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/types.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/** enum backlight_scale - the type of scale used for brightness values
69 *
70 * The type of scale used for brightness values.
71 */
72enum backlight_scale {
73 /**
74 * @BACKLIGHT_SCALE_UNKNOWN: The scale is unknown.
75 */
76 BACKLIGHT_SCALE_UNKNOWN = 0,
77
78 /**
79 * @BACKLIGHT_SCALE_LINEAR: The scale is linear.
80 *
81 * The linear scale will increase brightness the same for each step.
82 */
83 BACKLIGHT_SCALE_LINEAR,
84
85 /**
86 * @BACKLIGHT_SCALE_NON_LINEAR: The scale is not linear.
87 *
88 * This is often used when the brightness values tries to adjust to
89 * the relative perception of the eye demanding a non-linear scale.
90 */
91 BACKLIGHT_SCALE_NON_LINEAR,
92};
93
94struct backlight_device;
95
96/**
97 * struct backlight_ops - backlight operations
98 *
99 * The backlight operations are specified when the backlight device is registered.
100 */
101struct backlight_ops {
102 /**
103 * @options: Configure how operations are called from the core.
104 *
105 * The options parameter is used to adjust the behaviour of the core.
106 * Set BL_CORE_SUSPENDRESUME to get the update_status() operation called
107 * upon suspend and resume.
108 */
109 unsigned int options;
110
111#define BL_CORE_SUSPENDRESUME (1 << 0)
112
113 /**
114 * @update_status: Operation called when properties have changed.
115 *
116 * Notify the backlight driver some property has changed.
117 * The update_status operation is protected by the update_lock.
118 *
119 * The backlight driver is expected to use backlight_is_blank()
120 * to check if the display is blanked and set brightness accordingly.
121 * update_status() is called when any of the properties has changed.
122 *
123 * RETURNS:
124 *
125 * 0 on success, negative error code if any failure occurred.
126 */
127 int (*update_status)(struct backlight_device *);
128
129 /**
130 * @get_brightness: Return the current backlight brightness.
131 *
132 * The driver may implement this as a readback from the HW.
133 * This operation is optional and if not present then the current
134 * brightness property value is used.
135 *
136 * RETURNS:
137 *
138 * A brightness value which is 0 or a positive number.
139 * On failure a negative error code is returned.
140 */
141 int (*get_brightness)(struct backlight_device *);
142
143 /**
144 * @controls_device: Check against the display device
145 *
146 * Check if the backlight controls the given display device. This
147 * operation is optional and if not implemented it is assumed that
148 * the display is always the one controlled by the backlight.
149 *
150 * RETURNS:
151 *
152 * If display_dev is NULL or display_dev matches the device controlled by
153 * the backlight, return true. Otherwise return false.
154 */
155 bool (*controls_device)(struct backlight_device *bd, struct device *display_dev);
156};
157
158/**
159 * struct backlight_properties - backlight properties
160 *
161 * This structure defines all the properties of a backlight.
162 */
163struct backlight_properties {
164 /**
165 * @brightness: The current brightness requested by the user.
166 *
167 * The backlight core makes sure the range is (0 to max_brightness)
168 * when the brightness is set via the sysfs attribute:
169 * /sys/class/backlight/<backlight>/brightness.
170 *
171 * This value can be set in the backlight_properties passed
172 * to devm_backlight_device_register() to set a default brightness
173 * value.
174 */
175 int brightness;
176
177 /**
178 * @max_brightness: The maximum brightness value.
179 *
180 * This value must be set in the backlight_properties passed to
181 * devm_backlight_device_register() and shall not be modified by the
182 * driver after registration.
183 */
184 int max_brightness;
185
186 /**
187 * @power: The current power mode.
188 *
189 * User space can configure the power mode using the sysfs
190 * attribute: /sys/class/backlight/<backlight>/bl_power
191 * When the power property is updated update_status() is called.
192 *
193 * The possible values are: (0: full on, 4: full off), see
194 * BACKLIGHT_POWER constants.
195 *
196 * When the backlight device is enabled, @power is set to
197 * BACKLIGHT_POWER_ON. When the backlight device is disabled,
198 * @power is set to BACKLIGHT_POWER_OFF.
199 */
200 int power;
201
202#define BACKLIGHT_POWER_ON (0)
203#define BACKLIGHT_POWER_OFF (4)
204#define BACKLIGHT_POWER_REDUCED (1) // deprecated; don't use in new code
205
206 /**
207 * @type: The type of backlight supported.
208 *
209 * The backlight type allows userspace to make appropriate
210 * policy decisions based on the backlight type.
211 *
212 * This value must be set in the backlight_properties
213 * passed to devm_backlight_device_register().
214 */
215 enum backlight_type type;
216
217 /**
218 * @state: The state of the backlight core.
219 *
220 * The state is a bitmask. BL_CORE_FBBLANK is set when the display
221 * is expected to be blank. BL_CORE_SUSPENDED is set when the
222 * driver is suspended.
223 *
224 * backlight drivers are expected to use backlight_is_blank()
225 * in their update_status() operation rather than reading the
226 * state property.
227 *
228 * The state is maintained by the core and drivers may not modify it.
229 */
230 unsigned int state;
231
232#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
233#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */
234
235 /**
236 * @scale: The type of the brightness scale.
237 */
238 enum backlight_scale scale;
239};
240
241/**
242 * struct backlight_device - backlight device data
243 *
244 * This structure holds all data required by a backlight device.
245 */
246struct backlight_device {
247 /**
248 * @props: Backlight properties
249 */
250 struct backlight_properties props;
251
252 /**
253 * @update_lock: The lock used when calling the update_status() operation.
254 *
255 * update_lock is an internal backlight lock that serialise access
256 * to the update_status() operation. The backlight core holds the update_lock
257 * when calling the update_status() operation. The update_lock shall not
258 * be used by backlight drivers.
259 */
260 struct mutex update_lock;
261
262 /**
263 * @ops_lock: The lock used around everything related to backlight_ops.
264 *
265 * ops_lock is an internal backlight lock that protects the ops pointer
266 * and is used around all accesses to ops and when the operations are
267 * invoked. The ops_lock shall not be used by backlight drivers.
268 */
269 struct mutex ops_lock;
270
271 /**
272 * @ops: Pointer to the backlight operations.
273 *
274 * If ops is NULL, the driver that registered this device has been unloaded,
275 * and if class_get_devdata() points to something in the body of that driver,
276 * it is also invalid.
277 */
278 const struct backlight_ops *ops;
279
280 /**
281 * @entry: List entry of all registered backlight devices
282 */
283 struct list_head entry;
284
285 /**
286 * @dev: Parent device.
287 */
288 struct device dev;
289
290 /**
291 * @use_count: The number of unblanked displays.
292 */
293 int use_count;
294};
295
296/**
297 * backlight_update_status - force an update of the backlight device status
298 * @bd: the backlight device
299 */
300static inline int backlight_update_status(struct backlight_device *bd)
301{
302 int ret = -ENOENT;
303
304 mutex_lock(&bd->update_lock);
305 if (bd->ops && bd->ops->update_status)
306 ret = bd->ops->update_status(bd);
307 mutex_unlock(lock: &bd->update_lock);
308
309 return ret;
310}
311
312/**
313 * backlight_enable - Enable backlight
314 * @bd: the backlight device to enable
315 */
316static inline int backlight_enable(struct backlight_device *bd)
317{
318 if (!bd)
319 return 0;
320
321 bd->props.power = BACKLIGHT_POWER_ON;
322 bd->props.state &= ~BL_CORE_FBBLANK;
323
324 return backlight_update_status(bd);
325}
326
327/**
328 * backlight_disable - Disable backlight
329 * @bd: the backlight device to disable
330 */
331static inline int backlight_disable(struct backlight_device *bd)
332{
333 if (!bd)
334 return 0;
335
336 bd->props.power = BACKLIGHT_POWER_OFF;
337 bd->props.state |= BL_CORE_FBBLANK;
338
339 return backlight_update_status(bd);
340}
341
342/**
343 * backlight_is_blank - Return true if display is expected to be blank
344 * @bd: the backlight device
345 *
346 * Display is expected to be blank if any of these is true::
347 *
348 * 1) if power in not UNBLANK
349 * 2) if state indicate BLANK or SUSPENDED
350 *
351 * Returns true if display is expected to be blank, false otherwise.
352 */
353static inline bool backlight_is_blank(const struct backlight_device *bd)
354{
355 return bd->props.power != BACKLIGHT_POWER_ON ||
356 bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK);
357}
358
359/**
360 * backlight_get_brightness - Returns the current brightness value
361 * @bd: the backlight device
362 *
363 * Returns the current brightness value, taking in consideration the current
364 * state. If backlight_is_blank() returns true then return 0 as brightness
365 * otherwise return the current brightness property value.
366 *
367 * Backlight drivers are expected to use this function in their update_status()
368 * operation to get the brightness value.
369 */
370static inline int backlight_get_brightness(const struct backlight_device *bd)
371{
372 if (backlight_is_blank(bd))
373 return 0;
374 else
375 return bd->props.brightness;
376}
377
378struct backlight_device *
379backlight_device_register(const char *name, struct device *dev, void *devdata,
380 const struct backlight_ops *ops,
381 const struct backlight_properties *props);
382struct backlight_device *
383devm_backlight_device_register(struct device *dev, const char *name,
384 struct device *parent, void *devdata,
385 const struct backlight_ops *ops,
386 const struct backlight_properties *props);
387void backlight_device_unregister(struct backlight_device *bd);
388void devm_backlight_device_unregister(struct device *dev,
389 struct backlight_device *bd);
390void backlight_force_update(struct backlight_device *bd,
391 enum backlight_update_reason reason);
392struct backlight_device *backlight_device_get_by_name(const char *name);
393struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
394int backlight_device_set_brightness(struct backlight_device *bd,
395 unsigned long brightness);
396
397#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
398void backlight_notify_blank(struct backlight_device *bd,
399 struct device *display_dev,
400 bool fb_on, bool prev_fb_on);
401void backlight_notify_blank_all(struct device *display_dev,
402 bool fb_on, bool prev_fb_on);
403#else
404static inline void backlight_notify_blank(struct backlight_device *bd,
405 struct device *display_dev,
406 bool fb_on, bool prev_fb_on)
407{ }
408static inline void backlight_notify_blank_all(struct device *display_dev,
409 bool fb_on, bool prev_fb_on)
410{ }
411#endif
412
413#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
414
415/**
416 * bl_get_data - access devdata
417 * @bl_dev: pointer to backlight device
418 *
419 * When a backlight device is registered the driver has the possibility
420 * to supply a void * devdata. bl_get_data() return a pointer to the
421 * devdata.
422 *
423 * RETURNS:
424 *
425 * pointer to devdata stored while registering the backlight device.
426 */
427static inline void * bl_get_data(struct backlight_device *bl_dev)
428{
429 return dev_get_drvdata(dev: &bl_dev->dev);
430}
431
432#ifdef CONFIG_OF
433struct backlight_device *of_find_backlight_by_node(struct device_node *node);
434#else
435static inline struct backlight_device *
436of_find_backlight_by_node(struct device_node *node)
437{
438 return NULL;
439}
440#endif
441
442#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
443struct backlight_device *devm_of_find_backlight(struct device *dev);
444#else
445static inline struct backlight_device *
446devm_of_find_backlight(struct device *dev)
447{
448 return NULL;
449}
450#endif
451
452#endif
453

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

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