[PATCH 01/10] backlight: Add backlight_device_get_by_name()

Noralf Trønnes
2020-04-29T12:57:59Z

Add a way to lookup a backlight device based on its name.
Will be used by a USB display gadget getting the name from configfs.

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jingoo Han <jingoohan1@gmail.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
drivers/video/backlight/backlight.c | 21 +++++++++++++++++++++
include/linux/backlight.h | 1 +
2 files changed, 22 insertions(+)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index cac3e35d7630..92d80aa0c0ef 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -432,6 +432,27 @@ struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
}
EXPORT_SYMBOL(backlight_device_get_by_type);

+/**
+ * backlight_device_get_by_name - Get backlight device by name
+ * @name: Device name
+ *
+ * This function looks up a backlight device by its name. It obtains a reference
+ * on the backlight device and it is the caller's responsibility to drop the
+ * reference by calling backlight_put().
+ *
+ * Returns:
+ * A pointer to the backlight device if found, otherwise NULL.
+ */
+struct backlight_device *backlight_device_get_by_name(const char *name)
+{
+ struct device *dev;
+
+ dev = class_find_device_by_name(backlight_class, name);
+
+ return dev ? to_backlight_device(dev) : NULL;
+}
+EXPORT_SYMBOL(backlight_device_get_by_name);
+
/**
* backlight_device_unregister - unregisters a backlight device object.
* @bd: the backlight device object to be unregistered and freed.
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index c7d6b2e8c3b5..56e4580d4f55 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -190,6 +190,7 @@ extern void backlight_force_update(struct backlight_device *bd,
extern int backlight_register_notifier(struct notifier_block *nb);
extern int backlight_unregister_notifier(struct notifier_block *nb);
extern struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
+struct backlight_device *backlight_device_get_by_name(const char *name);
extern int backlight_device_set_brightness(struct backlight_device *bd, unsigned long brightness);

#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
--
2.23.0