[PATCH 38/55] media: mc-entity: Add a new helper function to get a remote pad for a pad

[Laurent Pinchart]

Hi Hans,

On Fri, Jun 17, 2022 at 01:41:59PM +0200, Hans Verkuil wrote:
> On 6/14/22 21:11, Paul Elder wrote:
> > From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > 
> > The newly added media_entity_remote_source_pad() helper function handles
> > use cases where the entity has a link enabled uniqueness constraint
> > covering all pads. There are use cases where the constraint covers a
> > specific pad only. Add a new media_pad_remote_pad() function to handle
> > this. It operates as media_entity_remote_source_pad(), but on a given
> > pad instead of on the entity.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  Documentation/driver-api/media/mc-core.rst |  4 +--
> >  drivers/media/mc/mc-entity.c               | 31 ++++++++++++++++++++++
> >  include/media/media-entity.h               | 18 +++++++++++++
> >  3 files changed, 51 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/driver-api/media/mc-core.rst b/Documentation/driver-api/media/mc-core.rst
> > index a2d1e32e3abb..83c3bdbf67be 100644
> > --- a/Documentation/driver-api/media/mc-core.rst
> > +++ b/Documentation/driver-api/media/mc-core.rst
> > @@ -186,8 +186,8 @@ is required and the graph structure can be freed normally.
> >  
> >  Helper functions can be used to find a link between two given pads, or a pad
> >  connected to another pad through an enabled link
> > -(:c:func:`media_entity_find_link()`, :c:func:`media_entity_remote_pad()` and
> > -:c:func:`media_entity_remote_source_pad()`).
> > +(:c:func:`media_entity_find_link()`, :c:func:`media_entity_remote_pad()`,
> > +:c:func:`media_entity_remote_source_pad()` and :c:func:`media_pad_remote_pad()`).
> >  
> >  Use count and power handling
> >  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> > index 1febf5a86be6..6429b0510bfb 100644
> > --- a/drivers/media/mc/mc-entity.c
> > +++ b/drivers/media/mc/mc-entity.c
> > @@ -958,6 +958,37 @@ media_entity_remote_pad_unique(const struct media_entity *entity,
> >  }
> >  EXPORT_SYMBOL_GPL(media_entity_remote_pad_unique);
> >  
> > +struct media_pad *media_pad_remote_pad(const struct media_pad *pad)
> > +{
> > +	struct media_pad *found_pad = NULL;
> > +	struct media_link *link;
> > +
> > +	list_for_each_entry(link, &pad->entity->links, list) {
> > +		struct media_pad *remote_pad;
> > +
> > +		if (!(link->flags & MEDIA_LNK_FL_ENABLED))
> > +			continue;
> > +
> > +		if (link->sink == pad)
> > +			remote_pad = link->source;
> > +		else if (link->source == pad)
> > +			remote_pad = link->sink;
> > +		else
> > +			continue;
> > +
> > +		if (found_pad)
> > +			return ERR_PTR(-ENOTUNIQ);
> > +
> > +		found_pad = remote_pad;
> > +	}
> > +
> > +	if (!found_pad)
> > +		return ERR_PTR(-ENOLINK);
> > +
> > +	return found_pad;
> > +}
> > +EXPORT_SYMBOL_GPL(media_pad_remote_pad);
> > +
> >  static void media_interface_init(struct media_device *mdev,
> >  				 struct media_interface *intf,
> >  				 u32 gobj_type,
> > diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> > index 33d5f52719a0..bfe6a7b10a68 100644
> > --- a/include/media/media-entity.h
> > +++ b/include/media/media-entity.h
> > @@ -904,6 +904,24 @@ media_entity_remote_source_pad(const struct media_entity *entity)
> >  	return media_entity_remote_pad_unique(entity, MEDIA_PAD_FL_SOURCE);
> >  }
> >  
> > +/**
> > + * media_pad_remote_pad - Find a remote pad connected to a pad
> 
> Same question here: shouldn't this be called media_pad_remote_pad_unique?

I'm fine with that (and for the previous patch too). I'll wait for
Sakari's opinion and will then make the change.

> > + * @pad: The pad
> > + *
> > + * Search for and return a remote pad connected to @pad through an enabled
> > + * link. If multiple (or no) remote pads are found, an error is returned.
> > + *
> > + * The uniqueness constraint makes this helper function suitable for entities
> > + * that support a single active source at a time on a given pad.
> > + *
> > + * Return: A pointer to the remote pad, or one of the following error pointers
> > + * if an error occurs:
> > + *
> > + * * -ENOTUNIQ - Multiple links are enabled
> > + * * -ENOLINK - No connected pad found
> > + */
> > +struct media_pad *media_pad_remote_pad(const struct media_pad *pad);
> > +
> >  /**
> >   * media_entity_is_streaming - Test if an entity is part of a streaming pipeline
> >   * @entity: The entity
> 
> With that change:
> 
> Acked-by: Hans Verkuil <hverkuil-cisco at xs4all.nl>

-- 
Regards,

Laurent Pinchart