From: Kyungmin Park <kyungmin.p...@samsung.com>
The most mobile phones have Ambient Light Sensors and it changes brightness
according lux.
It means it changes backlight brightness frequently by just writing sysfs node,
so it generates uevent.
Usually there's no user to use this backlight changes. But it forks udev worker
threads and it takes about 5ms. The main problem is that it hurts other process
activities. so remove it.
Kay said
"Uevents are for the major, low-frequent, global device state-changes,
not for carrying-out any sort of measurement data. Subsystems which
need that should use other facilities like poll()-able sysfs file or
any other subscription-based, client-tracking interface which does not
cause overhead if it isn't used. Uevents are not the right thing to
use here, and upstream udev should not paper-over broken kernel
subsystems."
Signed-off-by: Kyungmin Park <kyungmin.p...@samsung.com>
---
v1: there's still user to use BACKLIGHT_UPDATE_SYSFS. so just remove store
sysfs node uevent
---
diff --git a/drivers/video/backlight/backlight.c
b/drivers/video/backlight/backlight.c
index 94a403a..292cf99 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -172,8 +172,6 @@ static ssize_t brightness_store(struct device *dev,
}
mutex_unlock(&bd->ops_lock);
- backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
-
return rc;
}
static DEVICE_ATTR_RW(brightness);
--
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