From d98895ac89b602e37d640c53a04c68333f0bd97d Mon Sep 17 00:00:00 2001 From: Kyungmin Park Date: Thu, 22 May 2014 10:43:37 +1000 Subject: [PATCH] drivers/video/backlight/backlight.c: remove backlight sysfs uevent Most mobile phones have Ambient Light Sensors and it changes brightness according to the 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 Cc: Henrique de Moraes Holschuh Cc: Matthew Garrett Cc: Kay Sievers Acked-by: Jingoo Han Cc: Henrique de Moraes Holschuh Cc: Richard Purdie Signed-off-by: Andrew Morton --- drivers/video/backlight/backlight.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index bd2172c2d650..31672740fe28 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -189,8 +189,6 @@ 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); -- 2.39.5