1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Backlight Lowlevel Control Abstraction
4 *
5 * Copyright (C) 2003,2004 Hewlett-Packard Company
6 *
7 */
8
9#ifndef _LINUX_BACKLIGHT_H
10#define _LINUX_BACKLIGHT_H
11
12#include <linux/device.h>
13#include <linux/fb.h>
14#include <linux/mutex.h>
15#include <linux/notifier.h>
16
17/**
18 * enum backlight_update_reason - what method was used to update backlight
19 *
20 * A driver indicates the method (reason) used for updating the backlight
21 * when calling backlight_force_update().
22 */
23enum backlight_update_reason {
24 /**
25 * @BACKLIGHT_UPDATE_HOTKEY: The backlight was updated using a hot-key.
26 */
27 BACKLIGHT_UPDATE_HOTKEY,
28
29 /**
30 * @BACKLIGHT_UPDATE_SYSFS: The backlight was updated using sysfs.
31 */
32 BACKLIGHT_UPDATE_SYSFS,
33};
34
35/**
36 * enum backlight_type - the type of backlight control
37 *
38 * The type of interface used to control the backlight.
39 */
40enum backlight_type {
41 /**
42 * @BACKLIGHT_RAW:
43 *
44 * The backlight is controlled using hardware registers.
45 */
46 BACKLIGHT_RAW = 1,
47
48 /**
49 * @BACKLIGHT_PLATFORM:
50 *
51 * The backlight is controlled using a platform-specific interface.
52 */
53 BACKLIGHT_PLATFORM,
54
55 /**
56 * @BACKLIGHT_FIRMWARE:
57 *
58 * The backlight is controlled using a standard firmware interface.
59 */
60 BACKLIGHT_FIRMWARE,
61
62 /**
63 * @BACKLIGHT_TYPE_MAX: Number of entries.
64 */
65 BACKLIGHT_TYPE_MAX,
66};
67
68/**
69 * enum backlight_notification - the type of notification
70 *
71 * The notifications that is used for notification sent to the receiver
72 * that registered notifications using backlight_register_notifier().
73 */
74enum backlight_notification {
75 /**
76 * @BACKLIGHT_REGISTERED: The backlight device is registered.
77 */
78 BACKLIGHT_REGISTERED,
79
80 /**
81 * @BACKLIGHT_UNREGISTERED: The backlight revice is unregistered.
82 */
83 BACKLIGHT_UNREGISTERED,
84};
85
86/** enum backlight_scale - the type of scale used for brightness values
87 *
88 * The type of scale used for brightness values.
89 */
90enum backlight_scale {
91 /**
92 * @BACKLIGHT_SCALE_UNKNOWN: The scale is unknown.
93 */
94 BACKLIGHT_SCALE_UNKNOWN = 0,
95
96 /**
97 * @BACKLIGHT_SCALE_LINEAR: The scale is linear.
98 *
99 * The linear scale will increase brightness the same for each step.
100 */
101 BACKLIGHT_SCALE_LINEAR,
102
103 /**
104 * @BACKLIGHT_SCALE_NON_LINEAR: The scale is not linear.
105 *
106 * This is often used when the brightness values tries to adjust to
107 * the relative perception of the eye demanding a non-linear scale.
108 */
109 BACKLIGHT_SCALE_NON_LINEAR,
110};
111
112struct backlight_device;
113struct fb_info;
114
115/**
116 * struct backlight_ops - backlight operations
117 *
118 * The backlight operations are specified when the backlight device is registered.
119 */
120struct backlight_ops {
121 /**
122 * @options: Configure how operations are called from the core.
123 *
124 * The options parameter is used to adjust the behaviour of the core.
125 * Set BL_CORE_SUSPENDRESUME to get the update_status() operation called
126 * upon suspend and resume.
127 */
128 unsigned int options;
129
130#define BL_CORE_SUSPENDRESUME (1 << 0)
131
132 /**
133 * @update_status: Operation called when properties have changed.
134 *
135 * Notify the backlight driver some property has changed.
136 * The update_status operation is protected by the update_lock.
137 *
138 * The backlight driver is expected to use backlight_is_blank()
139 * to check if the display is blanked and set brightness accordingly.
140 * update_status() is called when any of the properties has changed.
141 *
142 * RETURNS:
143 *
144 * 0 on success, negative error code if any failure occurred.
145 */
146 int (*update_status)(struct backlight_device *);
147
148 /**
149 * @get_brightness: Return the current backlight brightness.
150 *
151 * The driver may implement this as a readback from the HW.
152 * This operation is optional and if not present then the current
153 * brightness property value is used.
154 *
155 * RETURNS:
156 *
157 * A brightness value which is 0 or a positive number.
158 * On failure a negative error code is returned.
159 */
160 int (*get_brightness)(struct backlight_device *);
161
162 /**
163 * @check_fb: Check the framebuffer device.
164 *
165 * Check if given framebuffer device is the one bound to this backlight.
166 * This operation is optional and if not implemented it is assumed that the
167 * fbdev is always the one bound to the backlight.
168 *
169 * RETURNS:
170 *
171 * If info is NULL or the info matches the fbdev bound to the backlight return true.
172 * If info does not match the fbdev bound to the backlight return false.
173 */
174 int (*check_fb)(struct backlight_device *bd, struct fb_info *info);
175};
176
177/**
178 * struct backlight_properties - backlight properties
179 *
180 * This structure defines all the properties of a backlight.
181 */
182struct backlight_properties {
183 /**
184 * @brightness: The current brightness requested by the user.
185 *
186 * The backlight core makes sure the range is (0 to max_brightness)
187 * when the brightness is set via the sysfs attribute:
188 * /sys/class/backlight/<backlight>/brightness.
189 *
190 * This value can be set in the backlight_properties passed
191 * to devm_backlight_device_register() to set a default brightness
192 * value.
193 */
194 int brightness;
195
196 /**
197 * @max_brightness: The maximum brightness value.
198 *
199 * This value must be set in the backlight_properties passed to
200 * devm_backlight_device_register() and shall not be modified by the
201 * driver after registration.
202 */
203 int max_brightness;
204
205 /**
206 * @power: The current power mode.
207 *
208 * User space can configure the power mode using the sysfs
209 * attribute: /sys/class/backlight/<backlight>/bl_power
210 * When the power property is updated update_status() is called.
211 *
212 * The possible values are: (0: full on, 1 to 3: power saving
213 * modes; 4: full off), see FB_BLANK_XXX.
214 *
215 * When the backlight device is enabled @power is set
216 * to FB_BLANK_UNBLANK. When the backlight device is disabled
217 * @power is set to FB_BLANK_POWERDOWN.
218 */
219 int power;
220
221 /**
222 * @fb_blank: The power state from the FBIOBLANK ioctl.
223 *
224 * When the FBIOBLANK ioctl is called @fb_blank is set to the
225 * blank parameter and the update_status() operation is called.
226 *
227 * When the backlight device is enabled @fb_blank is set
228 * to FB_BLANK_UNBLANK. When the backlight device is disabled
229 * @fb_blank is set to FB_BLANK_POWERDOWN.
230 *
231 * Backlight drivers should avoid using this property. It has been
232 * replaced by state & BL_CORE_FBLANK (although most drivers should
233 * use backlight_is_blank() as the preferred means to get the blank
234 * state).
235 *
236 * fb_blank is deprecated and will be removed.
237 */
238 int fb_blank;
239
240 /**
241 * @type: The type of backlight supported.
242 *
243 * The backlight type allows userspace to make appropriate
244 * policy decisions based on the backlight type.
245 *
246 * This value must be set in the backlight_properties
247 * passed to devm_backlight_device_register().
248 */
249 enum backlight_type type;
250
251 /**
252 * @state: The state of the backlight core.
253 *
254 * The state is a bitmask. BL_CORE_FBBLANK is set when the display
255 * is expected to be blank. BL_CORE_SUSPENDED is set when the
256 * driver is suspended.
257 *
258 * backlight drivers are expected to use backlight_is_blank()
259 * in their update_status() operation rather than reading the
260 * state property.
261 *
262 * The state is maintained by the core and drivers may not modify it.
263 */
264 unsigned int state;
265
266#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
267#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */
268
269 /**
270 * @scale: The type of the brightness scale.
271 */
272 enum backlight_scale scale;
273};
274
275/**
276 * struct backlight_device - backlight device data
277 *
278 * This structure holds all data required by a backlight device.
279 */
280struct backlight_device {
281 /**
282 * @props: Backlight properties
283 */
284 struct backlight_properties props;
285
286 /**
287 * @update_lock: The lock used when calling the update_status() operation.
288 *
289 * update_lock is an internal backlight lock that serialise access
290 * to the update_status() operation. The backlight core holds the update_lock
291 * when calling the update_status() operation. The update_lock shall not
292 * be used by backlight drivers.
293 */
294 struct mutex update_lock;
295
296 /**
297 * @ops_lock: The lock used around everything related to backlight_ops.
298 *
299 * ops_lock is an internal backlight lock that protects the ops pointer
300 * and is used around all accesses to ops and when the operations are
301 * invoked. The ops_lock shall not be used by backlight drivers.
302 */
303 struct mutex ops_lock;
304
305 /**
306 * @ops: Pointer to the backlight operations.
307 *
308 * If ops is NULL, the driver that registered this device has been unloaded,
309 * and if class_get_devdata() points to something in the body of that driver,
310 * it is also invalid.
311 */
312 const struct backlight_ops *ops;
313
314 /**
315 * @fb_notif: The framebuffer notifier block
316 */
317 struct notifier_block fb_notif;
318
319 /**
320 * @entry: List entry of all registered backlight devices
321 */
322 struct list_head entry;
323
324 /**
325 * @dev: Parent device.
326 */
327 struct device dev;
328
329 /**
330 * @fb_bl_on: The state of individual fbdev's.
331 *
332 * Multiple fbdev's may share one backlight device. The fb_bl_on
333 * records the state of the individual fbdev.
334 */
335 bool fb_bl_on[FB_MAX];
336
337 /**
338 * @use_count: The number of uses of fb_bl_on.
339 */
340 int use_count;
341};
342
343/**
344 * backlight_update_status - force an update of the backlight device status
345 * @bd: the backlight device
346 */
347static inline int backlight_update_status(struct backlight_device *bd)
348{
349 int ret = -ENOENT;
350
351 mutex_lock(&bd->update_lock);
352 if (bd->ops && bd->ops->update_status)
353 ret = bd->ops->update_status(bd);
354 mutex_unlock(lock: &bd->update_lock);
355
356 return ret;
357}
358
359/**
360 * backlight_enable - Enable backlight
361 * @bd: the backlight device to enable
362 */
363static inline int backlight_enable(struct backlight_device *bd)
364{
365 if (!bd)
366 return 0;
367
368 bd->props.power = FB_BLANK_UNBLANK;
369 bd->props.fb_blank = FB_BLANK_UNBLANK;
370 bd->props.state &= ~BL_CORE_FBBLANK;
371
372 return backlight_update_status(bd);
373}
374
375/**
376 * backlight_disable - Disable backlight
377 * @bd: the backlight device to disable
378 */
379static inline int backlight_disable(struct backlight_device *bd)
380{
381 if (!bd)
382 return 0;
383
384 bd->props.power = FB_BLANK_POWERDOWN;
385 bd->props.fb_blank = FB_BLANK_POWERDOWN;
386 bd->props.state |= BL_CORE_FBBLANK;
387
388 return backlight_update_status(bd);
389}
390
391/**
392 * backlight_is_blank - Return true if display is expected to be blank
393 * @bd: the backlight device
394 *
395 * Display is expected to be blank if any of these is true::
396 *
397 * 1) if power in not UNBLANK
398 * 2) if fb_blank is not UNBLANK
399 * 3) if state indicate BLANK or SUSPENDED
400 *
401 * Returns true if display is expected to be blank, false otherwise.
402 */
403static inline bool backlight_is_blank(const struct backlight_device *bd)
404{
405 return bd->props.power != FB_BLANK_UNBLANK ||
406 bd->props.fb_blank != FB_BLANK_UNBLANK ||
407 bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK);
408}
409
410/**
411 * backlight_get_brightness - Returns the current brightness value
412 * @bd: the backlight device
413 *
414 * Returns the current brightness value, taking in consideration the current
415 * state. If backlight_is_blank() returns true then return 0 as brightness
416 * otherwise return the current brightness property value.
417 *
418 * Backlight drivers are expected to use this function in their update_status()
419 * operation to get the brightness value.
420 */
421static inline int backlight_get_brightness(const struct backlight_device *bd)
422{
423 if (backlight_is_blank(bd))
424 return 0;
425 else
426 return bd->props.brightness;
427}
428
429struct backlight_device *
430backlight_device_register(const char *name, struct device *dev, void *devdata,
431 const struct backlight_ops *ops,
432 const struct backlight_properties *props);
433struct backlight_device *
434devm_backlight_device_register(struct device *dev, const char *name,
435 struct device *parent, void *devdata,
436 const struct backlight_ops *ops,
437 const struct backlight_properties *props);
438void backlight_device_unregister(struct backlight_device *bd);
439void devm_backlight_device_unregister(struct device *dev,
440 struct backlight_device *bd);
441void backlight_force_update(struct backlight_device *bd,
442 enum backlight_update_reason reason);
443int backlight_register_notifier(struct notifier_block *nb);
444int backlight_unregister_notifier(struct notifier_block *nb);
445struct backlight_device *backlight_device_get_by_name(const char *name);
446struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
447int backlight_device_set_brightness(struct backlight_device *bd,
448 unsigned long brightness);
449
450#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
451
452/**
453 * bl_get_data - access devdata
454 * @bl_dev: pointer to backlight device
455 *
456 * When a backlight device is registered the driver has the possibility
457 * to supply a void * devdata. bl_get_data() return a pointer to the
458 * devdata.
459 *
460 * RETURNS:
461 *
462 * pointer to devdata stored while registering the backlight device.
463 */
464static inline void * bl_get_data(struct backlight_device *bl_dev)
465{
466 return dev_get_drvdata(dev: &bl_dev->dev);
467}
468
469#ifdef CONFIG_OF
470struct backlight_device *of_find_backlight_by_node(struct device_node *node);
471#else
472static inline struct backlight_device *
473of_find_backlight_by_node(struct device_node *node)
474{
475 return NULL;
476}
477#endif
478
479#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
480struct backlight_device *devm_of_find_backlight(struct device *dev);
481#else
482static inline struct backlight_device *
483devm_of_find_backlight(struct device *dev)
484{
485 return NULL;
486}
487#endif
488
489#endif
490

source code of linux/include/linux/backlight.h