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...@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)
--
1.8.4.12.g2ea3df6
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