include/linux/backlight.h

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