/sys/class/backlight/.../brightness returns a cached value,
which confuses a lot of users.
Make the "brightness" reflect the actual backlight levels,
and mark /sys/class/backlight/.../brightness as depreacated
in this patch.
Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
---
drivers/video/backlight/Kconfig | 17 +++++++++++++++++
drivers/video/backlight/backlight.c | 11 ++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)
Index: linux-2.6/drivers/video/backlight/Kconfig
===================================================================
--- linux-2.6.orig/drivers/video/backlight/Kconfig
+++ linux-2.6/drivers/video/backlight/Kconfig
@@ -98,6 +98,23 @@ config BACKLIGHT_CLASS_DEVICE
To have support for your specific LCD panel you will have to
select the proper drivers which depend on this option.
+config BACKLIGHT_CLASS_DEVICE_LEGACY_INTERFACE
+ bool "Deprecated lowlevel Backlight control legacy sysfs I/F"
+ depends on BACKLIGHT_CLASS_DEVICE
+ default y
+ help
+ "brightness" file used to return a cached brightness level.
+ And users need to poke the "actual_brightness" to get the
+ correct current backlight level.
+ Now the "brightness" file always reflects the actual
+ brightness and "actual_brightness" is superfluous.
+
+ Some applications including X still use this file to get the current
+ backlight level, thus we can not remove it immediately.
+
+ Say N here if you're sure no application depends on the
+ "actual_brightness" file.
+
config BACKLIGHT_ATMEL_LCDC
bool "Atmel LCDC Contrast-as-Backlight control"
depends on BACKLIGHT_CLASS_DEVICE && FB_ATMEL
Index: linux-2.6/drivers/video/backlight/backlight.c
===================================================================
--- linux-2.6.orig/drivers/video/backlight/backlight.c
+++ linux-2.6/drivers/video/backlight/backlight.c
@@ -108,9 +108,14 @@ static ssize_t backlight_store_power(str
static ssize_t backlight_show_brightness(struct device *dev,
struct device_attribute *attr, char *buf)
{
+ int rc = -ENXIO;
struct backlight_device *bd = to_backlight_device(dev);
- return sprintf(buf, "%d\n", bd->props.brightness);
+ mutex_lock(&bd->ops_lock);
+ if (bd->ops && bd->ops->get_brightness)
+ rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
+ mutex_unlock(&bd->ops_lock);
+ return rc;
}
static ssize_t backlight_store_brightness(struct device *dev,
@@ -152,6 +157,7 @@ static ssize_t backlight_show_max_bright
return sprintf(buf, "%d\n", bd->props.max_brightness);
}
+#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE_LEGACY_INTERFACE
static ssize_t backlight_show_actual_brightness(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -165,6 +171,7 @@ static ssize_t backlight_show_actual_bri
return rc;
}
+#endif
static struct class *backlight_class;
@@ -178,8 +185,10 @@ static struct device_attribute bl_device
__ATTR(bl_power, 0644, backlight_show_power, backlight_store_power),
__ATTR(brightness, 0644, backlight_show_brightness,
backlight_store_brightness),
+#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE_LEGACY_INTERFACE
__ATTR(actual_brightness, 0444, backlight_show_actual_brightness,
NULL),
+#endif
__ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL),
__ATTR_NULL,
};
--
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