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backlight: backlight: Add overview and update existing doc
Add overview chapter to backlight.c. Update existing kernel-doc to follow a more consistent style and drop kernel-doc for deprecated functions. Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> Signed-off-by: Lee Jones <lee.jones@linaro.org>
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Sam Ravnborg
Lee Jones
parent
9c4aa3118b
commit
a1230eb2e3
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@ -22,6 +22,47 @@
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#include <asm/backlight.h>
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#endif
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/**
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* DOC: overview
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*
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* The backlight core supports implementing backlight drivers.
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*
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* A backlight driver registers a driver using
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* devm_backlight_device_register(). The properties of the backlight
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* driver such as type and max_brightness must be specified.
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* When the core detect changes in for example brightness or power state
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* the update_status() operation is called. The backlight driver shall
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* implement this operation and use it to adjust backlight.
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*
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* Several sysfs attributes are provided by the backlight core::
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*
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* - brightness R/W, set the requested brightness level
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* - actual_brightness RO, the brightness level used by the HW
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* - max_brightness RO, the maximum brightness level supported
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*
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* See Documentation/ABI/stable/sysfs-class-backlight for the full list.
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*
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* The backlight can be adjusted using the sysfs interface, and
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* the backlight driver may also support adjusting backlight using
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* a hot-key or some other platform or firmware specific way.
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*
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* The driver must implement the get_brightness() operation if
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* the HW do not support all the levels that can be specified in
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* brightness, thus providing user-space access to the actual level
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* via the actual_brightness attribute.
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*
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* When the backlight changes this is reported to user-space using
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* an uevent connected to the actual_brightness attribute.
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* When brightness is set by platform specific means, for example
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* a hot-key to adjust backlight, the driver must notify the backlight
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* core that brightness has changed using backlight_force_update().
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*
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* The backlight driver core receives notifications from fbdev and
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* if the event is FB_EVENT_BLANK and if the value of blank, from the
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* FBIOBLANK ioctrl, results in a change in the backlight state the
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* update_status() operation is called.
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*/
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static struct list_head backlight_dev_list;
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static struct mutex backlight_dev_list_mutex;
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static struct blocking_notifier_head backlight_notifier;
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@ -40,9 +81,17 @@ static const char *const backlight_scale_types[] = {
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#if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
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defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
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/* This callback gets called when something important happens inside a
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* framebuffer driver. We're looking if that important event is blanking,
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* and if it is and necessary, we're switching backlight power as well ...
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/*
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* fb_notifier_callback
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*
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* This callback gets called when something important happens inside a
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* framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK
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* which is reported to the driver using backlight_update_status()
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* as a state change.
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*
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* There may be several fbdev's connected to the backlight device,
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* in which case they are kept track of. A state change is only reported
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* if there is a change in backlight for the specified fbdev.
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*/
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static int fb_notifier_callback(struct notifier_block *self,
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unsigned long event, void *data)
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@ -324,7 +373,10 @@ ATTRIBUTE_GROUPS(bl_device);
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* @reason: reason for update
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*
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* Updates the internal state of the backlight in response to a hardware event,
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* and generate a uevent to notify userspace
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* and generates an uevent to notify userspace. A backlight driver shall call
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* backlight_force_update() when the backlight is changed using, for example,
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* a hot-key. The updated brightness is read using get_brightness() and the
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* brightness value is reported using an uevent.
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*/
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void backlight_force_update(struct backlight_device *bd,
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enum backlight_update_reason reason)
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@ -337,20 +389,7 @@ void backlight_force_update(struct backlight_device *bd,
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}
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EXPORT_SYMBOL(backlight_force_update);
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/**
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* backlight_device_register - create and register a new object of
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* backlight_device class.
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* @name: the name of the new object(must be the same as the name of the
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* respective framebuffer device).
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* @parent: a pointer to the parent device
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* @devdata: an optional pointer to be stored for private driver use. The
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* methods may retrieve it by using bl_get_data(bd).
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* @ops: the backlight operations structure.
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* @props: pointer to backlight's properties structure.
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*
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* Creates and registers new backlight device. Returns either an
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* ERR_PTR() or a pointer to the newly allocated device.
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*/
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/* deprecated - use devm_backlight_device_register() */
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struct backlight_device *backlight_device_register(const char *name,
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struct device *parent, void *devdata, const struct backlight_ops *ops,
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const struct backlight_properties *props)
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@ -417,6 +456,15 @@ struct backlight_device *backlight_device_register(const char *name,
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}
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EXPORT_SYMBOL(backlight_device_register);
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/** backlight_device_get_by_type - find first backlight device of a type
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* @type: the type of backlight device
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*
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* Look up the first backlight device of the specified type
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*
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* RETURNS:
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*
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* Pointer to backlight device if any was found. Otherwise NULL.
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*/
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struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
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{
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bool found = false;
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@ -456,12 +504,7 @@ struct backlight_device *backlight_device_get_by_name(const char *name)
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}
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EXPORT_SYMBOL(backlight_device_get_by_name);
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/**
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* backlight_device_unregister - unregisters a backlight device object.
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* @bd: the backlight device object to be unregistered and freed.
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*
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* Unregisters a previously registered via backlight_device_register object.
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*/
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/* deprecated - use devm_backlight_device_unregister() */
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void backlight_device_unregister(struct backlight_device *bd)
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{
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if (!bd)
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@ -509,10 +552,12 @@ static int devm_backlight_device_match(struct device *dev, void *res,
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* backlight_register_notifier - get notified of backlight (un)registration
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* @nb: notifier block with the notifier to call on backlight (un)registration
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*
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* @return 0 on success, otherwise a negative error code
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*
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* Register a notifier to get notified when backlight devices get registered
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* or unregistered.
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*
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* RETURNS:
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*
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* 0 on success, otherwise a negative error code
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*/
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int backlight_register_notifier(struct notifier_block *nb)
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{
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@ -524,10 +569,12 @@ EXPORT_SYMBOL(backlight_register_notifier);
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* backlight_unregister_notifier - unregister a backlight notifier
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* @nb: notifier block to unregister
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*
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* @return 0 on success, otherwise a negative error code
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*
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* Register a notifier to get notified when backlight devices get registered
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* or unregistered.
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*
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* RETURNS:
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*
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* 0 on success, otherwise a negative error code
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*/
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int backlight_unregister_notifier(struct notifier_block *nb)
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{
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@ -536,19 +583,21 @@ int backlight_unregister_notifier(struct notifier_block *nb)
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EXPORT_SYMBOL(backlight_unregister_notifier);
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/**
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* devm_backlight_device_register - resource managed backlight_device_register()
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* devm_backlight_device_register - register a new backlight device
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* @dev: the device to register
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* @name: the name of the device
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* @parent: a pointer to the parent device
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* @parent: a pointer to the parent device (often the same as @dev)
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* @devdata: an optional pointer to be stored for private driver use
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* @ops: the backlight operations structure
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* @props: the backlight properties
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*
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* @return a struct backlight on success, or an ERR_PTR on error
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* Creates and registers new backlight device. When a backlight device
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* is registered the configuration must be specified in the @props
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* parameter. See description of &backlight_properties.
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*
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* Managed backlight_device_register(). The backlight_device returned
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* from this function are automatically freed on driver detach.
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* See backlight_device_register() for more information.
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* RETURNS:
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*
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* struct backlight on success, or an ERR_PTR on error
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*/
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struct backlight_device *devm_backlight_device_register(struct device *dev,
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const char *name, struct device *parent, void *devdata,
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@ -576,13 +625,13 @@ struct backlight_device *devm_backlight_device_register(struct device *dev,
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EXPORT_SYMBOL(devm_backlight_device_register);
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/**
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* devm_backlight_device_unregister - resource managed backlight_device_unregister()
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* devm_backlight_device_unregister - unregister backlight device
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* @dev: the device to unregister
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* @bd: the backlight device to unregister
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*
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* Deallocated a backlight allocated with devm_backlight_device_register().
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* Deallocates a backlight allocated with devm_backlight_device_register().
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* Normally this function will not need to be called and the resource management
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* code will ensure that the resource is freed.
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* code will ensure that the resources are freed.
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*/
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void devm_backlight_device_unregister(struct device *dev,
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struct backlight_device *bd)
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@ -673,12 +722,19 @@ static void devm_backlight_release(void *data)
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}
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/**
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* devm_of_find_backlight - Resource-managed of_find_backlight()
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* @dev: Device
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* devm_of_find_backlight - find backlight for a device
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* @dev: the device
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*
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* Device managed version of of_find_backlight().
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* The reference on the backlight device is automatically
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* This function looks for a property named 'backlight' on the DT node
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* connected to @dev and looks up the backlight device. The lookup is
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* device managed so the reference to the backlight device is automatically
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* dropped on driver detach.
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*
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* RETURNS:
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*
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* A pointer to the backlight device if found.
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* Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
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* device is found. NULL if there's no backlight property.
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*/
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struct backlight_device *devm_of_find_backlight(struct device *dev)
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{
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