[PATCH v10 17/24] v4l: fwnode: Add a helper function for parsing generic references

[Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

Add function v4l2_fwnode_reference_count() for counting external
references and v4l2_fwnode_reference_parse() for parsing them as async
sub-devices.

This can be done on e.g. flash or lens async sub-devices that are not part
of but are associated with a sensor.

struct v4l2_async_notifier.max_subdevs field is added to contain the
maximum number of sub-devices in a notifier to reflect the memory
allocated for the subdevs array.

Signed-off-by: Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 drivers/media/v4l2-core/v4l2-fwnode.c | 47 +++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
index d978f2d714ca..4821c4989119 100644
--- a/drivers/media/v4l2-core/v4l2-fwnode.c
+++ b/drivers/media/v4l2-core/v4l2-fwnode.c
@@ -449,6 +449,53 @@ int v4l2_async_notifier_parse_fwnode_endpoints(
 }
 EXPORT_SYMBOL_GPL(v4l2_async_notifier_parse_fwnode_endpoints);
 
+static int v4l2_fwnode_reference_parse(
+	struct device *dev, struct v4l2_async_notifier *notifier,
+	const char *prop)
+{
+	struct fwnode_reference_args args;
+	unsigned int index = 0;
+	int ret;
+
+	for (; !fwnode_property_get_reference_args(
+		     dev_fwnode(dev), prop, NULL, 0, index, &args); index++)
+		fwnode_handle_put(args.fwnode);
+
+	ret = v4l2_async_notifier_realloc(notifier,
+					  notifier->num_subdevs + index);
+	if (ret)
+		return -ENOMEM;
+
+	for (ret = -ENOENT, index = 0;
+	     !fwnode_property_get_reference_args(
+		     dev_fwnode(dev), prop, NULL, 0, index, &args);
+	     index++) {
+		struct v4l2_async_subdev *asd;
+
+		if (WARN_ON(notifier->num_subdevs >= notifier->max_subdevs)) {
+			ret = -EINVAL;
+			goto error;
+		}
+
+		asd = kzalloc(sizeof(*asd), GFP_KERNEL);
+		if (!asd) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		notifier->subdevs[notifier->num_subdevs] = asd;
+		asd->match.fwnode.fwnode = args.fwnode;
+		asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
+		notifier->num_subdevs++;
+	}
+
+	return 0;
+
+error:
+	fwnode_handle_put(args.fwnode);
+	return ret;
+}
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>");
 MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>");
-- 
2.11.0

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