linux-kernel - Re: [PATCH] video: backlight: Remove backlight sysfs uevent

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Message-ID: <20131121143326.GA19773@srcf.ucam.org>
Date:	Thu, 21 Nov 2013 14:33:26 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Jingoo Han <jg1.han@...sung.com>,
	'Kyungmin Park' <kmpark@...radead.org>,
	'Henrique de Moraes Holschuh' <ibm-acpi@....eng.br>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kay@...y.org, 'Richard Purdie' <rpurdie@...ys.net>,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH] video: backlight: Remove backlight sysfs uevent

On Thu, Nov 21, 2013 at 09:43:32AM -0200, Henrique de Moraes Holschuh wrote:

> With this patchset applied, as far as I can tell anything that used to be
> uevent-driven by the backlight class will break: when a process changes the
> backlight using sysfs, other processes will not be notified of the change
> anymore.  This patchset seems to break backlight uevent support in such a
> way that basically renders the entire thing useless and you might as well
> just remove uevent support entirely.

The uevent support was initially added to handle systems where pressing 
a hotkey generates an event (good) but the firmware automatically 
changes the brightness (bad). I have absolutely no idea why I added 
BACKLIGHT_UPDATE_SYSFS - BACKLIGHT_UPDATE_HOTKEY solves the problem I 
was trying to solve. I'm not aware of any userspace that relies on 
BACKLIGHT_UPDATE_SYSFS.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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