From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
The media_entity_remote_pad() helper function returns the first remote
pad it find connected to a given pad. Beside being possibly ill-named
(as it operates on a pad, not an entity) and 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>
---
Documentation/driver-api/media/mc-core.rst | 4 +-
drivers/media/mc/mc-entity.c | 38 ++++++++++++++++++
include/media/media-entity.h | 45 ++++++++++++++++++++++
3 files changed, 85 insertions(+), 2 deletions(-)
diff --git a/Documentation/driver-api/media/mc-core.rst b/Documentation/driver-api/media/mc-core.rst
index 02481a2513b9..a2d1e32e3abb 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()` and
-:c:func:`media_entity_remote_pad()`.
+(:c:func:`media_entity_find_link()`, :c:func:`media_entity_remote_pad()` and
+:c:func:`media_entity_remote_source_pad()`).
Use count and power handling
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
index 11f5207f73aa..1febf5a86be6 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 +921,43 @@ struct media_pad *media_entity_remote_pad(const struct media_pad *pad)
}
EXPORT_SYMBOL_GPL(media_entity_remote_pad);
+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_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 a9a1c0ec5d1c..33d5f52719a0 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -859,6 +859,51 @@ struct media_link *media_entity_find_link(struct media_pad *source,
*/
struct media_pad *media_entity_remote_pad(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 - 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(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
--
2.30.2
