3  * Backlight Lowlevel Control Abstraction
14 #include <linux/backlight.h>
22 #include <asm/backlight.h>
28  * The backlight core supports implementing backlight drivers.
30  * A backlight driver registers a driver using
31  * devm_backlight_device_register(). The properties of the backlight
34  * the update_status() operation is called. The backlight driver shall
35  * implement this operation and use it to adjust backlight.
37  * Several sysfs attributes are provided by the backlight core::
43  * See Documentation/ABI/stable/sysfs-class-backlight for the full list.
45  * The backlight can be adjusted using the sysfs interface, and
46  * the backlight driver may also support adjusting backlight using
54  * When the backlight changes this is reported to user-space using
57  * a hot-key to adjust backlight, the driver must notify the backlight
60  * The backlight driver core receives notifications from fbdev and
62  * FBIOBLANK ioctrl, results in a change in the backlight state the
88  * framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK
92  * There may be several fbdev's connected to the backlight device,
94  * if there is a change in backlight for the specified fbdev.
370  * backlight_force_update - tell the backlight subsystem that hardware state
372  * @bd: the backlight device to update
375  * Updates the internal state of the backlight in response to a hardware event,
376  * and generates an uevent to notify userspace. A backlight driver shall call
377  * backlight_force_update() when the backlight is changed using, for example,
420 			WARN(1, "%s: invalid backlight type", name);  in backlight_device_register()
459 /** backlight_device_get_by_type - find first backlight device of a type
460  * @type: the type of backlight device
462  * Look up the first backlight device of the specified type
466  * Pointer to backlight device if any was found. Otherwise NULL.
487  * backlight_device_get_by_name - Get backlight device by name
490  * This function looks up a backlight device by its name. It obtains a reference
491  * on the backlight device and it is the caller's responsibility to drop the
495  * A pointer to the backlight device if found, otherwise NULL.
538 	struct backlight_device *backlight = *(struct backlight_device **)res;  in devm_backlight_device_release()  local
540 	backlight_device_unregister(backlight);  in devm_backlight_device_release()
552  * backlight_register_notifier - get notified of backlight (un)registration
553  * @nb: notifier block with the notifier to call on backlight (un)registration
555  * Register a notifier to get notified when backlight devices get registered
569  * backlight_unregister_notifier - unregister a backlight notifier
572  * Register a notifier to get notified when backlight devices get registered
586  * devm_backlight_device_register - register a new backlight device
591  * @ops: the backlight operations structure
592  * @props: the backlight properties
594  * Creates and registers new backlight device. When a backlight device
600  * struct backlight on success, or an ERR_PTR on error
607 	struct backlight_device **ptr, *backlight;  in devm_backlight_device_register()  local
614 	backlight = backlight_device_register(name, parent, devdata, ops,  in devm_backlight_device_register()
616 	if (!IS_ERR(backlight)) {  in devm_backlight_device_register()
617 		*ptr = backlight;  in devm_backlight_device_register()
623 	return backlight;  in devm_backlight_device_register()
628  * devm_backlight_device_unregister - unregister backlight device
630  * @bd: the backlight device to unregister
632  * Deallocates a backlight allocated with devm_backlight_device_register().
654  * of_find_backlight_by_node() - find backlight device by device-tree node
655  * @node: device-tree node of the backlight device
657  * Returns a pointer to the backlight device corresponding to the given DT
658  * node or NULL if no such backlight device exists or if the device hasn't
661  * This function obtains a reference on the backlight device and it is the
663  * the backlight device's .dev field.
685 		np = of_parse_phandle(dev->of_node, "backlight", 0);  in of_find_backlight()
712  * devm_of_find_backlight - find backlight for a device
715  * This function looks for a property named 'backlight' on the DT node
716  * connected to @dev and looks up the backlight device. The lookup is
717  * device managed so the reference to the backlight device is automatically
722  * A pointer to the backlight device if found.
723  * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
724  * device is found. NULL if there's no backlight property.
750 	backlight_class = class_create(THIS_MODULE, "backlight");  in backlight_class_init()
752 		pr_warn("Unable to create backlight class; errno = %ld\n",  in backlight_class_init()
775 MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");