On Mon, Aug 11, 2025 at 02:57:00PM +0530, Suraj Kandpal wrote:
> Some drivers cannot work with the current design where the connector
> is embedded within the drm_writeback_connector such as intel and
> some drivers that can get it working end up adding a lot of checks
> all around the code to check if it's a writeback conenctor or not.
> To solve this we move the drm_writeback_connector within the
> drm_connector and remove the drm_connector base which was in
> drm_writeback_connector. We do all other required
> modifications that come with these changes along with addition
> of new function which returns the drm_connector when
> drm_writeback_connector is present.
> All drivers will be expected to allocate the drm_connector.
>
> Signed-off-by: Suraj Kandpal <suraj.kand...@intel.com>
> ---
> drivers/gpu/drm/drm_writeback.c | 33 ++++++++++------
> include/drm/drm_connector.h | 60 +++++++++++++++++++++++++++++
> include/drm/drm_writeback.h | 68 ++++-----------------------------
> 3 files changed, 89 insertions(+), 72 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> index ec2575c4c21b..198b8c488056 100644
> --- a/drivers/gpu/drm/drm_writeback.c
> +++ b/drivers/gpu/drm/drm_writeback.c
> @@ -89,8 +89,10 @@ static const char
> *drm_writeback_fence_get_driver_name(struct dma_fence *fence)
> {
> struct drm_writeback_connector *wb_connector =
> fence_to_wb_connector(fence);
> + struct drm_connector *connector =
> + drm_writeback_to_connector(wb_connector);
>
> - return wb_connector->base.dev->driver->name;
> + return connector->dev->driver->name;
> }
>
> static const char *
> @@ -187,7 +189,8 @@ static int __drm_writeback_connector_init(struct
> drm_device *dev,
> struct drm_encoder *enc, const u32
> *formats,
> int n_formats)
> {
> - struct drm_connector *connector = &wb_connector->base;
> + struct drm_connector *connector =
> + drm_writeback_to_connector(wb_connector);
> struct drm_mode_config *config = &dev->mode_config;
> struct drm_property_blob *blob;
> int ret = create_writeback_properties(dev);
> @@ -269,7 +272,8 @@ int drm_writeback_connector_init(struct drm_device *dev,
> struct drm_encoder *enc,
> const u32 *formats, int n_formats)
> {
> - struct drm_connector *connector = &wb_connector->base;
> + struct drm_connector *connector =
> + drm_writeback_to_connector(wb_connector);
> int ret;
>
> ret = drm_connector_init(dev, connector, con_funcs,
> @@ -339,7 +343,8 @@ int drmm_writeback_connector_init(struct drm_device *dev,
> struct drm_encoder *enc,
> const u32 *formats, int n_formats)
> {
> - struct drm_connector *connector = &wb_connector->base;
> + struct drm_connector *connector =
> + drm_writeback_to_connector(wb_connector);
> int ret;
>
> ret = drmm_connector_init(dev, connector, con_funcs,
> @@ -382,13 +387,15 @@ 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_writeback_to_connector(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;
> }
> @@ -434,12 +441,14 @@ 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_writeback_to_connector(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);
> @@ -521,8 +530,10 @@ struct dma_fence *
> drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
> {
> struct dma_fence *fence;
> + struct drm_connector *connector =
> + drm_writeback_to_connector(wb_connector);
>
> - if (WARN_ON(wb_connector->base.connector_type !=
> + if (WARN_ON(connector->connector_type !=
> DRM_MODE_CONNECTOR_WRITEBACK))
> return NULL;
>
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 8f34f4b8183d..da63fdafd9f2 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1882,6 +1882,61 @@ struct drm_connector_cec {
> void *data;
> };
>
> +/**
> + * struct drm_writeback_connector - DRM writeback connector
> + */
> +struct drm_writeback_connector {
> + /**
> + * @pixel_formats_blob_ptr:
> + *
> + * DRM blob property data for the pixel formats list on writeback
> + * connectors
> + * See also drm_writeback_connector_init()
> + */
> + struct drm_property_blob *pixel_formats_blob_ptr;
> +
> + /** @job_lock: Protects job_queue */
> + spinlock_t job_lock;
> +
> + /**
> + * @job_queue:
> + *
> + * Holds a list of a connector's writeback jobs; the last item is the
> + * most recent. The first item may be either waiting for the hardware
> + * to begin writing, or currently being written.
> + *
> + * See also: drm_writeback_queue_job() and
> + * drm_writeback_signal_completion()
> + */
> + struct list_head job_queue;
> +
> + /**
> + * @fence_context:
> + *
> + * timeline context used for fence operations.
> + */
> + unsigned int fence_context;
> + /**
> + * @fence_lock:
> + *
> + * spinlock to protect the fences in the fence_context.
> + */
> + spinlock_t fence_lock;
> + /**
> + * @fence_seqno:
> + *
> + * Seqno variable used as monotonic counter for the fences
> + * created on the connector's timeline.
> + */
> + unsigned long fence_seqno;
> + /**
> + * @timeline_name:
> + *
> + * The name of the connector's fence timeline.
> + */
> + char timeline_name[32];
> +};
> +
> /**
> * struct drm_connector - central DRM connector control structure
> *
> @@ -2305,6 +2360,11 @@ struct drm_connector {
> * @cec: CEC-related data.
> */
> struct drm_connector_cec cec;
> +
> + /**
> + * @writeback: Writeback related valriables.
> + */
> + struct drm_writeback_connector writeback;
No, sorry, that's a bad idea. Most connectors have nothing to do with
writeback, you shouldn't introduce writeback-specific fields here.
drm_writeback_connector happens to be a drm_connector because of
historical reasons (it was decided to reuse the connector API exposed to
userspace instead of exposing a completely separate API in order to
simplify the implementation), but that does not mean that every
connector is related to writeback.
I don't know what issues the Intel driver(s) have with
drm_writeback_connector, but you shouldn't make things worse for
everybody due to a driver problem.
> };
>
> #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> index 958466a05e60..2a52b6761797 100644
> --- a/include/drm/drm_writeback.h
> +++ b/include/drm/drm_writeback.h
> @@ -15,66 +15,6 @@
> #include <drm/drm_encoder.h>
> #include <linux/workqueue.h>
>
> -/**
> - * struct drm_writeback_connector - DRM writeback connector
> - */
> -struct drm_writeback_connector {
> - /**
> - * @base: base drm_connector object
> - */
> - struct drm_connector base;
> -
> - /**
> - * @pixel_formats_blob_ptr:
> - *
> - * DRM blob property data for the pixel formats list on writeback
> - * connectors
> - * See also drm_writeback_connector_init()
> - */
> - struct drm_property_blob *pixel_formats_blob_ptr;
> -
> - /** @job_lock: Protects job_queue */
> - spinlock_t job_lock;
> -
> - /**
> - * @job_queue:
> - *
> - * Holds a list of a connector's writeback jobs; the last item is the
> - * most recent. The first item may be either waiting for the hardware
> - * to begin writing, or currently being written.
> - *
> - * See also: drm_writeback_queue_job() and
> - * drm_writeback_signal_completion()
> - */
> - struct list_head job_queue;
> -
> - /**
> - * @fence_context:
> - *
> - * timeline context used for fence operations.
> - */
> - unsigned int fence_context;
> - /**
> - * @fence_lock:
> - *
> - * spinlock to protect the fences in the fence_context.
> - */
> - spinlock_t fence_lock;
> - /**
> - * @fence_seqno:
> - *
> - * Seqno variable used as monotonic counter for the fences
> - * created on the connector's timeline.
> - */
> - unsigned long fence_seqno;
> - /**
> - * @timeline_name:
> - *
> - * The name of the connector's fence timeline.
> - */
> - char timeline_name[32];
> -};
> -
> /**
> * struct drm_writeback_job - DRM writeback job
> */
> @@ -131,10 +71,16 @@ struct drm_writeback_job {
> void *priv;
> };
>
> +static inline struct drm_connector *
> +drm_writeback_to_connector(struct drm_writeback_connector *wb_connector)
> +{
> + return container_of(wb_connector, struct drm_connector, writeback);
> +}
> +
> static inline struct drm_writeback_connector *
> drm_connector_to_writeback(struct drm_connector *connector)
> {
> - return container_of(connector, struct drm_writeback_connector, base);
> + return &connector->writeback;
> }
>
> int drm_writeback_connector_init(struct drm_device *dev,
--
Regards,
Laurent Pinchart
