[PATCH 03/28] drm/writeback: Define function to get drm_connector from writeback

[Dmitry Baryshkov]

On Fri, Jul 25, 2025 at 10:33:44AM +0530, Suraj Kandpal wrote:
> Now that drm_connector may not always be embedded within
> drm_writeback_connector, let's define a function which either uses
> the writeback helper hook that returns the drm_connector associated
> with the drm_writeback_connector or just return the drm_connector
> embedded inside drm_writeback_connector if the helper hook is not
> present. Lets use this function and call it whenever
> drm_connector is required mostly when connector helper private funcs
> need to be fetched.
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/drm_writeback.c | 33 ++++++++++++++++++++++++++-------
>  1 file changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> index e9f7123270d6..d610cb827975 100644
> --- a/drivers/gpu/drm/drm_writeback.c
> +++ b/drivers/gpu/drm/drm_writeback.c
> @@ -120,6 +120,18 @@ drm_connector_to_writeback(struct drm_connector *connector)
>  }
>  EXPORT_SYMBOL(drm_connector_to_writeback);
>  
> +static struct drm_connector *
> +drm_connector_from_writeback(struct drm_writeback_connector *wb_connector)
> +{
> +	const struct drm_writeback_connector_helper_funcs *funcs =
> +		wb_connector->helper_private;
> +
> +	if (funcs && funcs->get_connector_from_writeback)
> +		return funcs->get_connector_from_writeback(wb_connector);

The get_connector_from_writeback() and
drm_writeback_connector_helper_funcs should be moved to this patch.

However it feels really awkward to make drm_writeback_connector, which
is a wrapper around the drm_connector, to use some external DRM
connector. A quick grepping reveals API (which you missed) that expects
drm_writeback_connector.base to be a valid connector. And it would be
very hard to catch sunch an API later on.

If you want to use DRM framwework, while retaining
intel_connector for writeback connectors, I'd suggest following slightly
different path: extract common parts of drm_writeback_connector into a
common structure, and use it within the DRM core. Then provide functions
to fetch drm_connector from that struct or fetch it from drm_connector.


> +
> +	return &wb_connector->base;
> +}
> +
>  static int create_writeback_properties(struct drm_device *dev)
>  {
>  	struct drm_property *prop;
> @@ -478,6 +490,7 @@ drm_writeback_connector_init_with_conn(struct drm_device *dev, struct drm_connec
>  	if (ret)
>  		goto connector_fail;
>  
> +	drm_writeback_connector_helper_add(wb_connector, wb_funcs);
>  	INIT_LIST_HEAD(&wb_connector->job_queue);
>  	spin_lock_init(&wb_connector->job_lock);
>  
> @@ -527,13 +540,15 @@ int drm_writeback_set_fb(struct drm_connector_state *conn_state,
>  
>  int drm_writeback_prepare_job(struct drm_writeback_job *job)
>  {
> -	struct drm_writeback_connector *connector = job->connector;
> +	struct drm_writeback_connector *wb_connector = job->connector;
> +	struct drm_connector *connector =
> +		drm_connector_from_writeback(wb_connector);
>  	const struct drm_connector_helper_funcs *funcs =
> -		connector->base.helper_private;
> +		connector->helper_private;
>  	int ret;
>  
>  	if (funcs->prepare_writeback_job) {
> -		ret = funcs->prepare_writeback_job(connector, job);
> +		ret = funcs->prepare_writeback_job(wb_connector, job);
>  		if (ret < 0)
>  			return ret;
>  	}
> @@ -579,12 +594,14 @@ EXPORT_SYMBOL(drm_writeback_queue_job);
>  
>  void drm_writeback_cleanup_job(struct drm_writeback_job *job)
>  {
> -	struct drm_writeback_connector *connector = job->connector;
> +	struct drm_writeback_connector *wb_connector = job->connector;
> +	struct drm_connector *connector =
> +		drm_connector_from_writeback(wb_connector);
>  	const struct drm_connector_helper_funcs *funcs =
> -		connector->base.helper_private;
> +		connector->helper_private;
>  
>  	if (job->prepared && funcs->cleanup_writeback_job)
> -		funcs->cleanup_writeback_job(connector, job);
> +		funcs->cleanup_writeback_job(wb_connector, job);
>  
>  	if (job->fb)
>  		drm_framebuffer_put(job->fb);
> @@ -665,9 +682,11 @@ EXPORT_SYMBOL(drm_writeback_signal_completion);
>  struct dma_fence *
>  drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
>  {
> +	struct drm_connector *connector =
> +		drm_connector_from_writeback(wb_connector);
>  	struct dma_fence *fence;
>  
> -	if (WARN_ON(wb_connector->base.connector_type !=
> +	if (WARN_ON(connector->connector_type !=
>  		    DRM_MODE_CONNECTOR_WRITEBACK))
>  		return NULL;
>  
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry