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>
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 @@
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 @@
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 @@
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;
}