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(&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(&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