1 /* SPDX-License-Identifier: GPL-2.0 */
3 * Backlight Lowlevel Control Abstraction
5 * Copyright (C) 2003,2004 Hewlett-Packard Company
9 #ifndef _LINUX_BACKLIGHT_H
10 #define _LINUX_BACKLIGHT_H
12 #include <linux/device.h>
14 #include <linux/mutex.h>
15 #include <linux/notifier.h>
18 * enum backlight_update_reason - what method was used to update backlight
20 * A driver indicates the method (reason) used for updating the backlight
21 * when calling backlight_force_update().
23 enum backlight_update_reason
{
25 * @BACKLIGHT_UPDATE_HOTKEY: The backlight was updated using a hot-key.
27 BACKLIGHT_UPDATE_HOTKEY
,
30 * @BACKLIGHT_UPDATE_SYSFS: The backlight was updated using sysfs.
32 BACKLIGHT_UPDATE_SYSFS
,
36 * enum backlight_type - the type of backlight control
38 * The type of interface used to control the backlight.
44 * The backlight is controlled using hardware registers.
49 * @BACKLIGHT_PLATFORM:
51 * The backlight is controlled using a platform-specific interface.
56 * @BACKLIGHT_FIRMWARE:
58 * The backlight is controlled using a standard firmware interface.
63 * @BACKLIGHT_TYPE_MAX: Number of entries.
69 * enum backlight_notification - the type of notification
71 * The notifications that is used for notification sent to the receiver
72 * that registered notifications using backlight_register_notifier().
74 enum backlight_notification
{
76 * @BACKLIGHT_REGISTERED: The backlight device is registered.
81 * @BACKLIGHT_UNREGISTERED: The backlight revice is unregistered.
83 BACKLIGHT_UNREGISTERED
,
86 /** enum backlight_scale - the type of scale used for brightness values
88 * The type of scale used for brightness values.
90 enum backlight_scale
{
92 * @BACKLIGHT_SCALE_UNKNOWN: The scale is unknown.
94 BACKLIGHT_SCALE_UNKNOWN
= 0,
97 * @BACKLIGHT_SCALE_LINEAR: The scale is linear.
99 * The linear scale will increase brightness the same for each step.
101 BACKLIGHT_SCALE_LINEAR
,
104 * @BACKLIGHT_SCALE_NON_LINEAR: The scale is not linear.
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.
109 BACKLIGHT_SCALE_NON_LINEAR
,
112 struct backlight_device
;
116 * struct backlight_ops - backlight operations
118 * The backlight operations are specified when the backlight device is registered.
120 struct backlight_ops
{
122 * @options: Configure how operations are called from the core.
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.
128 unsigned int options
;
130 #define BL_CORE_SUSPENDRESUME (1 << 0)
133 * @update_status: Operation called when properties have changed.
135 * Notify the backlight driver some property has changed.
136 * The update_status operation is protected by the update_lock.
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.
144 * 0 on success, negative error code if any failure occurred.
146 int (*update_status
)(struct backlight_device
*);
149 * @get_brightness: Return the current backlight brightness.
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.
157 * A brightness value which is 0 or a positive number.
158 * On failure a negative error code is returned.
160 int (*get_brightness
)(struct backlight_device
*);
163 * @check_fb: Check the framebuffer device.
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.
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.
174 int (*check_fb
)(struct backlight_device
*bd
, struct fb_info
*info
);
178 * struct backlight_properties - backlight properties
180 * This structure defines all the properties of a backlight.
182 struct backlight_properties
{
184 * @brightness: The current brightness requested by the user.
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.
190 * This value can be set in the backlight_properties passed
191 * to devm_backlight_device_register() to set a default brightness
197 * @max_brightness: The maximum brightness value.
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.
206 * @power: The current power mode.
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.
212 * The possible values are: (0: full on, 1 to 3: power saving
213 * modes; 4: full off), see FB_BLANK_XXX.
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.
222 * @fb_blank: The power state from the FBIOBLANK ioctl.
224 * When the FBIOBLANK ioctl is called @fb_blank is set to the
225 * blank parameter and the update_status() operation is called.
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.
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
236 * fb_blank is deprecated and will be removed.
241 * @type: The type of backlight supported.
243 * The backlight type allows userspace to make appropriate
244 * policy decisions based on the backlight type.
246 * This value must be set in the backlight_properties
247 * passed to devm_backlight_device_register().
249 enum backlight_type type
;
252 * @state: The state of the backlight core.
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.
258 * backlight drivers are expected to use backlight_is_blank()
259 * in their update_status() operation rather than reading the
262 * The state is maintained by the core and drivers may not modify it.
266 #define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
267 #define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */
270 * @scale: The type of the brightness scale.
272 enum backlight_scale scale
;
276 * struct backlight_device - backlight device data
278 * This structure holds all data required by a backlight device.
280 struct backlight_device
{
282 * @props: Backlight properties
284 struct backlight_properties props
;
287 * @update_lock: The lock used when calling the update_status() operation.
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.
294 struct mutex update_lock
;
297 * @ops_lock: The lock used around everything related to backlight_ops.
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.
303 struct mutex ops_lock
;
306 * @ops: Pointer to the backlight operations.
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.
312 const struct backlight_ops
*ops
;
315 * @fb_notif: The framebuffer notifier block
317 struct notifier_block fb_notif
;
320 * @entry: List entry of all registered backlight devices
322 struct list_head entry
;
325 * @dev: Parent device.
330 * @fb_bl_on: The state of individual fbdev's.
332 * Multiple fbdev's may share one backlight device. The fb_bl_on
333 * records the state of the individual fbdev.
335 bool fb_bl_on
[FB_MAX
];
338 * @use_count: The number of uses of fb_bl_on.
344 * backlight_update_status - force an update of the backlight device status
345 * @bd: the backlight device
347 static inline int backlight_update_status(struct backlight_device
*bd
)
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
);
360 * backlight_enable - Enable backlight
361 * @bd: the backlight device to enable
363 static inline int backlight_enable(struct backlight_device
*bd
)
368 bd
->props
.power
= FB_BLANK_UNBLANK
;
369 bd
->props
.fb_blank
= FB_BLANK_UNBLANK
;
370 bd
->props
.state
&= ~BL_CORE_FBBLANK
;
372 return backlight_update_status(bd
);
376 * backlight_disable - Disable backlight
377 * @bd: the backlight device to disable
379 static inline int backlight_disable(struct backlight_device
*bd
)
384 bd
->props
.power
= FB_BLANK_POWERDOWN
;
385 bd
->props
.fb_blank
= FB_BLANK_POWERDOWN
;
386 bd
->props
.state
|= BL_CORE_FBBLANK
;
388 return backlight_update_status(bd
);
392 * backlight_is_blank - Return true if display is expected to be blank
393 * @bd: the backlight device
395 * Display is expected to be blank if any of these is true::
397 * 1) if power in not UNBLANK
398 * 2) if fb_blank is not UNBLANK
399 * 3) if state indicate BLANK or SUSPENDED
401 * Returns true if display is expected to be blank, false otherwise.
403 static inline bool backlight_is_blank(const struct backlight_device
*bd
)
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
);
411 * backlight_get_brightness - Returns the current brightness value
412 * @bd: the backlight device
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.
418 * Backlight drivers are expected to use this function in their update_status()
419 * operation to get the brightness value.
421 static inline int backlight_get_brightness(const struct backlight_device
*bd
)
423 if (backlight_is_blank(bd
))
426 return bd
->props
.brightness
;
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
);
450 #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
453 * bl_get_data - access devdata
454 * @bl_dev: pointer to backlight device
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
462 * pointer to devdata stored while registering the backlight device.
464 static inline void * bl_get_data(struct backlight_device
*bl_dev
)
466 return dev_get_drvdata(&bl_dev
->dev
);
470 struct backlight_device
*of_find_backlight_by_node(struct device_node
*node
);
472 static inline struct backlight_device
*
473 of_find_backlight_by_node(struct device_node
*node
)
479 #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
480 struct backlight_device
*devm_of_find_backlight(struct device
*dev
);
482 static inline struct backlight_device
*
483 devm_of_find_backlight(struct device
*dev
)