Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752043AbaKQJJV (ORCPT ); Mon, 17 Nov 2014 04:09:21 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:42003 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751768AbaKQJJT (ORCPT ); Mon, 17 Nov 2014 04:09:19 -0500 Date: Mon, 17 Nov 2014 10:09:15 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Alexandre Courbot Cc: Grant Likely , Linus Walleij , linux-kernel@vger.kernel.org, Alexandre Courbot Subject: Re: [PATCH 2/4] gpiolib: use const parameters when possible Message-ID: <20141117090915.GE27002@pengutronix.de> References: <1360738983-22436-1-git-send-email-gnurou@gmail.com> <1360738983-22436-3-git-send-email-gnurou@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1360738983-22436-3-git-send-email-gnurou@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 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 Hello, On Wed, Feb 13, 2013 at 04:03:00PM +0900, Alexandre Courbot wrote: > From: Alexandre Courbot > > Constify descriptor parameter of gpiod_* functions for those that > should obviously not modify it. This includes value or direction get, > cansleep, and IRQ number query. > > Signed-off-by: Alexandre Courbot This patch is applied as def634338d3ffb32fbe9b0a2d70cc24ef909cd4f since v3.9-rc2. > drivers/gpio/gpiolib.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index 8a2cf9c..ad6df6b 100644 > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -207,7 +208,7 @@ static int gpiochip_find_base(int ngpio) > } > > /* caller ensures gpio is valid and requested, chip->get_direction may sleep */ > -static int gpiod_get_direction(struct gpio_desc *desc) > +static int gpiod_get_direction(const struct gpio_desc *desc) > { > struct gpio_chip *chip; > unsigned offset; > @@ -223,11 +224,13 @@ static int gpiod_get_direction(struct gpio_desc *desc) > if (status > 0) { > /* GPIOF_DIR_IN, or other positive */ > status = 1; > - clear_bit(FLAG_IS_OUT, &desc->flags); > + /* FLAG_IS_OUT is just a cache of the result of get_direction(), > + * so it does not affect constness per se */ > + clear_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags); I think this is worse than not having gpiod_get_direction take a const descriptor. I don't know an example for this particular case where this could break, but usually casting away a const is bad and can break in various ways. Maybe even drop the public function gpiod_get_direction completely. As of next-20141114 there are only two users of this function (apart from drivers/gpio/gpiolib*) and both are wrong (as discussed in http://thread.gmane.org/gmane.linux.serial/16808/focus=4783). 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/