Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030377AbVKCQgN (ORCPT ); Thu, 3 Nov 2005 11:36:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030382AbVKCQgM (ORCPT ); Thu, 3 Nov 2005 11:36:12 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:52411 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S1030377AbVKCQgL (ORCPT ); Thu, 3 Nov 2005 11:36:11 -0500 Date: Thu, 3 Nov 2005 17:35:32 +0100 From: Pavel Machek To: John Lenz , Robert Schwebel , Robert Schwebel , vojtech@suse.cz, rpurdie@rpsys.net, kernel list Subject: Re: best way to handle LEDs Message-ID: <20051103163532.GC24846@elf.ucw.cz> References: <20051101234459.GA443@elf.ucw.cz> <20051102202622.GN23316@pengutronix.de> <20051102211334.GH23943@elf.ucw.cz> <20051102213354.GO23316@pengutronix.de> <38523.192.168.0.12.1130986361.squirrel@192.168.0.2> <20051103081522.GA21663@flint.arm.linux.org.uk> <20051103095725.GA703@openzaurus.ucw.cz> <20051103144904.GG28038@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051103144904.GG28038@flint.arm.linux.org.uk> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1244 Lines: 33 Hi! > > > > Except the led code that is being proposed CAN sit on top of a generic > > > > GPIO layer. > > > > > > I also have issues with a generic GPIO layer. As I mentioned in the > > > past, there's serious locking issues with any generic abstraction of > > > GPIOs. > > > > > > 1. You want to be able to change GPIO state from interrupts. This > > > implies you can not sleep in GPIO state changing functions. > > > > > > 2. Some GPIOs are implemented on I2C devices. This means that to > > > change state, you must sleep. > > > > Can't you just busywait? Yes, it is ugly in general, but perhaps it > > is better than alternatives... > > Does the i2c layer support busy waiting or are you suggesting something > else? I'm suggesting that adding busy wait support to i2c is probably good idea. GPIOs are on many small machines, and there are machine (spitz/akita?) that differ mainly in "where GPIO lines are connected". That cries for GPIO layer. Pavel -- Thanks, Sharp! - 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/