From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: brightness control on thinkpad t61p Date: Tue, 8 Jan 2008 15:54:01 +0000 Message-ID: <20080108155401.GA4954@srcf.ucam.org> References: <20071226222321.GA32297@srcf.ucam.org> <20071227123358.GB25535@khazad-dum.debian.net> <20080107013623.GA6667@khazad-dum.debian.net> <20080107194833.GA22506@srcf.ucam.org> <20080108003246.GA15587@khazad-dum.debian.net> <20080108004559.GA27177@srcf.ucam.org> <20080108120653.GA23216@khazad-dum.debian.net> <20080108121819.GA1324@srcf.ucam.org> <20080108124820.GB23216@khazad-dum.debian.net> <1199807102.6053.31.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cavan.codon.org.uk ([78.32.9.130]:53079 "EHLO vavatch.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbYAHPyN (ORCPT ); Tue, 8 Jan 2008 10:54:13 -0500 Content-Disposition: inline In-Reply-To: <1199807102.6053.31.camel@localhost.localdomain> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Richard Purdie Cc: Henrique de Moraes Holschuh , Andrew Morton , linux-acpi@vger.kernel.org, "Rafael J. Wysocki" On Tue, Jan 08, 2008 at 03:45:02PM +0000, Richard Purdie wrote: > I did't get enough context above but I went through the archives and it > seems this is about linearising backlight values. Indeed. The ACPI spec provides a range of 0-100, without specifying what this actually means (it gives brightness and power consumption as two different examples). Implementations are only required to support a subset of these, with the others being ignored. The current hook into the backlight class exports this range but provides no means for an application to determine which values are valid - I'd prefer to just flatten the range to remove the holes. Given the lack of standardisation in the real meaning of the values, I don't think exporting the 0-100 range buys us anything. -- Matthew Garrett | mjg59@srcf.ucam.org