xref: /openbmc/linux/include/linux/backlight.h (revision b6539a11)
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  */
23 enum 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  */
40 enum 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  */
74 enum 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  */
90 enum 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 
112 struct backlight_device;
113 struct fb_info;
114 
115 /**
116  * struct backlight_ops - backlight operations
117  *
118  * The backlight operations are specified when the backlight device is registered.
119  */
120 struct 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  */
182 struct 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  */
280 struct 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  */
backlight_update_status(struct backlight_device * bd)347 static 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(&bd->update_lock);
355 
356 	return ret;
357 }
358 
359 /**
360  * backlight_enable - Enable backlight
361  * @bd: the backlight device to enable
362  */
backlight_enable(struct backlight_device * bd)363 static 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  */
backlight_disable(struct backlight_device * bd)379 static 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  */
backlight_is_blank(const struct backlight_device * bd)403 static 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  */
backlight_get_brightness(const struct backlight_device * bd)421 static 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 
429 struct backlight_device *
430 backlight_device_register(const char *name, struct device *dev, void *devdata,
431 			  const struct backlight_ops *ops,
432 			  const struct backlight_properties *props);
433 struct backlight_device *
434 devm_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);
438 void backlight_device_unregister(struct backlight_device *bd);
439 void devm_backlight_device_unregister(struct device *dev,
440 				      struct backlight_device *bd);
441 void backlight_force_update(struct backlight_device *bd,
442 			    enum backlight_update_reason reason);
443 int backlight_register_notifier(struct notifier_block *nb);
444 int backlight_unregister_notifier(struct notifier_block *nb);
445 struct backlight_device *backlight_device_get_by_name(const char *name);
446 struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
447 int 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  */
bl_get_data(struct backlight_device * bl_dev)464 static inline void * bl_get_data(struct backlight_device *bl_dev)
465 {
466 	return dev_get_drvdata(&bl_dev->dev);
467 }
468 
469 #ifdef CONFIG_OF
470 struct backlight_device *of_find_backlight_by_node(struct device_node *node);
471 #else
472 static inline struct backlight_device *
of_find_backlight_by_node(struct device_node * node)473 of_find_backlight_by_node(struct device_node *node)
474 {
475 	return NULL;
476 }
477 #endif
478 
479 #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
480 struct backlight_device *devm_of_find_backlight(struct device *dev);
481 #else
482 static inline struct backlight_device *
devm_of_find_backlight(struct device * dev)483 devm_of_find_backlight(struct device *dev)
484 {
485 	return NULL;
486 }
487 #endif
488 
489 #endif
490