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 register its own on Win8 systems).
Signed-off-by: Aaron Lu aaron.lu@intel.com --- drivers/video/backlight/backlight.c | 31 +++++++++++++++++++++++++++++++ include/linux/backlight.h | 4 ++++ 2 files changed, 35 insertions(+)
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 94a403a..5d05555 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -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; }
diff --git a/include/linux/backlight.h b/include/linux/backlight.h index 53b7794..5f9cd96 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -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)