On 7/1/22 01:06, Laurent Pinchart wrote:
> The media_entity_remote_pad() helper function returns the first remote
The function name is now out of date after the previous patch, it should
be media_entity_remote_pad_first().
Regards,
Hans
> pad it find connected to a given pad. Beside being possibly
> non-deterministic (as it stops at the first enabled link), the fact that
> it returns the first match makes it unsuitable for drivers that need to
> guarantee that a single link is enabled, for instance when an entity can
> process data from one of multiple sources at a time.
>
> For those use cases, add a new helper function,
> media_entity_remote_pad_unique(), that operates on an entity and returns
> a remote pad, with a guarantee that only one link is enabled. To ease
> its use in drivers, also add an inline wrapper that locates source pads
> specifically. A wrapper that locates sink pads can easily be added when
> needed.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Acked-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> Changes since v1:
>
> - Rename media_entity_remote_source_pad() to
> media_entity_remote_source_pad_unique()
> - Skip non-data links
> ---
> Documentation/driver-api/media/mc-core.rst | 3 +-
> drivers/media/mc/mc-entity.c | 40 +++++++++++++++++++
> include/media/media-entity.h | 46 ++++++++++++++++++++++
> 3 files changed, 88 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/driver-api/media/mc-core.rst b/Documentation/driver-api/media/mc-core.rst
> index 6eea6a3b6441..66801506b2dd 100644
> --- a/Documentation/driver-api/media/mc-core.rst
> +++ b/Documentation/driver-api/media/mc-core.rst
> @@ -186,7 +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()` and :c:func:`media_pad_remote_pad_first()`.
> +(:c:func:`media_entity_find_link()`, :c:func:`media_pad_remote_pad_first()` and
> +:c:func:`media_entity_remote_source_pad_unique()`).
>
> Use count and power handling
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> index 55076fea7b58..bd7145932137 100644
> --- a/drivers/media/mc/mc-entity.c
> +++ b/drivers/media/mc/mc-entity.c
> @@ -9,6 +9,7 @@
> */
>
> #include <linux/bitmap.h>
> +#include <linux/list.h>
> #include <linux/property.h>
> #include <linux/slab.h>
> #include <media/media-entity.h>
> @@ -920,6 +921,45 @@ struct media_pad *media_pad_remote_pad_first(const struct media_pad *pad)
> }
> EXPORT_SYMBOL_GPL(media_pad_remote_pad_first);
>
> +struct media_pad *
> +media_entity_remote_pad_unique(const struct media_entity *entity,
> + unsigned int type)
> +{
> + struct media_pad *pad = NULL;
> + struct media_link *link;
> +
> + list_for_each_entry(link, &entity->links, list) {
> + struct media_pad *local_pad;
> + struct media_pad *remote_pad;
> +
> + if (((link->flags & MEDIA_LNK_FL_LINK_TYPE) !=
> + MEDIA_LNK_FL_DATA_LINK) ||
> + !(link->flags & MEDIA_LNK_FL_ENABLED))
> + continue;
> +
> + if (type == MEDIA_PAD_FL_SOURCE) {
> + local_pad = link->sink;
> + remote_pad = link->source;
> + } else {
> + local_pad = link->source;
> + remote_pad = link->sink;
> + }
> +
> + if (local_pad->entity == entity) {
> + if (pad)
> + return ERR_PTR(-ENOTUNIQ);
> +
> + pad = remote_pad;
> + }
> + }
> +
> + if (!pad)
> + return ERR_PTR(-ENOLINK);
> +
> + return pad;
> +}
> +EXPORT_SYMBOL_GPL(media_entity_remote_pad_unique);
> +
> 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 ab84476b25c8..aecd1691b297 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -859,6 +859,52 @@ struct media_link *media_entity_find_link(struct media_pad *source,
> */
> struct media_pad *media_pad_remote_pad_first(const struct media_pad *pad);
>
> +/**
> + * media_entity_remote_pad_unique - Find a remote pad connected to an entity
> + * @entity: The entity
> + * @type: The type of pad to find (MEDIA_PAD_FL_SINK or MEDIA_PAD_FL_SOURCE)
> + *
> + * Search for and return a remote pad of @type connected to @entity through an
> + * enabled link. If multiple (or no) remote pads match these criteria, an error
> + * is returned.
> + *
> + * The uniqueness constraint makes this helper function suitable for entities
> + * that support a single active source or sink at a time.
> + *
> + * 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_entity_remote_pad_unique(const struct media_entity *entity,
> + unsigned int type);
> +
> +/**
> + * media_entity_remote_source_pad_unique - Find a remote source pad connected to
> + * an entity
> + * @entity: The entity
> + *
> + * Search for and return a remote source pad connected to @entity through an
> + * enabled link. If multiple (or no) remote pads match these criteria, an error
> + * is returned.
> + *
> + * The uniqueness constraint makes this helper function suitable for entities
> + * that support a single active source at a time.
> + *
> + * 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
> + */
> +static inline struct media_pad *
> +media_entity_remote_source_pad_unique(const struct media_entity *entity)
> +{
> + return media_entity_remote_pad_unique(entity, MEDIA_PAD_FL_SOURCE);
> +}
> +
> /**
> * media_entity_is_streaming - Test if an entity is part of a streaming pipeline
> * @entity: The entity
