1 // SPDX-License-Identifier: GPL-2.0-only
3 * Backlight Lowlevel Control Abstraction
5 * Copyright (C) 2003,2004 Hewlett-Packard Company
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/device.h>
14 #include <linux/backlight.h>
15 #include <linux/notifier.h>
16 #include <linux/ctype.h>
17 #include <linux/err.h>
19 #include <linux/slab.h>
21 #ifdef CONFIG_PMAC_BACKLIGHT
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
32 * driver such as type and max_brightness must be specified.
33 * When the core detect changes in for example brightness or power state
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::
39 * - brightness R/W, set the requested brightness level
40 * - actual_brightness RO, the brightness level used by the HW
41 * - max_brightness RO, the maximum brightness level supported
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
47 * a hot-key or some other platform or firmware specific way.
49 * The driver must implement the get_brightness() operation if
50 * the HW do not support all the levels that can be specified in
51 * brightness, thus providing user-space access to the actual level
52 * via the actual_brightness attribute.
54 * When the backlight changes this is reported to user-space using
55 * an uevent connected to the actual_brightness attribute.
56 * When brightness is set by platform specific means, for example
57 * a hot-key to adjust backlight, the driver must notify the backlight
58 * core that brightness has changed using backlight_force_update().
60 * The backlight driver core receives notifications from fbdev and
61 * if the event is FB_EVENT_BLANK and if the value of blank, from the
62 * FBIOBLANK ioctrl, results in a change in the backlight state the
63 * update_status() operation is called.
66 static struct list_head backlight_dev_list
;
67 static struct mutex backlight_dev_list_mutex
;
68 static struct blocking_notifier_head backlight_notifier
;
70 static const char *const backlight_types
[] = {
71 [BACKLIGHT_RAW
] = "raw",
72 [BACKLIGHT_PLATFORM
] = "platform",
73 [BACKLIGHT_FIRMWARE
] = "firmware",
76 static const char *const backlight_scale_types
[] = {
77 [BACKLIGHT_SCALE_UNKNOWN
] = "unknown",
78 [BACKLIGHT_SCALE_LINEAR
] = "linear",
79 [BACKLIGHT_SCALE_NON_LINEAR
] = "non-linear",
82 #if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
83 defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
85 * fb_notifier_callback
87 * This callback gets called when something important happens inside a
88 * framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK
89 * which is reported to the driver using backlight_update_status()
92 * There may be several fbdev's connected to the backlight device,
93 * in which case they are kept track of. A state change is only reported
94 * if there is a change in backlight for the specified fbdev.
96 static int fb_notifier_callback(struct notifier_block
*self
,
97 unsigned long event
, void *data
)
99 struct backlight_device
*bd
;
100 struct fb_event
*evdata
= data
;
101 int node
= evdata
->info
->node
;
104 /* If we aren't interested in this event, skip it immediately ... */
105 if (event
!= FB_EVENT_BLANK
)
108 bd
= container_of(self
, struct backlight_device
, fb_notif
);
109 mutex_lock(&bd
->ops_lock
);
113 if (bd
->ops
->check_fb
&& !bd
->ops
->check_fb(bd
, evdata
->info
))
116 fb_blank
= *(int *)evdata
->data
;
117 if (fb_blank
== FB_BLANK_UNBLANK
&& !bd
->fb_bl_on
[node
]) {
118 bd
->fb_bl_on
[node
] = true;
119 if (!bd
->use_count
++) {
120 bd
->props
.state
&= ~BL_CORE_FBBLANK
;
121 bd
->props
.fb_blank
= FB_BLANK_UNBLANK
;
122 backlight_update_status(bd
);
124 } else if (fb_blank
!= FB_BLANK_UNBLANK
&& bd
->fb_bl_on
[node
]) {
125 bd
->fb_bl_on
[node
] = false;
126 if (!(--bd
->use_count
)) {
127 bd
->props
.state
|= BL_CORE_FBBLANK
;
128 bd
->props
.fb_blank
= fb_blank
;
129 backlight_update_status(bd
);
133 mutex_unlock(&bd
->ops_lock
);
137 static int backlight_register_fb(struct backlight_device
*bd
)
139 memset(&bd
->fb_notif
, 0, sizeof(bd
->fb_notif
));
140 bd
->fb_notif
.notifier_call
= fb_notifier_callback
;
142 return fb_register_client(&bd
->fb_notif
);
145 static void backlight_unregister_fb(struct backlight_device
*bd
)
147 fb_unregister_client(&bd
->fb_notif
);
150 static inline int backlight_register_fb(struct backlight_device
*bd
)
155 static inline void backlight_unregister_fb(struct backlight_device
*bd
)
158 #endif /* CONFIG_FB */
160 static void backlight_generate_event(struct backlight_device
*bd
,
161 enum backlight_update_reason reason
)
166 case BACKLIGHT_UPDATE_SYSFS
:
167 envp
[0] = "SOURCE=sysfs";
169 case BACKLIGHT_UPDATE_HOTKEY
:
170 envp
[0] = "SOURCE=hotkey";
173 envp
[0] = "SOURCE=unknown";
177 kobject_uevent_env(&bd
->dev
.kobj
, KOBJ_CHANGE
, envp
);
178 sysfs_notify(&bd
->dev
.kobj
, NULL
, "actual_brightness");
181 static ssize_t
bl_power_show(struct device
*dev
, struct device_attribute
*attr
,
184 struct backlight_device
*bd
= to_backlight_device(dev
);
186 return sprintf(buf
, "%d\n", bd
->props
.power
);
189 static ssize_t
bl_power_store(struct device
*dev
, struct device_attribute
*attr
,
190 const char *buf
, size_t count
)
193 struct backlight_device
*bd
= to_backlight_device(dev
);
194 unsigned long power
, old_power
;
196 rc
= kstrtoul(buf
, 0, &power
);
201 mutex_lock(&bd
->ops_lock
);
203 pr_debug("set power to %lu\n", power
);
204 if (bd
->props
.power
!= power
) {
205 old_power
= bd
->props
.power
;
206 bd
->props
.power
= power
;
207 rc
= backlight_update_status(bd
);
209 bd
->props
.power
= old_power
;
216 mutex_unlock(&bd
->ops_lock
);
220 static DEVICE_ATTR_RW(bl_power
);
222 static ssize_t
brightness_show(struct device
*dev
,
223 struct device_attribute
*attr
, char *buf
)
225 struct backlight_device
*bd
= to_backlight_device(dev
);
227 return sprintf(buf
, "%d\n", bd
->props
.brightness
);
230 int backlight_device_set_brightness(struct backlight_device
*bd
,
231 unsigned long brightness
)
235 mutex_lock(&bd
->ops_lock
);
237 if (brightness
> bd
->props
.max_brightness
)
240 pr_debug("set brightness to %lu\n", brightness
);
241 bd
->props
.brightness
= brightness
;
242 rc
= backlight_update_status(bd
);
245 mutex_unlock(&bd
->ops_lock
);
247 backlight_generate_event(bd
, BACKLIGHT_UPDATE_SYSFS
);
251 EXPORT_SYMBOL(backlight_device_set_brightness
);
253 static ssize_t
brightness_store(struct device
*dev
,
254 struct device_attribute
*attr
, const char *buf
, size_t count
)
257 struct backlight_device
*bd
= to_backlight_device(dev
);
258 unsigned long brightness
;
260 rc
= kstrtoul(buf
, 0, &brightness
);
264 rc
= backlight_device_set_brightness(bd
, brightness
);
266 return rc
? rc
: count
;
268 static DEVICE_ATTR_RW(brightness
);
270 static ssize_t
type_show(struct device
*dev
, struct device_attribute
*attr
,
273 struct backlight_device
*bd
= to_backlight_device(dev
);
275 return sprintf(buf
, "%s\n", backlight_types
[bd
->props
.type
]);
277 static DEVICE_ATTR_RO(type
);
279 static ssize_t
max_brightness_show(struct device
*dev
,
280 struct device_attribute
*attr
, char *buf
)
282 struct backlight_device
*bd
= to_backlight_device(dev
);
284 return sprintf(buf
, "%d\n", bd
->props
.max_brightness
);
286 static DEVICE_ATTR_RO(max_brightness
);
288 static ssize_t
actual_brightness_show(struct device
*dev
,
289 struct device_attribute
*attr
, char *buf
)
292 struct backlight_device
*bd
= to_backlight_device(dev
);
294 mutex_lock(&bd
->ops_lock
);
295 if (bd
->ops
&& bd
->ops
->get_brightness
)
296 rc
= sprintf(buf
, "%d\n", bd
->ops
->get_brightness(bd
));
298 rc
= sprintf(buf
, "%d\n", bd
->props
.brightness
);
299 mutex_unlock(&bd
->ops_lock
);
303 static DEVICE_ATTR_RO(actual_brightness
);
305 static ssize_t
scale_show(struct device
*dev
,
306 struct device_attribute
*attr
, char *buf
)
308 struct backlight_device
*bd
= to_backlight_device(dev
);
310 if (WARN_ON(bd
->props
.scale
> BACKLIGHT_SCALE_NON_LINEAR
))
311 return sprintf(buf
, "unknown\n");
313 return sprintf(buf
, "%s\n", backlight_scale_types
[bd
->props
.scale
]);
315 static DEVICE_ATTR_RO(scale
);
317 static struct class *backlight_class
;
319 #ifdef CONFIG_PM_SLEEP
320 static int backlight_suspend(struct device
*dev
)
322 struct backlight_device
*bd
= to_backlight_device(dev
);
324 mutex_lock(&bd
->ops_lock
);
325 if (bd
->ops
&& bd
->ops
->options
& BL_CORE_SUSPENDRESUME
) {
326 bd
->props
.state
|= BL_CORE_SUSPENDED
;
327 backlight_update_status(bd
);
329 mutex_unlock(&bd
->ops_lock
);
334 static int backlight_resume(struct device
*dev
)
336 struct backlight_device
*bd
= to_backlight_device(dev
);
338 mutex_lock(&bd
->ops_lock
);
339 if (bd
->ops
&& bd
->ops
->options
& BL_CORE_SUSPENDRESUME
) {
340 bd
->props
.state
&= ~BL_CORE_SUSPENDED
;
341 backlight_update_status(bd
);
343 mutex_unlock(&bd
->ops_lock
);
349 static SIMPLE_DEV_PM_OPS(backlight_class_dev_pm_ops
, backlight_suspend
,
352 static void bl_device_release(struct device
*dev
)
354 struct backlight_device
*bd
= to_backlight_device(dev
);
358 static struct attribute
*bl_device_attrs
[] = {
359 &dev_attr_bl_power
.attr
,
360 &dev_attr_brightness
.attr
,
361 &dev_attr_actual_brightness
.attr
,
362 &dev_attr_max_brightness
.attr
,
363 &dev_attr_scale
.attr
,
367 ATTRIBUTE_GROUPS(bl_device
);
370 * backlight_force_update - tell the backlight subsystem that hardware state
372 * @bd: the backlight device to update
373 * @reason: reason for 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,
378 * a hot-key. The updated brightness is read using get_brightness() and the
379 * brightness value is reported using an uevent.
381 void backlight_force_update(struct backlight_device
*bd
,
382 enum backlight_update_reason reason
)
384 mutex_lock(&bd
->ops_lock
);
385 if (bd
->ops
&& bd
->ops
->get_brightness
)
386 bd
->props
.brightness
= bd
->ops
->get_brightness(bd
);
387 mutex_unlock(&bd
->ops_lock
);
388 backlight_generate_event(bd
, reason
);
390 EXPORT_SYMBOL(backlight_force_update
);
392 /* deprecated - use devm_backlight_device_register() */
393 struct backlight_device
*backlight_device_register(const char *name
,
394 struct device
*parent
, void *devdata
, const struct backlight_ops
*ops
,
395 const struct backlight_properties
*props
)
397 struct backlight_device
*new_bd
;
400 pr_debug("backlight_device_register: name=%s\n", name
);
402 new_bd
= kzalloc(sizeof(struct backlight_device
), GFP_KERNEL
);
404 return ERR_PTR(-ENOMEM
);
406 mutex_init(&new_bd
->update_lock
);
407 mutex_init(&new_bd
->ops_lock
);
409 new_bd
->dev
.class = backlight_class
;
410 new_bd
->dev
.parent
= parent
;
411 new_bd
->dev
.release
= bl_device_release
;
412 dev_set_name(&new_bd
->dev
, "%s", name
);
413 dev_set_drvdata(&new_bd
->dev
, devdata
);
415 /* Set default properties */
417 memcpy(&new_bd
->props
, props
,
418 sizeof(struct backlight_properties
));
419 if (props
->type
<= 0 || props
->type
>= BACKLIGHT_TYPE_MAX
) {
420 WARN(1, "%s: invalid backlight type", name
);
421 new_bd
->props
.type
= BACKLIGHT_RAW
;
424 new_bd
->props
.type
= BACKLIGHT_RAW
;
427 rc
= device_register(&new_bd
->dev
);
429 put_device(&new_bd
->dev
);
433 rc
= backlight_register_fb(new_bd
);
435 device_unregister(&new_bd
->dev
);
441 #ifdef CONFIG_PMAC_BACKLIGHT
442 mutex_lock(&pmac_backlight_mutex
);
444 pmac_backlight
= new_bd
;
445 mutex_unlock(&pmac_backlight_mutex
);
448 mutex_lock(&backlight_dev_list_mutex
);
449 list_add(&new_bd
->entry
, &backlight_dev_list
);
450 mutex_unlock(&backlight_dev_list_mutex
);
452 blocking_notifier_call_chain(&backlight_notifier
,
453 BACKLIGHT_REGISTERED
, new_bd
);
457 EXPORT_SYMBOL(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.
468 struct backlight_device
*backlight_device_get_by_type(enum backlight_type type
)
471 struct backlight_device
*bd
;
473 mutex_lock(&backlight_dev_list_mutex
);
474 list_for_each_entry(bd
, &backlight_dev_list
, entry
) {
475 if (bd
->props
.type
== type
) {
480 mutex_unlock(&backlight_dev_list_mutex
);
482 return found
? bd
: NULL
;
484 EXPORT_SYMBOL(backlight_device_get_by_type
);
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
492 * reference by calling backlight_put().
495 * A pointer to the backlight device if found, otherwise NULL.
497 struct backlight_device
*backlight_device_get_by_name(const char *name
)
501 dev
= class_find_device_by_name(backlight_class
, name
);
503 return dev
? to_backlight_device(dev
) : NULL
;
505 EXPORT_SYMBOL(backlight_device_get_by_name
);
507 /* deprecated - use devm_backlight_device_unregister() */
508 void backlight_device_unregister(struct backlight_device
*bd
)
513 mutex_lock(&backlight_dev_list_mutex
);
514 list_del(&bd
->entry
);
515 mutex_unlock(&backlight_dev_list_mutex
);
517 #ifdef CONFIG_PMAC_BACKLIGHT
518 mutex_lock(&pmac_backlight_mutex
);
519 if (pmac_backlight
== bd
)
520 pmac_backlight
= NULL
;
521 mutex_unlock(&pmac_backlight_mutex
);
524 blocking_notifier_call_chain(&backlight_notifier
,
525 BACKLIGHT_UNREGISTERED
, bd
);
527 mutex_lock(&bd
->ops_lock
);
529 mutex_unlock(&bd
->ops_lock
);
531 backlight_unregister_fb(bd
);
532 device_unregister(&bd
->dev
);
534 EXPORT_SYMBOL(backlight_device_unregister
);
536 static void devm_backlight_device_release(struct device
*dev
, void *res
)
538 struct backlight_device
*backlight
= *(struct backlight_device
**)res
;
540 backlight_device_unregister(backlight
);
543 static int devm_backlight_device_match(struct device
*dev
, void *res
,
546 struct backlight_device
**r
= res
;
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
560 * 0 on success, otherwise a negative error code
562 int backlight_register_notifier(struct notifier_block
*nb
)
564 return blocking_notifier_chain_register(&backlight_notifier
, nb
);
566 EXPORT_SYMBOL(backlight_register_notifier
);
569 * backlight_unregister_notifier - unregister a backlight notifier
570 * @nb: notifier block to unregister
572 * Register a notifier to get notified when backlight devices get registered
577 * 0 on success, otherwise a negative error code
579 int backlight_unregister_notifier(struct notifier_block
*nb
)
581 return blocking_notifier_chain_unregister(&backlight_notifier
, nb
);
583 EXPORT_SYMBOL(backlight_unregister_notifier
);
586 * devm_backlight_device_register - register a new backlight device
587 * @dev: the device to register
588 * @name: the name of the device
589 * @parent: a pointer to the parent device (often the same as @dev)
590 * @devdata: an optional pointer to be stored for private driver use
591 * @ops: the backlight operations structure
592 * @props: the backlight properties
594 * Creates and registers new backlight device. When a backlight device
595 * is registered the configuration must be specified in the @props
596 * parameter. See description of &backlight_properties.
600 * struct backlight on success, or an ERR_PTR on error
602 struct backlight_device
*devm_backlight_device_register(struct device
*dev
,
603 const char *name
, struct device
*parent
, void *devdata
,
604 const struct backlight_ops
*ops
,
605 const struct backlight_properties
*props
)
607 struct backlight_device
**ptr
, *backlight
;
609 ptr
= devres_alloc(devm_backlight_device_release
, sizeof(*ptr
),
612 return ERR_PTR(-ENOMEM
);
614 backlight
= backlight_device_register(name
, parent
, devdata
, ops
,
616 if (!IS_ERR(backlight
)) {
618 devres_add(dev
, ptr
);
625 EXPORT_SYMBOL(devm_backlight_device_register
);
628 * devm_backlight_device_unregister - unregister backlight device
629 * @dev: the device to unregister
630 * @bd: the backlight device to unregister
632 * Deallocates a backlight allocated with devm_backlight_device_register().
633 * Normally this function will not need to be called and the resource management
634 * code will ensure that the resources are freed.
636 void devm_backlight_device_unregister(struct device
*dev
,
637 struct backlight_device
*bd
)
641 rc
= devres_release(dev
, devm_backlight_device_release
,
642 devm_backlight_device_match
, bd
);
645 EXPORT_SYMBOL(devm_backlight_device_unregister
);
648 static int of_parent_match(struct device
*dev
, const void *data
)
650 return dev
->parent
&& dev
->parent
->of_node
== data
;
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
662 * caller's responsibility to drop the reference by calling put_device() on
663 * the backlight device's .dev field.
665 struct backlight_device
*of_find_backlight_by_node(struct device_node
*node
)
669 dev
= class_find_device(backlight_class
, NULL
, node
, of_parent_match
);
671 return dev
? to_backlight_device(dev
) : NULL
;
673 EXPORT_SYMBOL(of_find_backlight_by_node
);
676 static struct backlight_device
*of_find_backlight(struct device
*dev
)
678 struct backlight_device
*bd
= NULL
;
679 struct device_node
*np
;
684 if (IS_ENABLED(CONFIG_OF
) && dev
->of_node
) {
685 np
= of_parse_phandle(dev
->of_node
, "backlight", 0);
687 bd
= of_find_backlight_by_node(np
);
690 return ERR_PTR(-EPROBE_DEFER
);
692 * Note: gpio_backlight uses brightness as
693 * power state during probe
695 if (!bd
->props
.brightness
)
696 bd
->props
.brightness
= bd
->props
.max_brightness
;
703 static void devm_backlight_release(void *data
)
705 struct backlight_device
*bd
= data
;
708 put_device(&bd
->dev
);
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
718 * dropped on driver detach.
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.
726 struct backlight_device
*devm_of_find_backlight(struct device
*dev
)
728 struct backlight_device
*bd
;
731 bd
= of_find_backlight(dev
);
732 if (IS_ERR_OR_NULL(bd
))
734 ret
= devm_add_action(dev
, devm_backlight_release
, bd
);
736 put_device(&bd
->dev
);
741 EXPORT_SYMBOL(devm_of_find_backlight
);
743 static void __exit
backlight_class_exit(void)
745 class_destroy(backlight_class
);
748 static int __init
backlight_class_init(void)
750 backlight_class
= class_create(THIS_MODULE
, "backlight");
751 if (IS_ERR(backlight_class
)) {
752 pr_warn("Unable to create backlight class; errno = %ld\n",
753 PTR_ERR(backlight_class
));
754 return PTR_ERR(backlight_class
);
757 backlight_class
->dev_groups
= bl_device_groups
;
758 backlight_class
->pm
= &backlight_class_dev_pm_ops
;
759 INIT_LIST_HEAD(&backlight_dev_list
);
760 mutex_init(&backlight_dev_list_mutex
);
761 BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier
);
767 * if this is compiled into the kernel, we need to ensure that the
768 * class is registered before users of the class try to register lcd's
770 postcore_initcall(backlight_class_init
);
771 module_exit(backlight_class_exit
);
773 MODULE_LICENSE("GPL");
774 MODULE_AUTHOR("Jamey Hicks <jamey.hicks@hp.com>, Andrew Zabolotny <zap@homelink.ru>");
775 MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");