[PATCH v4 02/10] property: Add device_get_child_node_count_named()

[Matti Vaittinen]

There are some use-cases where child nodes with a specific name need to
be parsed. In a few cases the data from the found nodes is added to an
array which is allocated based on the number of found nodes. One example
of such use is the IIO subsystem's ADC channel nodes, where the relevant
nodes are named as channel[@N].

Add a helper for counting device's sub-nodes with certain name instead
of open-coding this in every user.

Suggested-by: Jonathan Cameron <jic23 at kernel.org>
Signed-off-by: Matti Vaittinen <mazziesaccount at gmail.com>
---
Revision history:
v3 => v4:
 - New patch as suggested by Jonathan, see discussion in:
https://lore.kernel.org/lkml/20250223161338.5c896280@jic23-huawei/
---
 drivers/base/property.c  | 28 ++++++++++++++++++++++++++++
 include/linux/property.h |  2 ++
 2 files changed, 30 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index c1392743df9c..3f85818183cd 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -945,6 +945,34 @@ unsigned int device_get_child_node_count(const struct device *dev)
 }
 EXPORT_SYMBOL_GPL(device_get_child_node_count);
 
+/**
+ * device_get_child_node_count_named - number of child nodes with given name
+ *
+ * Scan device's child nodes and find all the nodes with a specific name and
+ * return the number of found nodes. Potential '@number' -ending for scanned
+ * names is ignored. Eg,
+ * device_get_child_node_count(dev, "channel");
+ * would match all the nodes:
+ * channel { }, channel at 0 {}, channel at 0xabba {}...
+ *
+ * @dev: Device to count the child nodes for
+ *
+ * Return: the number of child nodes with a matching name for a given device.
+ */
+unsigned int device_get_child_node_count_named(const struct device *dev,
+					       const char *name)
+{
+	struct fwnode_handle *child;
+	unsigned int count = 0;
+
+	device_for_each_child_node(dev, child)
+		if (fwnode_name_eq(child, "channel"))
+			count++;
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(device_get_child_node_count_named);
+
 bool device_dma_supported(const struct device *dev)
 {
 	return fwnode_call_bool_op(dev_fwnode(dev), device_dma_supported);
diff --git a/include/linux/property.h b/include/linux/property.h
index e214ecd241eb..a2770197f76b 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -209,6 +209,8 @@ int fwnode_irq_get(const struct fwnode_handle *fwnode, unsigned int index);
 int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name);
 
 unsigned int device_get_child_node_count(const struct device *dev);
+unsigned int device_get_child_node_count_named(const struct device *dev,
+					       const char *name);
 
 static inline int device_property_read_u8(const struct device *dev,
 					  const char *propname, u8 *val)
-- 
2.48.1

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20250224/38a20783/attachment.sig>