#include <linux/mutex.h>
#include <linux/notifier.h>
-/* Notes on locking:
- *
- * backlight_device->ops_lock is an internal backlight lock protecting the
- * ops pointer and no code outside the core should need to touch it.
- *
- * Access to update_status() is serialised by the update_lock mutex since
- * most drivers seem to need this and historically get it wrong.
- *
- * Most drivers don't need locking on their get_brightness() method.
- * If yours does, you need to implement it in the driver. You can use the
- * update_lock mutex if appropriate.
- *
- * Any other use of the locks below is probably wrong.
- */
-
enum backlight_update_reason {
BACKLIGHT_UPDATE_HOTKEY,
BACKLIGHT_UPDATE_SYSFS,
struct backlight_device;
struct fb_info;
+/**
+ * struct backlight_ops - backlight operations
+ *
+ * The backlight operations are specified when the backlight device is registered.
+ */
struct backlight_ops {
+ /**
+ * @options: Configure how operations are called from the core.
+ *
+ * The options parameter is used to adjust the behaviour of the core.
+ * Set BL_CORE_SUSPENDRESUME to get the update_status() operation called
+ * upon suspend and resume.
+ */
unsigned int options;
#define BL_CORE_SUSPENDRESUME (1 << 0)
- /* Notify the backlight driver some property has changed */
+ /**
+ * @update_status: Operation called when properties have changed.
+ *
+ * Notify the backlight driver some property has changed.
+ * The update_status operation is protected by the update_lock.
+ *
+ * The backlight driver is expected to use backlight_is_blank()
+ * to check if the display is blanked and set brightness accordingly.
+ * update_status() is called when any of the properties has changed.
+ *
+ * RETURNS:
+ *
+ * 0 on success, negative error code if any failure occurred.
+ */
int (*update_status)(struct backlight_device *);
- /* Return the current backlight brightness (accounting for power,
- fb_blank etc.) */
+
+ /**
+ * @get_brightness: Return the current backlight brightness.
+ *
+ * The driver may implement this as a readback from the HW.
+ * This operation is optional and if not present then the current
+ * brightness property value is used.
+ *
+ * RETURNS:
+ *
+ * A brightness value which is 0 or a positive number.
+ * On failure a negative error code is returned.
+ */
int (*get_brightness)(struct backlight_device *);
- /* Check if given framebuffer device is the one bound to this backlight;
- return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */
- int (*check_fb)(struct backlight_device *, struct fb_info *);
+
+ /**
+ * @check_fb: Check the framebuffer device.
+ *
+ * Check if given framebuffer device is the one bound to this backlight.
+ * This operation is optional and if not implemented it is assumed that the
+ * fbdev is always the one bound to the backlight.
+ *
+ * RETURNS:
+ *
+ * If info is NULL or the info matches the fbdev bound to the backlight return true.
+ * If info does not match the fbdev bound to the backlight return false.
+ */
+ int (*check_fb)(struct backlight_device *bd, struct fb_info *info);
};
-/* This structure defines all the properties of a backlight */
+/**
+ * struct backlight_properties - backlight properties
+ *
+ * This structure defines all the properties of a backlight.
+ */
struct backlight_properties {
- /* Current User requested brightness (0 - max_brightness) */
+ /**
+ * @brightness: The current brightness requested by the user.
+ *
+ * The backlight core makes sure the range is (0 to max_brightness)
+ * when the brightness is set via the sysfs attribute:
+ * /sys/class/backlight/<backlight>/brightness.
+ *
+ * This value can be set in the backlight_properties passed
+ * to devm_backlight_device_register() to set a default brightness
+ * value.
+ */
int brightness;
- /* Maximal value for brightness (read-only) */
+
+ /**
+ * @max_brightness: The maximum brightness value.
+ *
+ * This value must be set in the backlight_properties passed to
+ * devm_backlight_device_register() and shall not be modified by the
+ * driver after registration.
+ */
int max_brightness;
- /* Current FB Power mode (0: full on, 1..3: power saving
- modes; 4: full off), see FB_BLANK_XXX */
+
+ /**
+ * @power: The current power mode.
+ *
+ * User space can configure the power mode using the sysfs
+ * attribute: /sys/class/backlight/<backlight>/bl_power
+ * When the power property is updated update_status() is called.
+ *
+ * The possible values are: (0: full on, 1 to 3: power saving
+ * modes; 4: full off), see FB_BLANK_XXX.
+ *
+ * When the backlight device is enabled @power is set
+ * to FB_BLANK_UNBLANK. When the backlight device is disabled
+ * @power is set to FB_BLANK_POWERDOWN.
+ */
int power;
- /* FB Blanking active? (values as for power) */
- /* Due to be removed, please use (state & BL_CORE_FBBLANK) */
+
+ /**
+ * @fb_blank: The power state from the FBIOBLANK ioctl.
+ *
+ * When the FBIOBLANK ioctl is called @fb_blank is set to the
+ * blank parameter and the update_status() operation is called.
+ *
+ * When the backlight device is enabled @fb_blank is set
+ * to FB_BLANK_UNBLANK. When the backlight device is disabled
+ * @fb_blank is set to FB_BLANK_POWERDOWN.
+ *
+ * Backlight drivers should avoid using this property. It has been
+ * replaced by state & BL_CORE_FBLANK (although most drivers should
+ * use backlight_is_blank() as the preferred means to get the blank
+ * state).
+ *
+ * fb_blank is deprecated and will be removed.
+ */
int fb_blank;
- /* Backlight type */
+
+ /**
+ * @type: The type of backlight supported.
+ *
+ * The backlight type allows userspace to make appropriate
+ * policy decisions based on the backlight type.
+ *
+ * This value must be set in the backlight_properties
+ * passed to devm_backlight_device_register().
+ */
enum backlight_type type;
- /* Flags used to signal drivers of state changes */
+
+ /**
+ * @state: The state of the backlight core.
+ *
+ * The state is a bitmask. BL_CORE_FBBLANK is set when the display
+ * is expected to be blank. BL_CORE_SUSPENDED is set when the
+ * driver is suspended.
+ *
+ * backlight drivers are expected to use backlight_is_blank()
+ * in their update_status() operation rather than reading the
+ * state property.
+ *
+ * The state is maintained by the core and drivers may not modify it.
+ */
unsigned int state;
- /* Type of the brightness scale (linear, non-linear, ...) */
- enum backlight_scale scale;
#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */
+ /**
+ * @scale: The type of the brightness scale.
+ */
+ enum backlight_scale scale;
};
+/**
+ * struct backlight_device - backlight device data
+ *
+ * This structure holds all data required by a backlight device.
+ */
struct backlight_device {
- /* Backlight properties */
+ /**
+ * @props: Backlight properties
+ */
struct backlight_properties props;
- /* Serialise access to update_status method */
+ /**
+ * @update_lock: The lock used when calling the update_status() operation.
+ *
+ * update_lock is an internal backlight lock that serialise access
+ * to the update_status() operation. The backlight core holds the update_lock
+ * when calling the update_status() operation. The update_lock shall not
+ * be used by backlight drivers.
+ */
struct mutex update_lock;
- /* This protects the 'ops' field. If 'ops' is NULL, the driver that
- registered this device has been unloaded, and if class_get_devdata()
- points to something in the body of that driver, it is also invalid. */
+ /**
+ * @ops_lock: The lock used around everything related to backlight_ops.
+ *
+ * ops_lock is an internal backlight lock that protects the ops pointer
+ * and is used around all accesses to ops and when the operations are
+ * invoked. The ops_lock shall not be used by backlight drivers.
+ */
struct mutex ops_lock;
+
+ /**
+ * @ops: Pointer to the backlight operations.
+ *
+ * If ops is NULL, the driver that registered this device has been unloaded,
+ * and if class_get_devdata() points to something in the body of that driver,
+ * it is also invalid.
+ */
const struct backlight_ops *ops;
- /* The framebuffer notifier block */
+ /**
+ * @fb_notif: The framebuffer notifier block
+ */
struct notifier_block fb_notif;
- /* list entry of all registered backlight devices */
+ /**
+ * @entry: List entry of all registered backlight devices
+ */
struct list_head entry;
+ /**
+ * @dev: Parent device.
+ */
struct device dev;
- /* Multiple framebuffers may share one backlight device */
+ /**
+ * @fb_bl_on: The state of individual fbdev's.
+ *
+ * Multiple fbdev's may share one backlight device. The fb_bl_on
+ * records the state of the individual fbdev.
+ */
bool fb_bl_on[FB_MAX];
+ /**
+ * @use_count: The number of uses of fb_bl_on.
+ */
int use_count;
};
+/**
+ * backlight_update_status - force an update of the backlight device status
+ * @bd: the backlight device
+ */
static inline int backlight_update_status(struct backlight_device *bd)
{
int ret = -ENOENT;
put_device(&bd->dev);
}
+/**
+ * backlight_is_blank - Return true if display is expected to be blank
+ * @bd: the backlight device
+ *
+ * Display is expected to be blank if any of these is true::
+ *
+ * 1) if power in not UNBLANK
+ * 2) if fb_blank is not UNBLANK
+ * 3) if state indicate BLANK or SUSPENDED
+ *
+ * Returns true if display is expected to be blank, false otherwise.
+ */
+static inline bool backlight_is_blank(const struct backlight_device *bd)
+{
+ return bd->props.power != FB_BLANK_UNBLANK ||
+ bd->props.fb_blank != FB_BLANK_UNBLANK ||
+ bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK);
+}
+
extern struct backlight_device *backlight_device_register(const char *name,
struct device *dev, void *devdata, const struct backlight_ops *ops,
const struct backlight_properties *props);
#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
+/**
+ * bl_get_data - access devdata
+ * @bl_dev: pointer to backlight device
+ *
+ * When a backlight device is registered the driver has the possibility
+ * to supply a void * devdata. bl_get_data() return a pointer to the
+ * devdata.
+ *
+ * RETURNS:
+ *
+ * pointer to devdata stored while registering the backlight device.
+ */
static inline void * bl_get_data(struct backlight_device *bl_dev)
{
return dev_get_drvdata(&bl_dev->dev);
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