Re: [PATCH v2 03/10] videobuf2-core: Add helper to get buffer private data from media request

[Paul Kocialkowski]

Hi,

On Thu, 2018-04-19 at 17:41 +0200, Paul Kocialkowski wrote:
> When calling media operation driver callbacks related to media
> requests,
> only a pointer to the request itself is provided, which is
> insufficient
> to retrieve the driver's context. Since the driver context is usually
> set as vb2 queue private data and given that the core can determine
> which objects attached to the request are buffers, it is possible to
> extract the associated private data for the first buffer found.
> 
> This is required in order to access the current m2m context from m2m
> drivers' private data in the context of media request operation
> callbacks. More specifically, this allows scheduling m2m device runs
> from the newly-introduced request complete operation.

This patch too will be dropped since it's no longer useful with the
latest version of the request API.

> Signed-off-by: Paul Kocialkowski 
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 15 +++
>  include/media/videobuf2-core.h  |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index 13c9d9e243dd..6fa46bfc620f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1351,6 +1351,21 @@ bool vb2_core_request_has_buffers(struct
> media_request *req)
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_request_has_buffers);
>  
> +void *vb2_core_request_find_buffer_priv(struct media_request *req)
> +{
> + struct media_request_object *obj;
> + struct vb2_buffer *vb;
> +
> + obj = media_request_object_find(req, _core_req_ops,
> NULL);
> + if (!obj)
> + return NULL;
> +
> + vb = container_of(obj, struct vb2_buffer, req_obj);
> +
> + return vb2_get_drv_priv(vb->vb2_queue);
> +}
> +EXPORT_SYMBOL_GPL(vb2_core_request_find_buffer_priv);
> +
>  int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index,
> void *pb,
>struct media_request *req)
>  {
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-
> core.h
> index 032bd1bec555..65c0cf6afb55 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -1153,4 +1153,5 @@ int vb2_verify_memory_type(struct vb2_queue *q,
>   enum vb2_memory memory, unsigned int type);
>  
>  bool vb2_core_request_has_buffers(struct media_request *req);
> +void *vb2_core_request_find_buffer_priv(struct media_request *req);
>  #endif /* _MEDIA_VIDEOBUF2_CORE_H */
-- 
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com

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Re: [PATCH v2 03/10] videobuf2-core: Add helper to get buffer private data from media request

[Sakari Ailus]

Hi Paul,

On Thu, Apr 19, 2018 at 05:41:17PM +0200, Paul Kocialkowski wrote:
> When calling media operation driver callbacks related to media requests,
> only a pointer to the request itself is provided, which is insufficient
> to retrieve the driver's context. Since the driver context is usually
> set as vb2 queue private data and given that the core can determine
> which objects attached to the request are buffers, it is possible to
> extract the associated private data for the first buffer found.
> 
> This is required in order to access the current m2m context from m2m
> drivers' private data in the context of media request operation
> callbacks. More specifically, this allows scheduling m2m device runs
> from the newly-introduced request complete operation.

Rather than fetching a random buffer from the request objects, I'd suggest
to allocate a struct that contains the media request and place the required
information there.

Such as was in my older patchset. The patch won't apply but the approach
would be useful I think.



> 
> Signed-off-by: Paul Kocialkowski 
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 15 +++
>  include/media/videobuf2-core.h  |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c 
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index 13c9d9e243dd..6fa46bfc620f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1351,6 +1351,21 @@ bool vb2_core_request_has_buffers(struct media_request 
> *req)
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_request_has_buffers);
>  
> +void *vb2_core_request_find_buffer_priv(struct media_request *req)
> +{
> + struct media_request_object *obj;
> + struct vb2_buffer *vb;
> +
> + obj = media_request_object_find(req, _core_req_ops, NULL);
> + if (!obj)
> + return NULL;
> +
> + vb = container_of(obj, struct vb2_buffer, req_obj);
> +
> + return vb2_get_drv_priv(vb->vb2_queue);
> +}
> +EXPORT_SYMBOL_GPL(vb2_core_request_find_buffer_priv);
> +
>  int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb,
>struct media_request *req)
>  {
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 032bd1bec555..65c0cf6afb55 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -1153,4 +1153,5 @@ int vb2_verify_memory_type(struct vb2_queue *q,
>   enum vb2_memory memory, unsigned int type);
>  
>  bool vb2_core_request_has_buffers(struct media_request *req);
> +void *vb2_core_request_find_buffer_priv(struct media_request *req);
>  #endif /* _MEDIA_VIDEOBUF2_CORE_H */
> -- 
> 2.16.3
> 

-- 
Sakari Ailus
sakari.ai...@linux.intel.com

Re: [PATCH v2 03/10] videobuf2-core: Add helper to get buffer private data from media request

[Hans Verkuil]

On 04/19/18 17:41, Paul Kocialkowski wrote:
> When calling media operation driver callbacks related to media requests,
> only a pointer to the request itself is provided, which is insufficient
> to retrieve the driver's context. Since the driver context is usually
> set as vb2 queue private data and given that the core can determine
> which objects attached to the request are buffers, it is possible to
> extract the associated private data for the first buffer found.
> 
> This is required in order to access the current m2m context from m2m
> drivers' private data in the context of media request operation
> callbacks. More specifically, this allows scheduling m2m device runs
> from the newly-introduced request complete operation.
> 
> Signed-off-by: Paul Kocialkowski 
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 15 +++
>  include/media/videobuf2-core.h  |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c 
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index 13c9d9e243dd..6fa46bfc620f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1351,6 +1351,21 @@ bool vb2_core_request_has_buffers(struct media_request 
> *req)
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_request_has_buffers);
>  
> +void *vb2_core_request_find_buffer_priv(struct media_request *req)
> +{
> + struct media_request_object *obj;
> + struct vb2_buffer *vb;
> +
> + obj = media_request_object_find(req, _core_req_ops, NULL);

This increases the object refcount but it is never decreased here.

> + if (!obj)
> + return NULL;
> +
> + vb = container_of(obj, struct vb2_buffer, req_obj);
> +
> + return vb2_get_drv_priv(vb->vb2_queue);

You need to add a media_request_object_put(obj); before returning here.

Regards,

Hans

> +}
> +EXPORT_SYMBOL_GPL(vb2_core_request_find_buffer_priv);
> +
>  int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb,
>struct media_request *req)
>  {
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 032bd1bec555..65c0cf6afb55 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -1153,4 +1153,5 @@ int vb2_verify_memory_type(struct vb2_queue *q,
>   enum vb2_memory memory, unsigned int type);
>  
>  bool vb2_core_request_has_buffers(struct media_request *req);
> +void *vb2_core_request_find_buffer_priv(struct media_request *req);
>  #endif /* _MEDIA_VIDEOBUF2_CORE_H */
> 

[PATCH v2 03/10] videobuf2-core: Add helper to get buffer private data from media request

[Paul Kocialkowski]

When calling media operation driver callbacks related to media requests,
only a pointer to the request itself is provided, which is insufficient
to retrieve the driver's context. Since the driver context is usually
set as vb2 queue private data and given that the core can determine
which objects attached to the request are buffers, it is possible to
extract the associated private data for the first buffer found.

This is required in order to access the current m2m context from m2m
drivers' private data in the context of media request operation
callbacks. More specifically, this allows scheduling m2m device runs
from the newly-introduced request complete operation.

Signed-off-by: Paul Kocialkowski 
---
 drivers/media/common/videobuf2/videobuf2-core.c | 15 +++
 include/media/videobuf2-core.h  |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c 
b/drivers/media/common/videobuf2/videobuf2-core.c
index 13c9d9e243dd..6fa46bfc620f 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -1351,6 +1351,21 @@ bool vb2_core_request_has_buffers(struct media_request 
*req)
 }
 EXPORT_SYMBOL_GPL(vb2_core_request_has_buffers);
 
+void *vb2_core_request_find_buffer_priv(struct media_request *req)
+{
+   struct media_request_object *obj;
+   struct vb2_buffer *vb;
+
+   obj = media_request_object_find(req, _core_req_ops, NULL);
+   if (!obj)
+   return NULL;
+
+   vb = container_of(obj, struct vb2_buffer, req_obj);
+
+   return vb2_get_drv_priv(vb->vb2_queue);
+}
+EXPORT_SYMBOL_GPL(vb2_core_request_find_buffer_priv);
+
 int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb,
 struct media_request *req)
 {
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 032bd1bec555..65c0cf6afb55 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -1153,4 +1153,5 @@ int vb2_verify_memory_type(struct vb2_queue *q,
enum vb2_memory memory, unsigned int type);
 
 bool vb2_core_request_has_buffers(struct media_request *req);
+void *vb2_core_request_find_buffer_priv(struct media_request *req);
 #endif /* _MEDIA_VIDEOBUF2_CORE_H */
-- 
2.16.3