Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754526Ab1BRRhM (ORCPT ); Fri, 18 Feb 2011 12:37:12 -0500 Received: from xes-mad.com ([216.165.139.218]:20795 "EHLO xes-mad.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373Ab1BRRhH (ORCPT ); Fri, 18 Feb 2011 12:37:07 -0500 Subject: Re: [PATCH v3 2/4] gpiolib: Add ability to get GPIO pin direction From: Peter Tyser To: Uwe =?ISO-8859-1?Q?Kleine-K=F6nig?= Cc: linux-kernel@vger.kernel.org, Alek Du , Samuel Ortiz , David Brownell , Eric Miao , Mark Brown , Joe Perches , Alan Cox , Grant Likely In-Reply-To: <20110218085734.GX22310@pengutronix.de> References: <1297983799-4747-1-git-send-email-ptyser@xes-inc.com> <1297983799-4747-2-git-send-email-ptyser@xes-inc.com> <20110218085734.GX22310@pengutronix.de> Content-Type: text/plain; charset="UTF-8" Date: Fri, 18 Feb 2011 11:36:26 -0600 Message-ID: <1298050586.965.20444.camel@petert> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4415 Lines: 122 On Fri, 2011-02-18 at 09:57 +0100, Uwe Kleine-König wrote: > On Thu, Feb 17, 2011 at 05:03:17PM -0600, Peter Tyser wrote: > > Add a new get_direction() function to the gpio_chip structure. This is > > useful so that the direction of a pin can be determined when its > > initially exported. Previously, the direction defaulted to "unknown" > > regardless of the actual configuration of the GPIO pin. > > > > If a GPIO driver implements get_direction(), it is called in > > gpio_request() to set the initial direction of the pin accurately. > IMHO the commit log is conceptually wrong, because it talks about a > "pin". Better use gpio here. I don't follow. I used "pin" to make it clear that the get_direction() function operates on a pin-by-pin basis, and to help reduce any ambiguity about if a gpio chip or gpio pin is being referred to. Would you prefer that the "pin" references are clarified to be "GPIO pin"? > > Cc: Alek Du > > Cc: Samuel Ortiz > > Cc: David Brownell > > Cc: Eric Miao > > Cc: Uwe Kleine-K?nig > > Cc: Mark Brown > > Cc: Joe Perches > > Cc: Alan Cox > > Cc: Grant Likely > > Signed-off-by: Peter Tyser > > --- > > Changes since v1: > > - Add support for "unknown" direction > > > > Changes since v2: > > Based on Wolfram's feedback: > > - Use GPIOF_DIR_* flags as returns from get_direction() > > - Call spin_lock_irqsave() to before setting flags > > > > drivers/gpio/gpiolib.c | 23 +++++++++++++++++++++++ > > include/asm-generic/gpio.h | 4 ++++ > > 2 files changed, 27 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > > index eb74311..a656a2c 100644 > > --- a/drivers/gpio/gpiolib.c > > +++ b/drivers/gpio/gpiolib.c > > @@ -1174,6 +1174,7 @@ int gpio_request(unsigned gpio, const char *label) > > struct gpio_desc *desc; > > struct gpio_chip *chip; > > int status = -EINVAL; > > + int dir; > > unsigned long flags; > > > > spin_lock_irqsave(&gpio_lock, flags); > > @@ -1214,6 +1215,28 @@ int gpio_request(unsigned gpio, const char *label) > > } > > } > > > > + if (chip->get_direction) { > > + /* chip->get_direction may sleep */ > > + spin_unlock_irqrestore(&gpio_lock, flags); > might_sleep_if(chip->can_sleep) ? Makes sense. I was following the lead of chip->request() in the same function, which doesn't use might_sleep_if(). I assume might_sleep_if() should be added to it as well in a separate patch? > > + dir = chip->get_direction(chip, gpio - chip->base); > > + spin_lock_irqsave(&gpio_lock, flags); > > + switch (dir) { > > + case GPIOF_DIR_OUT: > > + set_bit(FLAG_DIR_OUT, &desc->flags); > > + clear_bit(FLAG_DIR_IN, &desc->flags); > > + break; > > + case GPIOF_DIR_IN: > > + set_bit(FLAG_DIR_IN, &desc->flags); > > + clear_bit(FLAG_DIR_OUT, &desc->flags); > > + break; > > + default: > > + /* Direction isn't known */ > > + clear_bit(FLAG_DIR_OUT, &desc->flags); > > + clear_bit(FLAG_DIR_IN, &desc->flags); > > + break; > > + } > Alternatively to my suggestion for patch1: > } else { > clear_bit(FLAG_DIR_OUT, &desc->flags); > clear_bit(FLAG_DIR_IN, &desc->flags); I like this way better too. I'll initialize dir = -1 and pull the switch statement out of the conditional, like: if (chip->get_direction) { /* chip->get_direction may sleep */ spin_unlock_irqrestore(&gpio_lock, flags); might_sleep_if(chip->can_sleep); dir = chip->get_direction(chip, gpio - chip->base); spin_lock_irqsave(&gpio_lock, flags); } switch (dir) { case GPIOF_DIR_OUT: set_bit(FLAG_DIR_OUT, &desc->flags); clear_bit(FLAG_DIR_IN, &desc->flags); break; case GPIOF_DIR_IN: set_bit(FLAG_DIR_IN, &desc->flags); clear_bit(FLAG_DIR_OUT, &desc->flags); break; default: /* Direction isn't known */ clear_bit(FLAG_DIR_OUT, &desc->flags); clear_bit(FLAG_DIR_IN, &desc->flags); break; } Thanks for the comments, Peter -- 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/