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, 11 insertions, 6 deletions

diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
index 5bc2efe720c2..8670b8e44851 100644
--- a/include/media/v4l2-async.h
+++ b/include/media/v4l2-async.h
@@ -62,27 +62,32 @@ struct v4l2_async_match_desc {
 };
 
 /**
- * struct v4l2_async_connection - connection descriptor, as known to a bridge
+ * struct v4l2_async_connection - sub-device connection descriptor, as known to
+ *				  a bridge
  *
  * @match:	struct of match type and per-bus type matching data sets
+ * @notifier:	the async notifier the connection is related to
  * @asc_entry:	used to add struct v4l2_async_connection objects to the
  *		notifier @waiting_list or @done_list
+ * @asc_subdev_entry:	entry in struct v4l2_async_subdev.asc_list list
  * @sd:		the related sub-device
  *
- * When this struct is used as a member in a driver specific struct,
- * the driver specific struct shall contain the &struct
- * v4l2_async_connection as its first member.
+ * When this struct is used as a member in a driver specific struct, the driver
+ * specific struct shall contain the &struct v4l2_async_connection as its first
+ * member.
  */
 struct v4l2_async_connection {
 	struct v4l2_async_match_desc match;
+	struct v4l2_async_notifier *notifier;
 	struct list_head asc_entry;
+	struct list_head asc_subdev_entry;
 	struct v4l2_subdev *sd;
 };
 
 /**
  * struct v4l2_async_notifier_operations - Asynchronous V4L2 notifier operations
- * @bound:	a subdevice driver has successfully probed one of the subdevices
- * @complete:	All subdevices have been probed successfully. The complete
+ * @bound:	a sub-device has been bound by the given connection
+ * @complete:	All connections have been bound successfully. The complete
  *		callback is only executed for the root notifier.
  * @unbind:	a subdevice is leaving
  * @destroy:	the asc is about to be freed