linux-kernel - [PATCH v2 05/12] driver core: Add helper device_find_child_by

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Message-Id: <20190410152505.87041-6-heikki.krogerus@linux.intel.com>
Date:   Wed, 10 Apr 2019 18:24:58 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: [PATCH v2 05/12] driver core: Add helper device_find_child_by_name()

It looks like the child device is often matched with a name.
This introduces a helper that does it automatically.

Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
---
 drivers/base/core.c    | 31 +++++++++++++++++++++++++++++++
 include/linux/device.h |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4aeaa0c92bda..5819ba4c9d4c 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2469,6 +2469,37 @@ struct device *device_find_child(struct device *parent, void *data,
 }
 EXPORT_SYMBOL_GPL(device_find_child);
 
+/**
+ * device_find_child_by_name - device iterator for locating a child device.
+ * @parent: parent struct device
+ * @name: name of the child device
+ *
+ * This is similar to the device_find_child() function above, but it
+ * returns a reference to a device that has the name @name.
+ *
+ * The callback should return NULL if the child is not found and a reference to
+ * the child device if it is found.
+ *
+ * NOTE: you will need to drop the reference with put_device() after use.
+ */
+struct device *device_find_child_by_name(struct device *parent,
+					 const char *name)
+{
+	struct klist_iter i;
+	struct device *child;
+
+	if (!parent)
+		return NULL;
+
+	klist_iter_init(&parent->p->klist_children, &i);
+	while ((child = next_device(&i)))
+		if (!strcmp(dev_name(child), name) && get_device(child))
+			break;
+	klist_iter_exit(&i);
+	return child;
+}
+EXPORT_SYMBOL_GPL(device_find_child_by_name);
+
 int __init devices_init(void)
 {
 	devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
diff --git a/include/linux/device.h b/include/linux/device.h
index 4457e560bc2b..fadb84dd07f9 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1250,6 +1250,8 @@ extern int device_for_each_child_reverse(struct device *dev, void *data,
 		     int (*fn)(struct device *dev, void *data));
 extern struct device *device_find_child(struct device *dev, void *data,
 				int (*match)(struct device *dev, void *data));
+extern struct device *device_find_child_by_name(struct device *parent,
+						const char *name);
 extern int device_rename(struct device *dev, const char *new_name);
 extern int device_move(struct device *dev, struct device *new_parent,
 		       enum dpm_order dpm_order);
-- 
2.20.1