media: v4l: async: Allow multiple connections between entities

When the v4l2-async framework was introduced, the use case for it was to
connect a camera sensor with a parallel receiver. Both tended to be rather
simple devices with a single connection between them.

The framework has been since improved in multiple ways but there are
limitations that have remained, for instance the assumption an async
sub-device is connected towards a single notifier and via a single link
only.

This patch enables connecting a sub-device to one or more notifiers
simultaneously, with one or more connections per notifier. The notifier
information is moved from the sub-device to the connection and the
connections in sub-device are no longer a pointer but a linked list.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # imx6qp
Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> # rcar + adv746x
Tested-by: Aishwarya Kothari <aishwarya.kothari@toradex.com> # Apalis i.MX6Q with TC358743
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> # Renesas RZ/G2L SMARC
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 212d7f1ac525..a8078ae99596 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1022,10 +1022,10 @@ struct v4l2_subdev_platform_data {
  *	    either dev->of_node->fwnode or dev->fwnode (whichever is non-NULL).
  * @async_list: Links this subdev to a global subdev_list or
  *		@notifier->done_list list.
- * @asd: Pointer to respective &struct v4l2_async_connection.
- * @notifier: Pointer to the managing notifier.
  * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
  *		     device using v4l2_async_register_subdev_sensor().
+ * @asc_list: Async connection list, of &struct
+ *	      v4l2_async_connection.subdev_entry.
  * @pdata: common part of subdevice platform data
  * @state_lock: A pointer to a lock used for all the subdev's states, set by the
  *		driver. This is	optional. If NULL, each state instance will get
@@ -1065,9 +1065,8 @@ struct v4l2_subdev {
 	struct device *dev;
 	struct fwnode_handle *fwnode;
 	struct list_head async_list;
-	struct v4l2_async_connection *asd;
-	struct v4l2_async_notifier *notifier;
 	struct v4l2_async_notifier *subdev_notifier;
+	struct list_head asc_list;
 	struct v4l2_subdev_platform_data *pdata;
 	struct mutex *state_lock;