device property: Add function to search for named child of device

For device nodes in both DT and ACPI, it possible to have named
child nodes which contain properties (an existing example being
gpio-leds). This adds a function to find a named child node for
a device which can be used by drivers for property retrieval.

For DT data node name matching, of_node_cmp() and similar functions
are made available outside of CONFIG_OF block so the new function
can reference these for DT and non-DT builds.

For ACPI data node name matching, a helper function is also added
which returns false if CONFIG_ACPI is not set, otherwise it
performs a string comparison on the data node name. This avoids
using the acpi_data_node struct for non CONFIG_ACPI builds,
which would otherwise cause a build failure.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Acked-by: Sathyanarayana Nujella <sathyanarayana.nujella@intel.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/base/property.c b/drivers/base/property.c
index f38c21de29b7..43a36d68c3fd 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -888,6 +888,34 @@ struct fwnode_handle *device_get_next_child_node(struct device *dev,
 EXPORT_SYMBOL_GPL(device_get_next_child_node);
 
 /**
+ * device_get_named_child_node - Return first matching named child node handle
+ * @dev: Device to find the named child node for.
+ * @childname: String to match child node name against.
+ */
+struct fwnode_handle *device_get_named_child_node(struct device *dev,
+                                                  const char *childname)
+{
+        struct fwnode_handle *child;
+
+        /*
+         * Find first matching named child node of this device.
+         * For ACPI this will be a data only sub-node.
+         */
+        device_for_each_child_node(dev, child) {
+                if (is_of_node(child)) {
+                        if (!of_node_cmp(to_of_node(child)->name, childname))
+                                return child;
+                } else if (is_acpi_data_node(child)) {
+                        if (acpi_data_node_match(child, childname))
+                                return child;
+                }
+        }
+
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(device_get_named_child_node);
+
+/**
  * fwnode_handle_put - Drop reference to a device node
  * @fwnode: Pointer to the device node to drop the reference to.
  *