[PATCH v8 17/21] v4l: fwnode: Add convenience function for parsing generic references

[Sakari Ailus <sakari.ailus@linux.intel.com>]

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@linux.intel.com>
---
 drivers/media/v4l2-core/v4l2-fwnode.c | 85 +++++++++++++++++++++++++++++++++++
 include/media/v4l2-fwnode.h           | 28 ++++++++++++
 2 files changed, 113 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
index e6932d7d47b6..8c059a4217b4 100644
--- a/drivers/media/v4l2-core/v4l2-fwnode.c
+++ b/drivers/media/v4l2-core/v4l2-fwnode.c
@@ -453,6 +453,91 @@ int v4l2_async_notifier_parse_fwnode_endpoints(
 }
 EXPORT_SYMBOL_GPL(v4l2_async_notifier_parse_fwnode_endpoints);
 
+static void v4l2_fwnode_print_args(struct fwnode_reference_args *args)
+{
+	unsigned int i;
+
+	for (i = 0; i < args->nargs; i++) {
+		pr_cont(" %u", args->args[i]);
+		if (i + 1 < args->nargs)
+			pr_cont(",");
+	}
+}
+
+int v4l2_fwnode_reference_parse(
+	struct device *dev, struct v4l2_async_notifier *notifier,
+	const char *prop, const char *nargs_prop, unsigned int nargs,
+	size_t asd_struct_size,
+	int (*parse_single)(struct device *dev,
+			    struct fwnode_reference_args *args,
+			    struct v4l2_async_subdev *asd))
+{
+	struct fwnode_reference_args args;
+	unsigned int index = 0;
+	int ret = -ENOENT;
+
+	if (asd_struct_size < sizeof(struct v4l2_async_subdev))
+		return -EINVAL;
+
+	for (; !fwnode_property_get_reference_args(
+		     dev_fwnode(dev), prop, nargs_prop, nargs,
+		     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, nargs_prop, nargs,
+		     index, &args); index++) {
+		struct v4l2_async_subdev *asd;
+
+		if (WARN_ON(notifier->num_subdevs >= notifier->max_subdevs)) {
+			ret = -EINVAL;
+			goto error;
+		}
+
+		asd = kzalloc(asd_struct_size, GFP_KERNEL);
+		if (!asd) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		ret = parse_single ? parse_single(dev, &args, asd) : 0;
+		if (ret < 0) {
+			kfree(asd);
+			if (ret == -ENOTCONN)
+				dev_dbg(dev,
+					"ignoring reference prop \"%s\", nargs_prop \"%s\", nargs %u, index %u",
+					prop, nargs_prop, nargs, index);
+			else
+				dev_warn(dev,
+					 "driver could not parse reference prop \"%s\", nargs_prop \"%s\", nargs %u, index %u",
+					 prop, nargs_prop, nargs, index);
+			v4l2_fwnode_print_args(&args);
+			pr_cont("\n");
+			if (ret == -ENOTCONN)
+				continue;
+			else
+				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;
+}
+EXPORT_SYMBOL_GPL(v4l2_fwnode_reference_parse);
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Sakari Ailus <sakari.ailus@linux.intel.com>");
 MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki@samsung.com>");
diff --git a/include/media/v4l2-fwnode.h b/include/media/v4l2-fwnode.h
index 6d125f26ec84..3ad71241cb20 100644
--- a/include/media/v4l2-fwnode.h
+++ b/include/media/v4l2-fwnode.h
@@ -254,4 +254,32 @@ int v4l2_async_notifier_parse_fwnode_endpoints(
 			      struct v4l2_fwnode_endpoint *vep,
 			      struct v4l2_async_subdev *asd));
 
+/**
+ * v4l2_fwnode_reference_parse - parse references for async sub-devices
+ * @dev: the device node the properties of which are parsed for references
+ * @notifier: the async notifier where the async subdevs will be added
+ * @prop: the name of the property
+ * @nargs_prop: the name of the property in the remote node that specifies the
+ *		number of integer arguments (may be NULL, in that case nargs
+ *		will be used).
+ * @nargs: the number of integer arguments after the reference
+ * @asd_struct_size: the size of the driver's async sub-device struct, including
+ *		     @struct v4l2_async_subdev
+ * @parse_single: driver's callback function for parsing a reference. Optional.
+ *		  Return: 0 on success
+ *			  %-ENOTCONN if the reference is to be skipped. This
+ *				     will not be considered as an error
+ *
+ * Return: 0 on success
+ *	   -ENOMEM if memory allocation failed
+ *	   -EINVAL if property parsing failed
+ */
+int v4l2_fwnode_reference_parse(
+	struct device *dev, struct v4l2_async_notifier *notifier,
+	const char *prop, const char *nargs_prop, unsigned int nargs,
+	size_t asd_struct_size,
+	int (*parse_single)(struct device *dev,
+			    struct fwnode_reference_args *args,
+			    struct v4l2_async_subdev *asd));
+
 #endif /* _V4L2_FWNODE_H */
-- 
2.11.0