dev = encoder->dev;
> + int ret;
> +
> + ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
> + if (ret)
> + return ERR_PTR(ret);
> +
> + drm_connector_list_iter_begin(dev, &conn_iter);
> + drm_for_each_connector_iter(connector, &conn_iter) {
> + if (!connector->state)
> + continue;
> +
> + if (encoder == connector->state->best_encoder) {
> + out_connector = connector;
> + break;
> + }
> + }
> + drm_connector_list_iter_end(&conn_iter);
> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> + return out_connector;
> +}
> +EXPORT_SYMBOL(drm_atomic_get_connector_for_encoder);
> +
> +
> /**
> * drm_atomic_get_old_crtc_for_encoder - Get old crtc for an encoder
> * @state: Atomic state
> * @encoder: The encoder to fetch the crtc state for
> *
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 4c673f0698fef6b60f77db980378d5e88e0e250e..38636a593c9d98cadda85ccd67326cb152f0dd27 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -623,10 +623,13 @@ struct drm_connector *
> drm_atomic_get_old_connector_for_encoder(const struct drm_atomic_state *state,
> struct drm_encoder *encoder);
> struct drm_connector *
> drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
> struct drm_encoder *encoder);
> +struct drm_connector *
> +drm_atomic_get_connector_for_encoder(const struct drm_encoder *encoder,
> + struct drm_modeset_acquire_ctx *ctx);
>
> struct drm_crtc *
> drm_atomic_get_old_crtc_for_encoder(struct drm_atomic_state *state,
> struct drm_encoder *encoder);
> struct drm_crtc *
>
> --
> 2.48.1
>
--
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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