Re: [PATCH v5 2/4] drm: introduce drm_writeback_connector_init_with_encoder() API

On Mon, Mar 21, 2022 at 04:56:43PM -0700, Abhinav Kumar wrote:

For vendors drivers which pass an already allocated and initialized encoder especially for cases where the encoder hardware is shared OR the writeback encoder shares the resources with the rest of the display pipeline introduce a new API, drm_writeback_connector_init_with_encoder() which expects an initialized encoder as a parameter and only sets up the writeback connector.

changes in v5:

• reorder this change to come before in the series to avoid incorrect functionality in subsequent changes
• continue using struct drm_encoder instead of struct drm_encoder * and switch it in next change

Signed-off-by: Abhinav Kumar quic_abhinavk@quicinc.com

Hi Abhinav,

---

drivers/gpu/drm/drm_writeback.c | 143 ++++++++++++++++++++++++++++------------ include/drm/drm_writeback.h | 5 ++ 2 files changed, 106 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c index dc2ef12..abe78b9 100644 --- a/drivers/gpu/drm/drm_writeback.c +++ b/drivers/gpu/drm/drm_writeback.c @@ -149,37 +149,15 @@ static const struct drm_encoder_funcs drm_writeback_encoder_funcs = { .destroy = drm_encoder_cleanup, };

-/**

• • drm_writeback_connector_init - Initialize a writeback connector and its properties
• • @dev: DRM device
• • @wb_connector: Writeback connector to initialize
• • @con_funcs: Connector funcs vtable
• • @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
• • @formats: Array of supported pixel formats for the writeback engine
• • @n_formats: Length of the formats array
• • @possible_crtcs: possible crtcs for the internal writeback encoder
• • This function creates the writeback-connector-specific properties if they
• • have not been already created, initializes the connector as
• • type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
• • values. It will also create an internal encoder associated with the
• • drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
• • the encoder helper.
• • Drivers should always use this function instead of drm_connector_init() to
• • set up writeback connectors.
• • Returns: 0 on success, or a negative error code
• */

-int drm_writeback_connector_init(struct drm_device *dev,

• 		 struct drm_writeback_connector *wb_connector,
  

• 		 const struct drm_connector_funcs *con_funcs,
  

• 		 const struct drm_encoder_helper_funcs *enc_helper_funcs,
  

• 		 const u32 *formats, int n_formats, uint32_t possible_crtcs)
  

+static int drm_writeback_connector_setup(struct drm_device *dev,

• struct drm_writeback_connector *wb_connector,
  

• const struct drm_connector_funcs *con_funcs, const u32 *formats,
  

• int n_formats)
  

{ struct drm_property_blob *blob;

• struct drm_connector *connector = &wb_connector->base; struct drm_mode_config *config = &dev->mode_config;

• struct drm_connector *connector = &wb_connector->base;

Point of this reordering the statements is...?

int ret = create_writeback_properties(dev);

if (ret != 0) @@ -187,18 +165,10 @@ int drm_writeback_connector_init(struct drm_device *dev,

blob = drm_property_create_blob(dev, n_formats * sizeof(*formats), formats);

• if (IS_ERR(blob))

• return PTR_ERR(blob);
  

• drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
• wb_connector->encoder.possible_crtcs = possible_crtcs;
• ret = drm_encoder_init(dev, &wb_connector->encoder,

• 	       &drm_writeback_encoder_funcs,
  

• 	       DRM_MODE_ENCODER_VIRTUAL, NULL);
  

• if (ret)

• goto fail;
  

• if (IS_ERR(blob)) {

• ret = PTR_ERR(blob);
  

• return ret;
  

• }

I don't see why you have changed the earlier code to store the result of PTR_ERR into ret other than to help your debugging. I suggest that you keep the existing code that returns PTR_ERR(blob) directly and you will have a nicer diff stat as well.

connector->interlace_allowed = 0;

@@ -237,13 +207,102 @@ int drm_writeback_connector_init(struct drm_device *dev, attach_fail: drm_connector_cleanup(connector); connector_fail:

• drm_encoder_cleanup(&wb_connector->encoder);

-fail: drm_property_blob_put(blob); return ret; }

+/**

• • drm_writeback_connector_init - Initialize a writeback connector and its properties
• • @dev: DRM device
• • @wb_connector: Writeback connector to initialize
• • @con_funcs: Connector funcs vtable
• • @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
• • @formats: Array of supported pixel formats for the writeback engine
• • @n_formats: Length of the formats array
• • @possible_crtcs: possible crtcs for the internal writeback encoder
• • This function creates the writeback-connector-specific properties if they
• • have not been already created, initializes the connector as
• • type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
• • values. It will also create an internal encoder associated with the
• • drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
• • the encoder helper.
• • Drivers should always use this function instead of drm_connector_init() to
• • set up writeback connectors.
• • Returns: 0 on success, or a negative error code
• */

+int drm_writeback_connector_init(struct drm_device *dev,

• struct drm_writeback_connector *wb_connector,
  

• const struct drm_connector_funcs *con_funcs,
  

• const struct drm_encoder_helper_funcs *enc_helper_funcs,
  

• const u32 *formats, int n_formats, uint32_t possible_crtcs)
  

+{

• int ret = 0;
• drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
• wb_connector->encoder.possible_crtcs = possible_crtcs;
• ret = drm_encoder_init(dev, &wb_connector->encoder,

• 	       &drm_writeback_encoder_funcs,
  

• 	       DRM_MODE_ENCODER_VIRTUAL, NULL);
  

• if (ret)

• return ret;
  

• ret = drm_writeback_connector_setup(dev, wb_connector, con_funcs, formats,

• 	n_formats);
  

• if (ret)

• drm_encoder_cleanup(&wb_connector->encoder);
  

• return ret;

+} EXPORT_SYMBOL(drm_writeback_connector_init);

+/**

• • drm_writeback_connector_init_with_encoder - Initialize a writeback connector and its properties
• • using the encoder which already assigned and initialized
• • @dev: DRM device
• • @wb_connector: Writeback connector to initialize
• • @con_funcs: Connector funcs vtable
• • @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
• • @formats: Array of supported pixel formats for the writeback engine
• • @n_formats: Length of the formats array
• • This function creates the writeback-connector-specific properties if they
• • have not been already created, initializes the connector as
• • type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
• • values.
• • This function assumes that the drm_writebac_connector's encoder has already been

spelling: writeback

• • created and initialized before invoking this function.
• • In addition, this function also assumes that callers of this API will manage
• • assigning the encoder helper functions, possible_crtcs and any other encoder
• • specific operation which is otherwise handled by drm_writeback_connector_init().
• • Drivers should always use this function instead of drm_connector_init() to
• • set up writeback connectors.

.... if they want to manage themselves the lifetime of the associated encoder.

We're not trying to replace drm_writeback_connector_init() function here, only to provide an alternative function to call for special cases.

• • Returns: 0 on success, or a negative error code
• */

+int drm_writeback_connector_init_with_encoder(struct drm_device *dev,

• struct drm_writeback_connector *wb_connector,
  

• const struct drm_connector_funcs *con_funcs, const u32 *formats,
  

• int n_formats)
  

Where is the encoder parameter? Isn't that the reason why the function is called `_with_encoder`?

I think there might have been too many version of these patchsets and things are starting to be confusing. Please revisit the series without rushing and come up with a plan of action. My understanding of watching this series has been that you're trying to come up with a function that does *connector* initialisation but skips the *encoder* initialisation because it might have been already done by the driver. The idea will be then to have a function `drm_writeback_connector_init_with_encoder()` that does *all* the work that `drm_writeback_connector_init()` does at the moment minus the encoder initialisation part. Then `drm_writeback_connector_init()` only initialises the internal encoder and calls `drm_writeback_connector_init_with_encoder()`. There is no need to have the `drm_writeback_connector_setup()` function at all.

Best regards, Liviu

+{

• int ret = 0;
• ret = drm_writeback_connector_setup(dev, wb_connector, con_funcs, formats,

• 	n_formats);
  

• return ret;

+} +EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);

int drm_writeback_set_fb(struct drm_connector_state *conn_state, struct drm_framebuffer *fb) { diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h index db6214f..0093bab 100644 --- a/include/drm/drm_writeback.h +++ b/include/drm/drm_writeback.h @@ -152,6 +152,11 @@ int drm_writeback_connector_init(struct drm_device *dev, const struct drm_encoder_helper_funcs *enc_helper_funcs, const u32 *formats, int n_formats, uint32_t possible_crtcs);

+int drm_writeback_connector_init_with_encoder(struct drm_device *dev,

• 		struct drm_writeback_connector *wb_connector,
  

• 		const struct drm_connector_funcs *con_funcs, const u32 *formats,
  

• 		int n_formats);
  

int drm_writeback_set_fb(struct drm_connector_state *conn_state, struct drm_framebuffer *fb);

-- 2.7.4