From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Purdie Subject: Re: [PATCH 1/2] video: always update the brightness when poking "brightness" Date: Tue, 30 Dec 2008 10:34:10 +0000 Message-ID: <1230633250.5328.8.camel@dax.rpnet.com> References: <1230088058.562.219.camel@rzhang-dt> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from 93-97-173-237.zone5.bethere.co.uk ([93.97.173.237]:64108 "EHLO tim.rpsys.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751929AbYL3LGJ (ORCPT ); Tue, 30 Dec 2008 06:06:09 -0500 In-Reply-To: <1230088058.562.219.camel@rzhang-dt> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Zhang Rui Cc: linux-acpi , Len Brown On Wed, 2008-12-24 at 11:07 +0800, Zhang Rui wrote: > bd->props.brightness is a cached value. > the current code has some potential problems when poking the > backlight I/F. > > For example, > 1. set the brightness level to 5 via sysfs I/F > 2. set the backlight to another level via the procfs, > 3. setting it back to 5 doesn't work because bd->props.brightness > is still 5. > > http://bugzilla.kernel.org/show_bug.cgi?id=12249 The root of the problem here is that there are two interfaces controlling the same piece of hardware. Personally, I'd like to see the proc interfaces to backlights depreacated but we do need to make them work I guess. The real bug looks like the proc interface should update props.brightness for that hardware... Cheers, Richard -- Richard Purdie Intel Open Source Technology Centre