From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755873AbZKJD0a (ORCPT ); Mon, 9 Nov 2009 22:26:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755282AbZKJD0a (ORCPT ); Mon, 9 Nov 2009 22:26:30 -0500 Received: from mail-yw0-f202.google.com ([209.85.211.202]:53325 "EHLO mail-yw0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754224AbZKJD03 (ORCPT ); Mon, 9 Nov 2009 22:26:29 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=EfoFTxo41A0jsfz8Cbq7t+GIDg5GOMdNwLrWmmBbB8N4uZiuLHAEuvkzsMBu/tIZN6 YYLkIWJuVdnXaSDwaLBlp2PVVBFXJQgPP/FZpG6KfQcUjxuAIXrmWWI+TP9YhTuCZLU3 /szSEPZj4gV6NnY5V/VnYcSym9kKg2vchyTng= MIME-Version: 1.0 In-Reply-To: <1257809705.29038.82.camel@dax.rpnet.com> References: <90b950fc0911020050q3bc3fae8j954ec6ed73d79b5@mail.gmail.com> <1257809705.29038.82.camel@dax.rpnet.com> Date: Tue, 10 Nov 2009 12:26:32 +0900 Message-ID: <90b950fc0911091926v32dc1c44n1018322390282bc0@mail.gmail.com> Subject: Re: [patch] added brightness feature to lcd class. From: InKi Dae To: Richard Purdie Cc: linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Kyungmin Park , Andrew Morton , Pavel Machek Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thank you for your comments. it is a good idea that lcd driver registers interfaces to lcd class and backlight class. but I think for AMOLED LCD Panel, backlight couldn't be real device so power on/off for backlight device doesn't make sense. I had tried lcd driver registers interfaces to lcd class and backlight class as you said. and also backlight fake driver as Pavel said. but I thought to use my patch is more simple and effective. of course, this patch has a problem that it has different path from backlight class for controlling brightness. how about creating symbolic link file for competiability? Best Regards, InKi Dae. 2009/11/10 Richard Purdie : > On Mon, 2009-11-02 at 17:50 +0900, InKi Dae wrote: >> This patch adds brightness feature to lcd class. >> (kernel/driver/video/backlight/lcd.c) >> >> In the past, most of the lcd panels for embedded system was TFT-LCD >> Panel needing backlight device. >> But now AMOLED LCD Panel appeared so we should consider brightness >> control for AMOLED Panel. >> >> For the time being, I used backlight fake driver for brightness >> control of AMOLED LCD Panel. >> But this way is not good, so I propose to add brightness feature to lcd class. >> >> For this, I attached patch file and if my proposal is approved >> Then I will send s6e63m0 and tl2796 AMOLED lcd panel driver based on >> lcd class modified soon. > > Pavel has a good point but let me try and explain it differently. > > The point of the backlight class is to expose a backlight brightness > control to userspace in a consistent well defined way. Anyone wishing to > write a piece of software to control the brightness of a backlight then > only needs to support *one* interface. > > It is entirely accepted and normal that multiple "class" devices may > appear in userspace for one piece of physical hardware. > > Your patch duplicates a userspace API and means any backlight > application would have to look for *two* different interfaces. This is > unacceptable. > > Why can't your driver just register a backlight interface and an LCD > interface? I'd imagine your backlight and LCD can be powered on/off > separately too. > > Please also cc: the backlight/lcd maintainer (me) on backlight/lcd > patches in future. > > Andrew: Can you drop that patch from -mm please as I'm not convinced we > need two backlight brightness interfaces around... > > Cheers, > > Richard > > > >