FROMLIST: v4l: fwnode: Add a helper function to obtain device / integer references

v4l2_fwnode_reference_parse_int_prop() will find an fwnode such that under
the device's own fwnode, it will follow child fwnodes with the given
property-value pair and return the resulting fwnode.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
(cherry picked from commit 804b867e30fe9855d9d7810a363a2b8388c2a9aa)
https://git.linuxtv.org/sailus/media_tree.git/log/?h=010f7f4393fd
http://www.spinics.net/lists/linux-media/msg122688.html
Signed-off-by: Marc Herbert <marc.herbert@intel.com>

BUG=b:64133998
TEST=media device topology shows subdevs registered successfully
TEST=no camera regression

Change-Id: I18727c371e64be7e0a3cfa5da4e23274187c0b5a
Reviewed-on: https://chromium-review.googlesource.com/693698
Commit-Ready: Tomasz Figa <tfiga@chromium.org>
Tested-by: Hyungwoo Yang <hyungwoo.yang@intel.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Jacob Chen <jacob2.chen@rock-chips.com>

Author: Sakari Ailus

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

@@ -529,6 +529,207 @@ static int v4l2_fwnode_reference_parse(
 	return ret;
 }
 
+/*
+ * v4l2_fwnode_reference_get_int_prop - parse a reference with integer
+ *					arguments
+ * @dev: struct device pointer
+ * @notifier: notifier for @dev
+ * @prop: the name of the property
+ * @index: the index of the reference to get
+ * @props: the array of integer property names
+ * @nprops: the number of integer property names in @nprops
+ *
+ * Find fwnodes referred to by a property @prop, then under that
+ * iteratively, @nprops times, follow each child node which has a
+ * property in @props array at a given child index the value of which
+ * matches the integer argument at an index.
+ *
+ * For example, if this function was called with arguments and values
+ * @dev corresponding to device "SEN", @prop == "flash-leds", @index
+ * == 1, @props == { "led" }, @nprops == 1, with the ASL snippet below
+ * it would return the node marked with THISONE. The @dev argument in
+ * the ASL below.
+ *
+ *	Device (LED)
+ *	{
+ *		Name (_DSD, Package () {
+ *			ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+ *			Package () {
+ *				Package () { "led0", "LED0" },
+ *				Package () { "led1", "LED1" },
+ *			}
+ *		})
+ *		Name (LED0, Package () {
+ *			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ *			Package () {
+ *				Package () { "led", 0 },
+ *			}
+ *		})
+ *		Name (LED1, Package () {
+ *			// THISONE
+ *			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ *			Package () {
+ *				Package () { "led", 1 },
+ *			}
+ *		})
+ *	}
+ *
+ *	Device (SEN)
+ *	{
+ *		Name (_DSD, Package () {
+ *			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ *			Package () {
+ *				Package () {
+ *					"flash-leds",
+ *					Package () { ^LED, 0, ^LED, 1 },
+ *				}
+ *			}
+ *		})
+ *	}
+ *
+ * where
+ *
+ *	LED	LED driver device
+ *	LED0	First LED
+ *	LED1	Second LED
+ *	SEN	Camera sensor device (or another device the LED is
+ *		related to)
+ *
+ * Return: 0 on success
+ *	   -ENOENT if no entries (or the property itself) were found
+ *	   -EINVAL if property parsing otherwise failed
+ *	   -ENOMEM if memory allocation failed
+ */
+static struct fwnode_handle *v4l2_fwnode_reference_get_int_prop(
+	struct fwnode_handle *fwnode, const char *prop, unsigned int index,
+	const char **props, unsigned int nprops)
+{
+	struct fwnode_reference_args fwnode_args;
+	unsigned int *args = fwnode_args.args;
+	struct fwnode_handle *child;
+	int ret;
+
+	/*
+	 * Obtain remote fwnode as well as the integer arguments.
+	 *
+	 * Note that right now both -ENODATA and -ENOENT may signal
+	 * out-of-bounds access. Return -ENOENT in that case.
+	 */
+	ret = fwnode_property_get_reference_args(fwnode, prop, NULL, nprops,
+						 index, &fwnode_args);
+	if (ret)
+		return ERR_PTR(ret == -ENODATA ? -ENOENT : ret);
+
+	/*
+	 * Find a node in the tree under the referred fwnode corresponding the
+	 * integer arguments.
+	 */
+	fwnode = fwnode_args.fwnode;
+	while (nprops--) {
+		u32 val;
+
+		/* Loop over all child nodes under fwnode. */
+		fwnode_for_each_child_node(fwnode, child) {
+			if (fwnode_property_read_u32(child, *props, &val))
+				continue;
+
+			/* Found property, see if its value matches. */
+			if (val == *args)
+				break;
+		}
+
+		fwnode_handle_put(fwnode);
+
+		/* No property found; return an error here. */
+		if (!child) {
+			fwnode = ERR_PTR(-ENOENT);
+			break;
+		}
+
+		props++;
+		args++;
+		fwnode = child;
+	}
+
+	return fwnode;
+}
+
+/*
+ * v4l2_fwnode_reference_parse_int_props - parse references for async sub-devices
+ * @dev: struct device pointer
+ * @notifier: notifier for @dev
+ * @prop: the name of the property
+ * @props: the array of integer property names
+ * @nprops: the number of integer properties
+ *
+ * Use v4l2_fwnode_reference_get_int_prop to find fwnodes through reference in
+ * property @prop with integer arguments with child nodes matching in properties
+ * @props. Then, set up V4L2 async sub-devices for those fwnodes in the notifier
+ * accordingly.
+ *
+ * While it is technically possible to use this function on DT, it is only
+ * meaningful on ACPI. On Device tree you can refer to any node in the tree but
+ * on ACPI the references are limited to devices.
+ *
+ * Return: 0 on success
+ *	   -ENOENT if no entries (or the property itself) were found
+ *	   -EINVAL if property parsing otherwisefailed
+ *	   -ENOMEM if memory allocation failed
+ */
+static int v4l2_fwnode_reference_parse_int_props(
+	struct device *dev, struct v4l2_async_notifier *notifier,
+	const char *prop, const char **props, unsigned int nprops)
+{
+	struct fwnode_handle *fwnode;
+	unsigned int index;
+	int ret;
+
+	for (index = 0; !IS_ERR((fwnode = v4l2_fwnode_reference_get_int_prop(
+					 dev_fwnode(dev), prop, index, props,
+					 nprops))); index++)
+		fwnode_handle_put(fwnode);
+
+	/*
+	 * Note that right now both -ENODATA and -ENOENT may signal
+	 * out-of-bounds access. Return the error in cases other than that.
+	 */
+	if (PTR_ERR(fwnode) != -ENOENT && PTR_ERR(fwnode) != -ENODATA)
+		return PTR_ERR(fwnode);
+
+	ret = v4l2_async_notifier_realloc(notifier,
+					  notifier->num_subdevs + index);
+	if (ret)
+		return -ENOMEM;
+
+	for (index = 0; !IS_ERR((fwnode = v4l2_fwnode_reference_get_int_prop(
+					 dev_fwnode(dev), prop, index, props,
+					 nprops))); index++) {
+		struct v4l2_async_subdev *asd;
+
+		if (WARN_ON(notifier->num_subdevs >= notifier->max_subdevs)) {
+			ret = -EINVAL;
+			goto error;
+		}
+
+		asd = kzalloc(sizeof(struct v4l2_async_subdev), GFP_KERNEL);
+		if (!asd) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		notifier->subdevs[notifier->num_subdevs] = asd;
+		asd->match.fwnode.fwnode = fwnode;
+		asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
+		notifier->num_subdevs++;
+	}
+
+	return PTR_ERR(fwnode) == -ENOENT ? 0 : PTR_ERR(fwnode);
+
+error:
+	fwnode_handle_put(fwnode);
+	return ret;
+}
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Sakari Ailus <sakari.ailus@linux.intel.com>");
 MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki@samsung.com>");