Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754911Ab1BQLFx (ORCPT ); Thu, 17 Feb 2011 06:05:53 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:47678 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859Ab1BQLFv (ORCPT ); Thu, 17 Feb 2011 06:05:51 -0500 Date: Thu, 17 Feb 2011 12:05:47 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Eric Miao Cc: Peter Tyser , linux-kernel@vger.kernel.org, Alek Du , Samuel Ortiz , David Brownell , Mark Brown , Joe Perches , Alan Cox , Grant Likely Subject: Re: [PATCH v2 1/4] gpiolib: Add "unknown" direction support Message-ID: <20110217110547.GN22310@pengutronix.de> References: <1297904216-15219-1-git-send-email-ptyser@xes-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:215:17ff:fe12:23b0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1456 Lines: 30 On Thu, Feb 17, 2011 at 03:33:42PM +0800, Eric Miao wrote: > On Thu, Feb 17, 2011 at 8:56 AM, Peter Tyser wrote: > > Previously, gpiolib would unconditionally flag all GPIO pins as inputs, > > regardless of their true state. ?This resulted in all GPIO output pins > > initially being incorrectly identified as "input" in the GPIO sysfs. > > > > Since the direction of GPIOs is not known prior to having their > > direction set, instead set the default direction to "unknown" to prevent > > user confusion. ?A pin with an "unknown" direction can not be written or > > read via sysfs; it must first be configured as an input or output before > > it can be used. > > > > Hrm... that's why I don't like the original definition of gpio_request() > which is vague on the pin configurations. The pin configuration should > be clear upon requesting, otherwise it's a potential issue. I don't know (state: "unknown" :-) what you would prefer here. An implicit gpio_direction_input()? Or gpio_reserve_and_direction_input()? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | -- 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/