[PATCH 30/36] driver core: Introduce device_find_child().

[Greg KH <greg@kroah.com>]

From: Cornelia Huck <cornelia.huck@de.ibm.com>

Introduce device_find_child() to match device_for_each_child().

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 drivers/base/core.c    |   33 +++++++++++++++++++++++++++++++++
 include/linux/device.h |    2 ++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5d11bbd..a29e685 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -750,12 +750,45 @@ int device_for_each_child(struct device
 	return error;
 }
 
+/**
+ * device_find_child - device iterator for locating a particular device.
+ * @parent: parent struct device
+ * @data: Data to pass to match function
+ * @match: Callback function to check device
+ *
+ * This is similar to the device_for_each_child() function above, but it
+ * returns a reference to a device that is 'found' for later use, as
+ * determined by the @match callback.
+ *
+ * The callback should return 0 if the device doesn't match and non-zero
+ * if it does.  If the callback returns non-zero and a reference to the
+ * current device can be obtained, this function will return to the caller
+ * and not iterate over any more devices.
+ */
+struct device * device_find_child(struct device *parent, void *data,
+				  int (*match)(struct device *, void *))
+{
+	struct klist_iter i;
+	struct device *child;
+
+	if (!parent)
+		return NULL;
+
+	klist_iter_init(&parent->klist_children, &i);
+	while ((child = next_device(&i)))
+		if (match(child, data) && get_device(child))
+			break;
+	klist_iter_exit(&i);
+	return child;
+}
+
 int __init devices_init(void)
 {
 	return subsystem_register(&devices_subsys);
 }
 
 EXPORT_SYMBOL_GPL(device_for_each_child);
+EXPORT_SYMBOL_GPL(device_find_child);
 
 EXPORT_SYMBOL_GPL(device_initialize);
 EXPORT_SYMBOL_GPL(device_add);
diff --git a/include/linux/device.h b/include/linux/device.h
index 2d9dc35..0a0370c 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -421,6 +421,8 @@ extern int __must_check device_add(struc
 extern void device_del(struct device * dev);
 extern int device_for_each_child(struct device *, void *,
 		     int (*fn)(struct device *, void *));
+extern struct device *device_find_child(struct device *, void *data,
+					int (*match)(struct device *, void *));
 extern int device_rename(struct device *dev, char *new_name);
 
 /*
-- 
1.4.4.1

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