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);
697 static void devm_backlight_release(void *data)
699 struct backlight_device *bd = data;
702 put_device(&bd->dev);
706 * devm_of_find_backlight - find backlight for a device
709 * This function looks for a property named 'backlight' on the DT node
710 * connected to @dev and looks up the backlight device. The lookup is
711 * device managed so the reference to the backlight device is automatically
712 * dropped on driver detach.
716 * A pointer to the backlight device if found.
717 * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
718 * device is found. NULL if there's no backlight property.
720 struct backlight_device *devm_of_find_backlight(struct device *dev)
722 struct backlight_device *bd;
725 bd = of_find_backlight(dev);
726 if (IS_ERR_OR_NULL(bd))
728 ret = devm_add_action(dev, devm_backlight_release, bd);
730 put_device(&bd->dev);
735 EXPORT_SYMBOL(devm_of_find_backlight);
737 static void __exit backlight_class_exit(void)
739 class_destroy(backlight_class);
742 static int __init backlight_class_init(void)
744 backlight_class = class_create(THIS_MODULE, "backlight");
745 if (IS_ERR(backlight_class)) {
746 pr_warn("Unable to create backlight class; errno = %ld\n",
747 PTR_ERR(backlight_class));
748 return PTR_ERR(backlight_class);
751 backlight_class->dev_groups = bl_device_groups;
752 backlight_class->pm = &backlight_class_dev_pm_ops;
753 INIT_LIST_HEAD(&backlight_dev_list);
754 mutex_init(&backlight_dev_list_mutex);
755 BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
761 * if this is compiled into the kernel, we need to ensure that the
762 * class is registered before users of the class try to register lcd's
764 postcore_initcall(backlight_class_init);
765 module_exit(backlight_class_exit);
767 MODULE_LICENSE("GPL");
768 MODULE_AUTHOR("Jamey Hicks <jamey.hicks@hp.com>, Andrew Zabolotny <zap@homelink.ru>");
769 MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");