Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754620AbXJ1RWM (ORCPT ); Sun, 28 Oct 2007 13:22:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750978AbXJ1RV6 (ORCPT ); Sun, 28 Oct 2007 13:21:58 -0400 Received: from mailgw2.3essentials.com ([66.179.153.59]:1907 "EHLO mailgw2.3essentials.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750841AbXJ1RV5 (ORCPT ); Sun, 28 Oct 2007 13:21:57 -0400 X-Greylist: delayed 899 seconds by postgrey-1.27 at vger.kernel.org; Sun, 28 Oct 2007 13:21:57 EDT Message-ID: <4724CF9F.6050908@antonello.org> Date: Sun, 28 Oct 2007 19:06:23 +0100 From: "lists@antonello.org" User-Agent: Thunderbird 2.0.0.6 (X11/20070728) MIME-Version: 1.0 To: Matt Domsch CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] Dell laptop backlight driver References: <4724B4F5.80004@antonello.org> <20071028161955.GF23359@auslistsprd01.us.dell.com> In-Reply-To: <20071028161955.GF23359@auslistsprd01.us.dell.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2227 Lines: 49 Matt Domsch wrote: > On Sun, Oct 28, 2007 at 05:12:37PM +0100, jack@antonello.org wrote: >> Hello, >> this driver implements backlight control on Dell laptops >> which use SMI for changing brightness levels. >> >> The driver is INCOMPLETE since it is unable to probe some required >> parameters >> in order to perform backlight control. Such parameters are found in a Dell >> proprietary DMI table which should be parsed. For now external tools may be >> used to find these parameters by hand. So if you intend to try this out, >> FIRST write your laptop model parameters correctly inside the source code >> as explained in Documentation/dell-laptop.txt. >> >> Parts of this driver may also be used to provide additional functionalities >> similarly to the drivers/misc/*-laptop.c drivers. > > Why is this better done in the kernel rather than in userspace with > libsmbios as you've noted? > I had to do a kernelspace driver for controlling the backlight. This was part of a college project assignment. In order for it to be valid for an operating system course, it had to be in kernelspace (not Unix programming) :). As i mentioned that can be done in userspace and it IS sensible to do so. I know that the code which was already written for Dell implied a userspace approach, but i simply had no choice. I also don't expect this driver to become mainstream, but since i have written it, other people might want to have a look at it. Finally i really don't think there's any sensible way of implementing Linux LCD Backlight Abstraction relying on a userspace application. That would mean the kernel calling userspace code to change the brightness, then this latter code would again call the kernel to trigger a SMI and so on. That's just not a good design. I think a userspace solution implies choosing NOT to implement the LCD Abstraction. Causing Dell laptops to be treated differently from other machines (as they are not compliant with Linux's own interface). jacopo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/