Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030201AbVKCOtY (ORCPT ); Thu, 3 Nov 2005 09:49:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030207AbVKCOtY (ORCPT ); Thu, 3 Nov 2005 09:49:24 -0500 Received: from caramon.arm.linux.org.uk ([212.18.232.186]:29971 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S1030201AbVKCOtX (ORCPT ); Thu, 3 Nov 2005 09:49:23 -0500 Date: Thu, 3 Nov 2005 14:49:04 +0000 From: Russell King To: Pavel Machek Cc: John Lenz , Robert Schwebel , Robert Schwebel , vojtech@suse.cz, rpurdie@rpsys.net, kernel list Subject: Re: best way to handle LEDs Message-ID: <20051103144904.GG28038@flint.arm.linux.org.uk> Mail-Followup-To: Pavel Machek , John Lenz , Robert Schwebel , Robert Schwebel , vojtech@suse.cz, rpurdie@rpsys.net, kernel list 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051103095725.GA703@openzaurus.ucw.cz> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1127 Lines: 31 On Thu, Nov 03, 2005 at 10:57:26AM +0100, Pavel Machek wrote: > 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? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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/