From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422706AbXBOXZA (ORCPT ); Thu, 15 Feb 2007 18:25:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422704AbXBOXZA (ORCPT ); Thu, 15 Feb 2007 18:25:00 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:42154 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1422706AbXBOXY7 (ORCPT ); Thu, 15 Feb 2007 18:24:59 -0500 Date: Fri, 16 Feb 2007 00:24:38 +0100 From: Pavel Machek To: Richard Purdie Cc: =?iso-8859-1?Q?N=E9meth_M=E1rton?= , Dmitry Torokhov , linux-input@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org Subject: Re: [PATCH] input: extend EV_LED Message-ID: <20070215232438.GB4176@elf.ucw.cz> References: <1171580944.5839.38.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1171580944.5839.38.camel@localhost.localdomain> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > > >I do not know the LED subsystem in detail, but I do not > > > > >know any possibility to access the i8042 from different > > > > >subsystem than the input subsystem. > > > > > > > > > >What do you think and recommend? > > > > > > > > I think you need to use leds framework for what you are > > > > trying to do. > > > > > > I'm actually not sure if led framework can do that. It was > > > designed for leds on gpios, and handles blinking itself. > > The led framework is generic. If you can write a function to turn it > on/off you can drive it with the LED framework. Even if that function is slow and sleeps? > > > But he could export two leds :-). > > > > what do you mean about two leds? The first one would be > > off/0.5Hz and the other off/1Hz? > > > > I read in linux/Documentation/led-class.txt the following: > > > > | Some leds can be programmed to flash in hardware. As this > > isn't a generic > > | LED device property, this should be exported as a device > > specific sysfs > > | attribute rather than part of the class if this > > functionality is required. > > > > Does it mean that neither the input subsystem nor the led > > subsystem is designed for hardware acelerated blinking leds? > > Is there any usual way what attribute a hw accelerated > > blinking LED_MAIL should export? > > This has been discussed in several places several times. The problem > with hardware accelerated flashing is that you're are often limited to > certain constraints (this case being no exception) and indicating what > these are to userspace in a generic fashion is difficult. > > One way I've come up with is adds capability to the class to have LED > specific triggers and you can then expose these hardware capabilities as > an extra trigger specific to the LED. > > Another proposal more specific to this use case was to have some > information behind the scenes which the software timer based trigger > could use to turn on the "hardware acceleration" if present and capable > of the requested mode. This might just need a function pointer in the > core so could be quite neat. I do not think we want to permit this led to run in "not accelerated" mode. I believe i8042 accesses are pretty expensive. > Nether patch exists yet. Yep, interested party should create one of them :-). (And I'd prefer the first one, due to i8042 slowness). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html