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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Backlight Lowlevel Control Abstraction
4 *
5 * Copyright (C) 2003,2004 Hewlett-Packard Company
6 *
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
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>
18#include <linux/slab.h>
19#include <linux/of.h>
20
21#ifdef CONFIG_PMAC_BACKLIGHT
22#include <asm/backlight.h>
23#endif
24
25/**
26 * DOC: overview
27 *
28 * The backlight core supports implementing backlight drivers.
29 *
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.
36 *
37 * Several sysfs attributes are provided by the backlight core::
38 *
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
42 *
43 * See Documentation/ABI/stable/sysfs-class-backlight for the full list.
44 *
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.
48 *
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.
53 *
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().
59 *
60 * Display drives can control the backlight device's status using
61 * backlight_notify_blank() and backlight_notify_blank_all(). If this
62 * results in a change in the backlight state the functions call the
63 * update_status() operation.
64 */
65
66static struct list_head backlight_dev_list;
67static struct mutex backlight_dev_list_mutex;
68
69static const char *const backlight_types[] = {
70 [BACKLIGHT_RAW] = "raw",
71 [BACKLIGHT_PLATFORM] = "platform",
72 [BACKLIGHT_FIRMWARE] = "firmware",
73};
74
75static const char *const backlight_scale_types[] = {
76 [BACKLIGHT_SCALE_UNKNOWN] = "unknown",
77 [BACKLIGHT_SCALE_LINEAR] = "linear",
78 [BACKLIGHT_SCALE_NON_LINEAR] = "non-linear",
79};
80
81void backlight_notify_blank(struct backlight_device *bd, struct device *display_dev,
82 bool fb_on, bool prev_fb_on)
83{
84 guard(mutex)(&bd->ops_lock);
85
86 if (!bd->ops)
87 return;
88 if (bd->ops->controls_device && !bd->ops->controls_device(bd, display_dev))
89 return;
90
91 if (fb_on && (!prev_fb_on || !bd->use_count)) {
92 if (!bd->use_count++) {
93 bd->props.state &= ~BL_CORE_FBBLANK;
94 backlight_update_status(bd);
95 }
96 } else if (!fb_on && prev_fb_on && bd->use_count) {
97 if (!(--bd->use_count)) {
98 bd->props.state |= BL_CORE_FBBLANK;
99 backlight_update_status(bd);
100 }
101 }
102}
103EXPORT_SYMBOL(backlight_notify_blank);
104
105void backlight_notify_blank_all(struct device *display_dev, bool fb_on, bool prev_fb_on)
106{
107 struct backlight_device *bd;
108
109 guard(mutex)(&backlight_dev_list_mutex);
110
111 list_for_each_entry(bd, &backlight_dev_list, entry)
112 backlight_notify_blank(bd, display_dev, fb_on, prev_fb_on);
113}
114EXPORT_SYMBOL(backlight_notify_blank_all);
115
116static void backlight_generate_event(struct backlight_device *bd,
117 enum backlight_update_reason reason)
118{
119 char *envp[2];
120
121 switch (reason) {
122 case BACKLIGHT_UPDATE_SYSFS:
123 envp[0] = "SOURCE=sysfs";
124 break;
125 case BACKLIGHT_UPDATE_HOTKEY:
126 envp[0] = "SOURCE=hotkey";
127 break;
128 default:
129 envp[0] = "SOURCE=unknown";
130 break;
131 }
132 envp[1] = NULL;
133 kobject_uevent_env(&bd->dev.kobj, KOBJ_CHANGE, envp);
134 sysfs_notify(&bd->dev.kobj, NULL, "actual_brightness");
135}
136
137static ssize_t bl_power_show(struct device *dev, struct device_attribute *attr,
138 char *buf)
139{
140 struct backlight_device *bd = to_backlight_device(dev);
141
142 return sysfs_emit(buf, "%d\n", bd->props.power);
143}
144
145static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr,
146 const char *buf, size_t count)
147{
148 int rc;
149 struct backlight_device *bd = to_backlight_device(dev);
150 unsigned long power, old_power;
151
152 rc = kstrtoul(buf, 0, &power);
153 if (rc)
154 return rc;
155
156 rc = -ENXIO;
157 mutex_lock(&bd->ops_lock);
158 if (bd->ops) {
159 pr_debug("set power to %lu\n", power);
160 if (bd->props.power != power) {
161 old_power = bd->props.power;
162 bd->props.power = power;
163 rc = backlight_update_status(bd);
164 if (rc)
165 bd->props.power = old_power;
166 else
167 rc = count;
168 } else {
169 rc = count;
170 }
171 }
172 mutex_unlock(&bd->ops_lock);
173
174 return rc;
175}
176static DEVICE_ATTR_RW(bl_power);
177
178static ssize_t brightness_show(struct device *dev,
179 struct device_attribute *attr, char *buf)
180{
181 struct backlight_device *bd = to_backlight_device(dev);
182
183 return sysfs_emit(buf, "%d\n", bd->props.brightness);
184}
185
186int backlight_device_set_brightness(struct backlight_device *bd,
187 unsigned long brightness)
188{
189 int rc = -ENXIO;
190
191 mutex_lock(&bd->ops_lock);
192 if (bd->ops) {
193 if (brightness > bd->props.max_brightness)
194 rc = -EINVAL;
195 else {
196 pr_debug("set brightness to %lu\n", brightness);
197 bd->props.brightness = brightness;
198 rc = backlight_update_status(bd);
199 }
200 }
201 mutex_unlock(&bd->ops_lock);
202
203 backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
204
205 return rc;
206}
207EXPORT_SYMBOL(backlight_device_set_brightness);
208
209static ssize_t brightness_store(struct device *dev,
210 struct device_attribute *attr, const char *buf, size_t count)
211{
212 int rc;
213 struct backlight_device *bd = to_backlight_device(dev);
214 unsigned long brightness;
215
216 rc = kstrtoul(buf, 0, &brightness);
217 if (rc)
218 return rc;
219
220 rc = backlight_device_set_brightness(bd, brightness);
221
222 return rc ? rc : count;
223}
224static DEVICE_ATTR_RW(brightness);
225
226static ssize_t type_show(struct device *dev, struct device_attribute *attr,
227 char *buf)
228{
229 struct backlight_device *bd = to_backlight_device(dev);
230
231 return sysfs_emit(buf, "%s\n", backlight_types[bd->props.type]);
232}
233static DEVICE_ATTR_RO(type);
234
235static ssize_t max_brightness_show(struct device *dev,
236 struct device_attribute *attr, char *buf)
237{
238 struct backlight_device *bd = to_backlight_device(dev);
239
240 return sysfs_emit(buf, "%d\n", bd->props.max_brightness);
241}
242static DEVICE_ATTR_RO(max_brightness);
243
244static ssize_t actual_brightness_show(struct device *dev,
245 struct device_attribute *attr, char *buf)
246{
247 int rc = -ENXIO;
248 struct backlight_device *bd = to_backlight_device(dev);
249
250 mutex_lock(&bd->ops_lock);
251 if (bd->ops && bd->ops->get_brightness) {
252 rc = bd->ops->get_brightness(bd);
253 if (rc >= 0)
254 rc = sysfs_emit(buf, "%d\n", rc);
255 } else {
256 rc = sysfs_emit(buf, "%d\n", bd->props.brightness);
257 }
258 mutex_unlock(&bd->ops_lock);
259
260 return rc;
261}
262static DEVICE_ATTR_RO(actual_brightness);
263
264static ssize_t scale_show(struct device *dev,
265 struct device_attribute *attr, char *buf)
266{
267 struct backlight_device *bd = to_backlight_device(dev);
268
269 if (WARN_ON(bd->props.scale > BACKLIGHT_SCALE_NON_LINEAR))
270 return sysfs_emit(buf, "unknown\n");
271
272 return sysfs_emit(buf, "%s\n", backlight_scale_types[bd->props.scale]);
273}
274static DEVICE_ATTR_RO(scale);
275
276#ifdef CONFIG_PM_SLEEP
277static int backlight_suspend(struct device *dev)
278{
279 struct backlight_device *bd = to_backlight_device(dev);
280
281 mutex_lock(&bd->ops_lock);
282 if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
283 bd->props.state |= BL_CORE_SUSPENDED;
284 backlight_update_status(bd);
285 }
286 mutex_unlock(&bd->ops_lock);
287
288 return 0;
289}
290
291static int backlight_resume(struct device *dev)
292{
293 struct backlight_device *bd = to_backlight_device(dev);
294
295 mutex_lock(&bd->ops_lock);
296 if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
297 bd->props.state &= ~BL_CORE_SUSPENDED;
298 backlight_update_status(bd);
299 }
300 mutex_unlock(&bd->ops_lock);
301
302 return 0;
303}
304#endif
305
306static SIMPLE_DEV_PM_OPS(backlight_class_dev_pm_ops, backlight_suspend,
307 backlight_resume);
308
309static void bl_device_release(struct device *dev)
310{
311 struct backlight_device *bd = to_backlight_device(dev);
312 kfree(bd);
313}
314
315static struct attribute *bl_device_attrs[] = {
316 &dev_attr_bl_power.attr,
317 &dev_attr_brightness.attr,
318 &dev_attr_actual_brightness.attr,
319 &dev_attr_max_brightness.attr,
320 &dev_attr_scale.attr,
321 &dev_attr_type.attr,
322 NULL,
323};
324ATTRIBUTE_GROUPS(bl_device);
325
326static const struct class backlight_class = {
327 .name = "backlight",
328 .dev_groups = bl_device_groups,
329 .pm = &backlight_class_dev_pm_ops,
330};
331
332/**
333 * backlight_force_update - tell the backlight subsystem that hardware state
334 * has changed
335 * @bd: the backlight device to update
336 * @reason: reason for update
337 *
338 * Updates the internal state of the backlight in response to a hardware event,
339 * and generates an uevent to notify userspace. A backlight driver shall call
340 * backlight_force_update() when the backlight is changed using, for example,
341 * a hot-key. The updated brightness is read using get_brightness() and the
342 * brightness value is reported using an uevent.
343 */
344void backlight_force_update(struct backlight_device *bd,
345 enum backlight_update_reason reason)
346{
347 int brightness;
348
349 mutex_lock(&bd->ops_lock);
350 if (bd->ops && bd->ops->get_brightness) {
351 brightness = bd->ops->get_brightness(bd);
352 if (brightness >= 0)
353 bd->props.brightness = brightness;
354 else
355 dev_err(&bd->dev,
356 "Could not update brightness from device: %pe\n",
357 ERR_PTR(brightness));
358 }
359 mutex_unlock(&bd->ops_lock);
360 backlight_generate_event(bd, reason);
361}
362EXPORT_SYMBOL(backlight_force_update);
363
364/* deprecated - use devm_backlight_device_register() */
365struct backlight_device *backlight_device_register(const char *name,
366 struct device *parent, void *devdata, const struct backlight_ops *ops,
367 const struct backlight_properties *props)
368{
369 struct backlight_device *new_bd;
370 int rc;
371
372 pr_debug("backlight_device_register: name=%s\n", name);
373
374 new_bd = kzalloc_obj(struct backlight_device);
375 if (!new_bd)
376 return ERR_PTR(-ENOMEM);
377
378 mutex_init(&new_bd->update_lock);
379 mutex_init(&new_bd->ops_lock);
380
381 new_bd->dev.class = &backlight_class;
382 new_bd->dev.parent = parent;
383 new_bd->dev.release = bl_device_release;
384 dev_set_name(&new_bd->dev, "%s", name);
385 dev_set_drvdata(&new_bd->dev, devdata);
386
387 /* Set default properties */
388 if (props) {
389 memcpy(&new_bd->props, props,
390 sizeof(struct backlight_properties));
391 if (props->type <= 0 || props->type >= BACKLIGHT_TYPE_MAX) {
392 WARN(1, "%s: invalid backlight type", name);
393 new_bd->props.type = BACKLIGHT_RAW;
394 }
395 } else {
396 new_bd->props.type = BACKLIGHT_RAW;
397 }
398
399 rc = device_register(&new_bd->dev);
400 if (rc) {
401 put_device(&new_bd->dev);
402 return ERR_PTR(rc);
403 }
404
405 new_bd->ops = ops;
406
407#ifdef CONFIG_PMAC_BACKLIGHT
408 mutex_lock(&pmac_backlight_mutex);
409 if (!pmac_backlight)
410 pmac_backlight = new_bd;
411 mutex_unlock(&pmac_backlight_mutex);
412#endif
413
414 mutex_lock(&backlight_dev_list_mutex);
415 list_add(&new_bd->entry, &backlight_dev_list);
416 mutex_unlock(&backlight_dev_list_mutex);
417
418 return new_bd;
419}
420EXPORT_SYMBOL(backlight_device_register);
421
422/** backlight_device_get_by_type - find first backlight device of a type
423 * @type: the type of backlight device
424 *
425 * Look up the first backlight device of the specified type
426 *
427 * RETURNS:
428 *
429 * Pointer to backlight device if any was found. Otherwise NULL.
430 */
431struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
432{
433 bool found = false;
434 struct backlight_device *bd;
435
436 mutex_lock(&backlight_dev_list_mutex);
437 list_for_each_entry(bd, &backlight_dev_list, entry) {
438 if (bd->props.type == type) {
439 found = true;
440 break;
441 }
442 }
443 mutex_unlock(&backlight_dev_list_mutex);
444
445 return found ? bd : NULL;
446}
447EXPORT_SYMBOL(backlight_device_get_by_type);
448
449/**
450 * backlight_device_get_by_name - Get backlight device by name
451 * @name: Device name
452 *
453 * This function looks up a backlight device by its name. It obtains a reference
454 * on the backlight device and it is the caller's responsibility to drop the
455 * reference by calling put_device().
456 *
457 * Returns:
458 * A pointer to the backlight device if found, otherwise NULL.
459 */
460struct backlight_device *backlight_device_get_by_name(const char *name)
461{
462 struct device *dev;
463
464 dev = class_find_device_by_name(&backlight_class, name);
465
466 return dev ? to_backlight_device(dev) : NULL;
467}
468EXPORT_SYMBOL(backlight_device_get_by_name);
469
470/* deprecated - use devm_backlight_device_unregister() */
471void backlight_device_unregister(struct backlight_device *bd)
472{
473 if (!bd)
474 return;
475
476 mutex_lock(&backlight_dev_list_mutex);
477 list_del(&bd->entry);
478 mutex_unlock(&backlight_dev_list_mutex);
479
480#ifdef CONFIG_PMAC_BACKLIGHT
481 mutex_lock(&pmac_backlight_mutex);
482 if (pmac_backlight == bd)
483 pmac_backlight = NULL;
484 mutex_unlock(&pmac_backlight_mutex);
485#endif
486
487 mutex_lock(&bd->ops_lock);
488 bd->ops = NULL;
489 mutex_unlock(&bd->ops_lock);
490
491 device_unregister(&bd->dev);
492}
493EXPORT_SYMBOL(backlight_device_unregister);
494
495static void devm_backlight_device_release(struct device *dev, void *res)
496{
497 struct backlight_device *backlight = *(struct backlight_device **)res;
498
499 backlight_device_unregister(backlight);
500}
501
502static int devm_backlight_device_match(struct device *dev, void *res,
503 void *data)
504{
505 struct backlight_device **r = res;
506
507 return *r == data;
508}
509
510/**
511 * devm_backlight_device_register - register a new backlight device
512 * @dev: the device to register
513 * @name: the name of the device
514 * @parent: a pointer to the parent device (often the same as @dev)
515 * @devdata: an optional pointer to be stored for private driver use
516 * @ops: the backlight operations structure
517 * @props: the backlight properties
518 *
519 * Creates and registers new backlight device. When a backlight device
520 * is registered the configuration must be specified in the @props
521 * parameter. See description of &backlight_properties.
522 *
523 * RETURNS:
524 *
525 * struct backlight on success, or an ERR_PTR on error
526 */
527struct backlight_device *devm_backlight_device_register(struct device *dev,
528 const char *name, struct device *parent, void *devdata,
529 const struct backlight_ops *ops,
530 const struct backlight_properties *props)
531{
532 struct backlight_device **ptr, *backlight;
533
534 ptr = devres_alloc(devm_backlight_device_release, sizeof(*ptr),
535 GFP_KERNEL);
536 if (!ptr)
537 return ERR_PTR(-ENOMEM);
538
539 backlight = backlight_device_register(name, parent, devdata, ops,
540 props);
541 if (!IS_ERR(backlight)) {
542 *ptr = backlight;
543 devres_add(dev, ptr);
544 } else {
545 devres_free(ptr);
546 }
547
548 return backlight;
549}
550EXPORT_SYMBOL(devm_backlight_device_register);
551
552/**
553 * devm_backlight_device_unregister - unregister backlight device
554 * @dev: the device to unregister
555 * @bd: the backlight device to unregister
556 *
557 * Deallocates a backlight allocated with devm_backlight_device_register().
558 * Normally this function will not need to be called and the resource management
559 * code will ensure that the resources are freed.
560 */
561void devm_backlight_device_unregister(struct device *dev,
562 struct backlight_device *bd)
563{
564 int rc;
565
566 rc = devres_release(dev, devm_backlight_device_release,
567 devm_backlight_device_match, bd);
568 WARN_ON(rc);
569}
570EXPORT_SYMBOL(devm_backlight_device_unregister);
571
572#ifdef CONFIG_OF
573static int of_parent_match(struct device *dev, const void *data)
574{
575 return dev->parent && dev->parent->of_node == data;
576}
577
578/**
579 * of_find_backlight_by_node() - find backlight device by device-tree node
580 * @node: device-tree node of the backlight device
581 *
582 * Returns a pointer to the backlight device corresponding to the given DT
583 * node or NULL if no such backlight device exists or if the device hasn't
584 * been probed yet.
585 *
586 * This function obtains a reference on the backlight device and it is the
587 * caller's responsibility to drop the reference by calling put_device() on
588 * the backlight device's .dev field.
589 */
590struct backlight_device *of_find_backlight_by_node(struct device_node *node)
591{
592 struct device *dev;
593
594 dev = class_find_device(&backlight_class, NULL, node, of_parent_match);
595
596 return dev ? to_backlight_device(dev) : NULL;
597}
598EXPORT_SYMBOL(of_find_backlight_by_node);
599#endif
600
601static struct backlight_device *of_find_backlight(struct device *dev)
602{
603 struct backlight_device *bd = NULL;
604 struct device_node *np;
605
606 if (!dev)
607 return NULL;
608
609 if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
610 np = of_parse_phandle(dev->of_node, "backlight", 0);
611 if (np) {
612 bd = of_find_backlight_by_node(np);
613 of_node_put(np);
614 if (!bd)
615 return ERR_PTR(-EPROBE_DEFER);
616 }
617 }
618
619 return bd;
620}
621
622static void devm_backlight_release(void *data)
623{
624 struct backlight_device *bd = data;
625
626 put_device(&bd->dev);
627}
628
629/**
630 * devm_of_find_backlight - find backlight for a device
631 * @dev: the device
632 *
633 * This function looks for a property named 'backlight' on the DT node
634 * connected to @dev and looks up the backlight device. The lookup is
635 * device managed so the reference to the backlight device is automatically
636 * dropped on driver detach.
637 *
638 * RETURNS:
639 *
640 * A pointer to the backlight device if found.
641 * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
642 * device is found. NULL if there's no backlight property.
643 */
644struct backlight_device *devm_of_find_backlight(struct device *dev)
645{
646 struct backlight_device *bd;
647 int ret;
648
649 bd = of_find_backlight(dev);
650 if (IS_ERR_OR_NULL(bd))
651 return bd;
652 ret = devm_add_action_or_reset(dev, devm_backlight_release, bd);
653 if (ret)
654 return ERR_PTR(ret);
655
656 return bd;
657}
658EXPORT_SYMBOL(devm_of_find_backlight);
659
660static void __exit backlight_class_exit(void)
661{
662 class_unregister(&backlight_class);
663}
664
665static int __init backlight_class_init(void)
666{
667 int ret;
668
669 ret = class_register(&backlight_class);
670 if (ret) {
671 pr_warn("Unable to create backlight class; errno = %d\n", ret);
672 return ret;
673 }
674
675 INIT_LIST_HEAD(&backlight_dev_list);
676 mutex_init(&backlight_dev_list_mutex);
677
678 return 0;
679}
680
681/*
682 * if this is compiled into the kernel, we need to ensure that the
683 * class is registered before users of the class try to register lcd's
684 */
685postcore_initcall(backlight_class_init);
686module_exit(backlight_class_exit);
687
688MODULE_LICENSE("GPL");
689MODULE_AUTHOR("Jamey Hicks <[email protected]>, Andrew Zabolotny <[email protected]>");
690MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");