media: v4l: async: Simplify async sub-device fwnode matching

V4L2 async sub-device matching originally used the device nodes only.
Endpoint nodes were taken into use instead as using the device nodes was
problematic for it was in some cases ambiguous which link might have been
in question.

There is however no need to use endpoint nodes on both sides, as the async
sub-device's fwnode can always be trivially obtained using
fwnode_graph_get_remote_endpoint() when needed while what counts is
whether or not the link is between two device nodes, i.e. the device nodes
match.

This will briefly break the adv748x driver but it will be fixed later in
the set, by patch "media: adv748x: Return to endpoint matching".

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, 21 insertions, 67 deletions

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index 04ea6f9a8ed3..11d336e783bd 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -94,89 +94,36 @@ match_fwnode_one(struct v4l2_async_notifier *notifier,
 		 struct v4l2_subdev *sd, struct fwnode_handle *sd_fwnode,
 		 struct v4l2_async_match_desc *match)
 {
-	struct fwnode_handle *other_fwnode;
-	struct fwnode_handle *dev_fwnode;
-	bool asd_fwnode_is_ep;
-	bool sd_fwnode_is_ep;
-	struct device *dev;
+	struct fwnode_handle *asd_dev_fwnode;
+	bool ret;
 
 	dev_dbg(notifier_dev(notifier),
 		"v4l2-async: fwnode match: need %pfw, trying %pfw\n",
 		sd_fwnode, match->fwnode);
 
-	/*
-	 * Both the subdev and the async subdev can provide either an endpoint
-	 * fwnode or a device fwnode. Start with the simple case of direct
-	 * fwnode matching.
-	 */
 	if (sd_fwnode == match->fwnode) {
 		dev_dbg(notifier_dev(notifier),
 			"v4l2-async: direct match found\n");
 		return true;
 	}
 
-	/*
-	 * Otherwise, check if the sd fwnode and the asd fwnode refer to an
-	 * endpoint or a device. If they're of the same type, there's no match.
-	 * Technically speaking this checks if the nodes refer to a connected
-	 * endpoint, which is the simplest check that works for both OF and
-	 * ACPI. This won't make a difference, as drivers should not try to
-	 * match unconnected endpoints.
-	 */
-	sd_fwnode_is_ep = fwnode_graph_is_endpoint(sd_fwnode);
-	asd_fwnode_is_ep = fwnode_graph_is_endpoint(match->fwnode);
-
-	if (sd_fwnode_is_ep == asd_fwnode_is_ep) {
+	if (!fwnode_graph_is_endpoint(match->fwnode)) {
 		dev_dbg(notifier_dev(notifier),
 			"v4l2-async: direct match not found\n");
 		return false;
 	}
 
-	/*
-	 * The sd and asd fwnodes are of different types. Get the device fwnode
-	 * parent of the endpoint fwnode, and compare it with the other fwnode.
-	 */
-	if (sd_fwnode_is_ep) {
-		dev_fwnode = fwnode_graph_get_port_parent(sd_fwnode);
-		other_fwnode = match->fwnode;
-	} else {
-		dev_fwnode = fwnode_graph_get_port_parent(match->fwnode);
-		other_fwnode = sd_fwnode;
-	}
+	asd_dev_fwnode = fwnode_graph_get_port_parent(match->fwnode);
 
-	dev_dbg(notifier_dev(notifier),
-		"v4l2-async: fwnode compat match: need %pfw, trying %pfw\n",
-		dev_fwnode, other_fwnode);
+	ret = sd_fwnode == asd_dev_fwnode;
 
-	fwnode_handle_put(dev_fwnode);
+	fwnode_handle_put(asd_dev_fwnode);
 
-	if (dev_fwnode != other_fwnode) {
-		dev_dbg(notifier_dev(notifier),
-			"v4l2-async: compat match not found\n");
-		return false;
-	}
-
-	/*
-	 * We have a heterogeneous match. Retrieve the struct device of the side
-	 * that matched on a device fwnode to print its driver name.
-	 */
-	if (sd_fwnode_is_ep)
-		dev = notifier->v4l2_dev ? notifier->v4l2_dev->dev
-		    : notifier->sd->dev;
-	else
-		dev = sd->dev;
-
-	if (dev && dev->driver) {
-		if (sd_fwnode_is_ep)
-			dev_warn(dev, "Driver %s uses device fwnode, incorrect match may occur\n",
-				 dev->driver->name);
-		dev_notice(dev, "Consider updating driver %s to match on endpoints\n",
-			   dev->driver->name);
-	}
-
-	dev_dbg(notifier_dev(notifier), "v4l2-async: compat match found\n");
+	dev_dbg(notifier_dev(notifier),
+		"v4l2-async: device--endpoint match %sfound\n",
+		ret ? "" : "not ");
 
-	return true;
+	return ret;
 }
 
 static bool match_fwnode(struct v4l2_async_notifier *notifier,
@@ -816,12 +763,19 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)
 	int ret;
 
 	/*
-	 * No reference taken. The reference is held by the device
-	 * (struct v4l2_subdev.dev), and async sub-device does not
-	 * exist independently of the device at any point of time.
+	 * No reference taken. The reference is held by the device (struct
+	 * v4l2_subdev.dev), and async sub-device does not exist independently
+	 * of the device at any point of time.
+	 *
+	 * The async sub-device shall always be registered for its device node,
+	 * not the endpoint node.
 	 */
-	if (!sd->fwnode && sd->dev)
+	if (!sd->fwnode && sd->dev) {
 		sd->fwnode = dev_fwnode(sd->dev);
+	} else if (fwnode_graph_is_endpoint(sd->fwnode)) {
+		dev_warn(sd->dev, "sub-device fwnode is an endpoint!\n");
+		return -EINVAL;
+	}
 
 	mutex_lock(&list_lock);