media: v4l: async: Clean up testing for duplicate async subdevs

There's a need to verify that a single async sub-device isn't being added
multiple times, this would be an error. This takes place at the time of
adding the async sub-device to the notifier's list as well as when the
notifier is added to the global notifier's list.

Use the pointer to the sub-device for testing this instead of an index to
an array that is long gone. (There was an array of async sub-devices in
the notifier before it was converted to a linked list by commit
66beb323 ("media: v4l2: async: Remove notifier subdevs array").)
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>

drivers/media/v4l2-core/v4l2-async.c

@@ -519,23 +519,23 @@ __v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
 }
 
 /*
- * Find out whether an async sub-device was set up already or
- * whether it exists in a given notifier before @this_index.
- * If @this_index < 0, search the notifier's entire @asd_list.
+ * Find out whether an async sub-device was set up already or whether it exists
+ * in a given notifier. The skip_self argument is used to skip testing the same
+ * sub-device in the notifier in case the sub-device has been already added to
+ * the notifier.
  */
 static bool
 v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
-			       struct v4l2_async_subdev *asd, int this_index)
+			       struct v4l2_async_subdev *asd, bool skip_self)
 {
 	struct v4l2_async_subdev *asd_y;
-	int j = 0;
 
 	lockdep_assert_held(&list_lock);
 
 	/* Check that an asd is not being added more than once. */
 	list_for_each_entry(asd_y, &notifier->asd_list, asd_list) {
-		if (this_index >= 0 && j++ >= this_index)
-			break;
+		if (skip_self && asd == asd_y)
+			continue;
 		if (asd_equal(asd, asd_y))
 			return true;
 	}
@@ -550,7 +550,7 @@ v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
 
 static int v4l2_async_nf_asd_valid(struct v4l2_async_notifier *notifier,
 				   struct v4l2_async_subdev *asd,
-				   int this_index)
+				   bool skip_self)
 {
 	struct device *dev = notifier_dev(notifier);
 
@@ -560,7 +560,7 @@ static int v4l2_async_nf_asd_valid(struct v4l2_async_notifier *notifier,
 	switch (asd->match_type) {
 	case V4L2_ASYNC_MATCH_I2C:
 	case V4L2_ASYNC_MATCH_FWNODE:
-		if (v4l2_async_nf_has_async_subdev(notifier, asd, this_index)) {
+		if (v4l2_async_nf_has_async_subdev(notifier, asd, skip_self)) {
 			dev_dbg(dev, "v4l2-async: subdev descriptor already listed in a notifier\n");
 			return -EEXIST;
 		}
@@ -583,7 +583,7 @@ EXPORT_SYMBOL(v4l2_async_nf_init);
 static int __v4l2_async_nf_register(struct v4l2_async_notifier *notifier)
 {
 	struct v4l2_async_subdev *asd;
-	int ret, i = 0;
+	int ret;
 
 	INIT_LIST_HEAD(&notifier->waiting);
 	INIT_LIST_HEAD(&notifier->done);
@@ -591,7 +591,7 @@ static int __v4l2_async_nf_register(struct v4l2_async_notifier *notifier)
 	mutex_lock(&list_lock);
 
 	list_for_each_entry(asd, &notifier->asd_list, asd_list) {
-		ret = v4l2_async_nf_asd_valid(notifier, asd, i++);
+		ret = v4l2_async_nf_asd_valid(notifier, asd, true);
 		if (ret)
 			goto err_unlock;
 
@@ -725,7 +725,7 @@ static int __v4l2_async_nf_add_subdev(struct v4l2_async_notifier *notifier,
 
 	mutex_lock(&list_lock);
 
-	ret = v4l2_async_nf_asd_valid(notifier, asd, -1);
+	ret = v4l2_async_nf_asd_valid(notifier, asd, false);
 	if (ret)
 		goto unlock;