[PATCH v4 15/45] media: media-entity: Add helper to get a single enabled link

Paul Kocialkowski
2022-04-15T15:29:06Z

In a situation where multiple links can be connected to the same
pad of an entity, drivers might need to ensure that only a single
link is enabled to apply appropriate routing (when the hardware can
only use one at a time).

Add a helper to return the single enabled link of an entity given
a specific pad index, which errors out when zero or more than one
link candidates are found.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
drivers/media/mc/mc-entity.c | 26 ++++++++++++++++++++++++++
include/media/media-entity.h | 13 +++++++++++++
2 files changed, 39 insertions(+)

diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
index 8ab0913d8d82..dafd99486d7c 100644
--- a/drivers/media/mc/mc-entity.c
+++ b/drivers/media/mc/mc-entity.c
@@ -878,6 +878,32 @@ media_entity_find_link(struct media_pad *source, struct media_pad *sink)
}
EXPORT_SYMBOL_GPL(media_entity_find_link);

+struct media_link *
+media_entity_get_single_enabled_link(struct media_entity *entity,
+ u16 pad_index)
+{
+ struct media_link *candidate = ERR_PTR(-ENODEV);
+ struct media_link *link;
+
+ list_for_each_entry(link, &entity->links, list) {
+ struct media_pad *pad = link->sink->entity == entity ?
+ link->sink : link->source;
+
+ if (pad->index != pad_index ||
+ !(link->flags & MEDIA_LNK_FL_ENABLED))
+ continue;
+
+ /* Error out with more than a single candidate. */
+ if (candidate != ERR_PTR(-ENODEV))
+ return ERR_PTR(-ENXIO);
+
+ candidate = link;
+ }
+
+ return candidate;
+}
+EXPORT_SYMBOL_GPL(media_entity_get_single_enabled_link);
+
struct media_pad *media_entity_remote_pad(const struct media_pad *pad)
{
struct media_link *link;
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 742918962d46..ee87224d4a89 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -847,6 +847,19 @@ int media_entity_setup_link(struct media_link *link, u32 flags);
struct media_link *media_entity_find_link(struct media_pad *source,
struct media_pad *sink);

+/**
+ * media_entity_get_single_enabled_link - Get a single link for an entity pad
+ * @entity: The entity
+ * @pad_index: The index of the entity's pad expected to take part in link
+ *
+ * Return: returns a pointer to the single enabled link with the entity's pad.
+ * If no such link exists, returns a pointer error with %-ENODEV.
+ * If more than a single link exist, returns a pointer error with %-ENXIO.
+ */
+struct media_link *
+media_entity_get_single_enabled_link(struct media_entity *entity,
+ u16 pad_index);
+
/**
* media_entity_remote_pad - Find the pad at the remote end of a link
* @pad: Pad at the local end of the link
--
2.35.2