From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jingoo Han Date: Tue, 26 Nov 2013 04:27:11 +0000 Subject: Re: [PATCH v2] video: backlight: Remove backlight sysfs uevent Message-Id: <001001ceea5f$c6642e50$532c8af0$%han@samsung.com> List-Id: References: <20131112033906.GA30454@july> In-Reply-To: <20131112033906.GA30454@july> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: 'Andrew Morton' Cc: 'Kyungmin Park' , 'Richard Purdie' , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, 'Kay Sievers' , 'Jingoo Han' On Tuesday, November 12, 2013 12:39 PM, Kyungmin Park wrote: > > From: Kyungmin Park > > 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 Acked-by: Jingoo Han Best regards, Jingoo Han > --- > 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);