From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Purdie Subject: Re: brightness control on thinkpad t61p Date: Tue, 08 Jan 2008 16:29:31 +0000 Message-ID: <1199809771.6053.42.camel@localhost.localdomain> 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> <20080108155401.GA4954@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from tim.rpsys.net ([194.106.48.114]:48144 "EHLO tim.rpsys.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756243AbYAHQ3z (ORCPT ); Tue, 8 Jan 2008 11:29:55 -0500 In-Reply-To: <20080108155401.GA4954@srcf.ucam.org> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Matthew Garrett Cc: Henrique de Moraes Holschuh , Andrew Morton , linux-acpi@vger.kernel.org, "Rafael J. Wysocki" On Tue, 2008-01-08 at 15:54 +0000, Matthew Garrett wrote: > 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. I agree with that. 0-100 actually breaks a useful and valid way the class gets used in the "brightness + 1" case... Cheers, Richard