Re: [RFC 1/7] media: mc: Add INTERNAL_SOURCE pad type flag

[Hans Verkuil <hverkuil@xs4all.nl>]

On 05/05/2023 23:52, Sakari Ailus wrote:
> Internal source pads will be used as routing endpoints in V4L2
> [GS]_ROUTING IOCTLs, to indicate that the stream begins in the entity.
> 
> Also prevent creating links to pads that have been flagged as internal.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  .../userspace-api/media/mediactl/media-types.rst          | 7 +++++++
>  drivers/media/mc/mc-entity.c                              | 8 +++++++-
>  include/uapi/linux/media.h                                | 1 +
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/userspace-api/media/mediactl/media-types.rst b/Documentation/userspace-api/media/mediactl/media-types.rst
> index 0ffeece1e0c8..c724139ad46c 100644
> --- a/Documentation/userspace-api/media/mediactl/media-types.rst
> +++ b/Documentation/userspace-api/media/mediactl/media-types.rst
> @@ -361,6 +361,7 @@ Types and flags used to represent the media graph elements
>  .. _MEDIA-PAD-FL-SINK:
>  .. _MEDIA-PAD-FL-SOURCE:
>  .. _MEDIA-PAD-FL-MUST-CONNECT:
> +.. _MEDIA-PAD-FL-INTERNAL-SOURCE:
>  
>  .. flat-table:: Media pad flags
>      :header-rows:  0
> @@ -382,6 +383,12 @@ Types and flags used to represent the media graph elements
>  	  when this flag isn't set; the absence of the flag doesn't imply
>  	  there is none.
>  
> +    *  -  ``MEDIA_PAD_FL_INTERNAL_SOURCE``
> +       -  This flag indicates an internal pad that has no external

'internal pad' or 'internal source pad'?

> +	  connections. Such a pad may not be connected with a link. The internal
> +	  flag indicates that the stream either starts or ends in the
> +	  entity.

This sentence makes no sense. The flag is for a pad, but then this sentence
talks about streams and entities and doesn't relate that to the pad. Also,
the flag is INTERNAL_SOURCE, and reading 'stream ends' suggests that it
should be INTERNAL_SINK in that case.

I think this needs to be more elaborate and ideally add some examples
of the use-case(s) (or refer to an example elsewhere).

 For a given pad, the INTERNAL_SOURCE flag may not be set if
> +	  either SINK or SOURCE flags is set.
>  
>  One and only one of ``MEDIA_PAD_FL_SINK`` and ``MEDIA_PAD_FL_SOURCE``

and 'MEDIA_PAD_FL_INTERNAL_SOURCE' as well?

>  must be set for every pad.
> diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> index ef34ddd715c9..ed99160a2487 100644
> --- a/drivers/media/mc/mc-entity.c
> +++ b/drivers/media/mc/mc-entity.c
> @@ -1062,7 +1062,8 @@ int media_get_pad_index(struct media_entity *entity, u32 pad_type,
>  
>  	for (i = 0; i < entity->num_pads; i++) {
>  		if ((entity->pads[i].flags &
> -		     (MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_SOURCE)) != pad_type)
> +		     (MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_SOURCE |
> +		      MEDIA_PAD_FL_INTERNAL_SOURCE)) != pad_type)
>  			continue;
>  
>  		if (entity->pads[i].sig_type == sig_type)
> @@ -1087,6 +1088,11 @@ media_create_pad_link(struct media_entity *source, u16 source_pad,
>  		return -EINVAL;
>  	if (WARN_ON(!(sink->pads[sink_pad].flags & MEDIA_PAD_FL_SINK)))
>  		return -EINVAL;
> +	if (WARN_ON(sink->pads[sink_pad].flags &
> +		    MEDIA_PAD_FL_INTERNAL_SOURCE) ||
> +	    WARN_ON(source->pads[source_pad].flags &
> +		    MEDIA_PAD_FL_INTERNAL_SOURCE))
> +		return -EINVAL;
>  
>  	link = media_add_link(&source->links);
>  	if (link == NULL)
> diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
> index edb8dfef9eba..0e2577e8b425 100644
> --- a/include/uapi/linux/media.h
> +++ b/include/uapi/linux/media.h
> @@ -208,6 +208,7 @@ struct media_entity_desc {
>  #define MEDIA_PAD_FL_SINK			(1U << 0)
>  #define MEDIA_PAD_FL_SOURCE			(1U << 1)
>  #define MEDIA_PAD_FL_MUST_CONNECT		(1U << 2)
> +#define MEDIA_PAD_FL_INTERNAL_SOURCE		(1U << 3)
>  
>  struct media_pad_desc {
>  	__u32 entity;		/* entity ID */

Regards,

	Hans