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backlight: introduce backlight_device_registered 

Introduce a new API for modules to query if a specific type of backlight
device has been registered. This is useful for some backlight device
provider module (e.g. ACPI video) to know if a native control
interface(e.g. the interface created by i915) is available and then do
things accordingly (e.g. avoid registering its own on Win8 systems).

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Aaron Lu 2013-10-11 21:27:43 +08:00 committed by Rafael J. Wysocki
parent 068aab7766
commit 5915a3db0c
2 changed files with 35 additions and 0 deletions
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31
drivers/video/backlight/backlight.c
View File

@ -21,6 +21,9 @@
#include <asm/backlight.h>
#endif
static struct list_head backlight_dev_list;
static struct mutex backlight_dev_list_mutex;
static const char *const backlight_types[] = {
[BACKLIGHT_RAW] = "raw",
[BACKLIGHT_PLATFORM] = "platform",
@ -349,10 +352,32 @@ struct backlight_device *backlight_device_register(const char *name,
mutex_unlock(&pmac_backlight_mutex);
#endif
mutex_lock(&backlight_dev_list_mutex);
list_add(&new_bd->entry, &backlight_dev_list);
mutex_unlock(&backlight_dev_list_mutex);
return new_bd;
}
EXPORT_SYMBOL(backlight_device_register);
bool backlight_device_registered(enum backlight_type type)
{
bool found = false;
struct backlight_device *bd;
mutex_lock(&backlight_dev_list_mutex);
list_for_each_entry(bd, &backlight_dev_list, entry) {
if (bd->props.type == type) {
found = true;
break;
}
}
mutex_unlock(&backlight_dev_list_mutex);
return found;
}
EXPORT_SYMBOL(backlight_device_registered);
/**
* backlight_device_unregister - unregisters a backlight device object.
* @bd: the backlight device object to be unregistered and freed.
@ -364,6 +389,10 @@ void backlight_device_unregister(struct backlight_device *bd)
if (!bd)
return;
mutex_lock(&backlight_dev_list_mutex);
list_del(&bd->entry);
mutex_unlock(&backlight_dev_list_mutex);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
if (pmac_backlight == bd)
@ -499,6 +528,8 @@ static int __init backlight_class_init(void)
backlight_class->dev_groups = bl_device_groups;
backlight_class->pm = &backlight_class_dev_pm_ops;
INIT_LIST_HEAD(&backlight_dev_list);
mutex_init(&backlight_dev_list_mutex);
return 0;
}

4
include/linux/backlight.h
View File

@ -100,6 +100,9 @@ struct backlight_device {
/* The framebuffer notifier block */
struct notifier_block fb_notif;
/* list entry of all registered backlight devices */
struct list_head entry;
struct device dev;
};
@ -123,6 +126,7 @@ extern void devm_backlight_device_unregister(struct device *dev,
struct backlight_device *bd);
extern void backlight_force_update(struct backlight_device *bd,
enum backlight_update_reason reason);
extern bool backlight_device_registered(enum backlight_type type);
#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)