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backlight: Add backlight device (un)registration notification 

Some firmware drivers, ie acpi-video want to get themselves out of the
way (in some cases) when their also is a raw backlight device available.

Due to module loading ordering being unknown, acpi-video cannot be certain
that the backlight_device_registered(BACKLIGHT_RAW) it does for this is
the final verdict wrt there being a BACKLIGHT_RAW device.

By adding notification acpi-video can listen for backlight devices showing
up after it has loaded, and unregister its backlight device if desired.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Hans de Goede 2014-05-21 15:39:54 +02:00 committed by Rafael J. Wysocki
parent bee564430f
commit 3cc6919bd6
2 changed files with 47 additions and 0 deletions
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40
drivers/video/backlight/backlight.c
View File

@ -23,6 +23,7 @@
static struct list_head backlight_dev_list;
static struct mutex backlight_dev_list_mutex;
static struct blocking_notifier_head backlight_notifier;
static const char *const backlight_types[] = {
[BACKLIGHT_RAW] = "raw",
@ -370,6 +371,9 @@ struct backlight_device *backlight_device_register(const char *name,
list_add(&new_bd->entry, &backlight_dev_list);
mutex_unlock(&backlight_dev_list_mutex);
blocking_notifier_call_chain(&backlight_notifier,
BACKLIGHT_REGISTERED, new_bd);
return new_bd;
}
EXPORT_SYMBOL(backlight_device_register);
@ -413,6 +417,10 @@ void backlight_device_unregister(struct backlight_device *bd)
pmac_backlight = NULL;
mutex_unlock(&pmac_backlight_mutex);
#endif
blocking_notifier_call_chain(&backlight_notifier,
BACKLIGHT_UNREGISTERED, bd);
mutex_lock(&bd->ops_lock);
bd->ops = NULL;
mutex_unlock(&bd->ops_lock);
@ -437,6 +445,36 @@ static int devm_backlight_device_match(struct device *dev, void *res,
return *r == data;
}
/**
* backlight_register_notifier - get notified of backlight (un)registration
* @nb: notifier block with the notifier to call on backlight (un)registration
*
* @return 0 on success, otherwise a negative error code
*
* Register a notifier to get notified when backlight devices get registered
* or unregistered.
*/
int backlight_register_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&backlight_notifier, nb);
}
EXPORT_SYMBOL(backlight_register_notifier);
/**
* backlight_unregister_notifier - unregister a backlight notifier
* @nb: notifier block to unregister
*
* @return 0 on success, otherwise a negative error code
*
* Register a notifier to get notified when backlight devices get registered
* or unregistered.
*/
int backlight_unregister_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&backlight_notifier, nb);
}
EXPORT_SYMBOL(backlight_unregister_notifier);
/**
* devm_backlight_device_register - resource managed backlight_device_register()
* @dev: the device to register
@ -544,6 +582,8 @@ static int __init backlight_class_init(void)
backlight_class->pm = &backlight_class_dev_pm_ops;
INIT_LIST_HEAD(&backlight_dev_list);
mutex_init(&backlight_dev_list_mutex);
BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
return 0;
}

7
include/linux/backlight.h
View File

@ -40,6 +40,11 @@ enum backlight_type {
BACKLIGHT_TYPE_MAX,
};
enum backlight_notification {
BACKLIGHT_REGISTERED,
BACKLIGHT_UNREGISTERED,
};
struct backlight_device;
struct fb_info;
@ -133,6 +138,8 @@ extern void devm_backlight_device_unregister(struct device *dev,
extern void backlight_force_update(struct backlight_device *bd,
enum backlight_update_reason reason);
extern bool backlight_device_registered(enum backlight_type type);
extern int backlight_register_notifier(struct notifier_block *nb);
extern int backlight_unregister_notifier(struct notifier_block *nb);
#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)