From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Renninger Subject: Re: [RFC PATCH 1/5] ACPI video: check the return value of acpi_video_device_lcd_get_level_current Date: Wed, 11 Mar 2009 14:15:27 +0100 Message-ID: <200903111415.28681.trenn@suse.de> References: <1236672205.2820.119.camel@rzhang-dt> <200903111356.01710.trenn@suse.de> <20090311130432.GA21313@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ns.suse.de ([195.135.220.2]:52736 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752195AbZCKNPc (ORCPT ); Wed, 11 Mar 2009 09:15:32 -0400 In-Reply-To: <20090311130432.GA21313@srcf.ucam.org> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Matthew Garrett Cc: Zhang Rui , linux-acpi , Len Brown On Wednesday 11 March 2009 14:04:32 Matthew Garrett wrote: > On Wed, Mar 11, 2009 at 01:56:00PM +0100, Thomas Renninger wrote: > > > (BTW, I recently saw a BIOS with _BCQ function. They said they are going to > > fix it, but it may be more widespread, e.g. this also is often the case > > (missing _BQC) on Samsung). I found it by luck disassembling and > > recompiling the DSDT, a runtime warning would be nice (if it does not > > already exist). > > It's not that uncommon - there's a few machines with _BCQ. I actually > thought we handled it already, but it seems not. Just adding a cap._BCQ > and using it if there's no _BQC sounds like a safe idea. As said, the current brightness must be initialized if there is no _BQC and Rui seem to have been removed that. Also a: printk (KERN_WARN FW_BUG PREFIX "ACPI brightness control misses _BQC function\n"); should be added. Rui, if you are there already, do you mind to add such test. I found by pure luck that a vendor mixed up _BQC and _BCQ by getting one single warning recompiling the DSDT: "_BCQ not a predefined function" (or similar). They are now adding it, but a warning is appropriate IMO in _BQC missing case. Not adding _BQC and doing brightness switching through ACPI brightness functions is a really bad idea in general. Thomas