Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751787Ab1CFHaK (ORCPT ); Sun, 6 Mar 2011 02:30:10 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:63780 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360Ab1CFHaG (ORCPT ); Sun, 6 Mar 2011 02:30:06 -0500 Date: Sun, 6 Mar 2011 00:30:03 -0700 From: Grant Likely To: Peter Tyser Cc: linux-kernel@vger.kernel.org, Alek Du , Samuel Ortiz , David Brownell , Eric Miao , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Mark Brown , Joe Perches , Alan Cox Subject: Re: [PATCH v5 2/4] gpiolib: Add ability to get GPIO direction Message-ID: <20110306073003.GA29325@angua.secretlab.ca> References: <1299022100-14564-1-git-send-email-ptyser@xes-inc.com> <1299022100-14564-2-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: <1299022100-14564-2-git-send-email-ptyser@xes-inc.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4597 Lines: 125 On Tue, Mar 01, 2011 at 05:28:18PM -0600, Peter Tyser wrote: > Add a new get_direction() function to the gpio_chip structure. This is > useful so that the direction of a GPIO can be determined when its > initially exported. Previously, the direction defaulted to "unknown" > regardless of the actual configuration of the GPIO. > > If a GPIO driver implements get_direction(), it is called in > gpio_request() to set the initial direction of the GPIO accurately. I don't like this approach. It effectively creates two methods for determining the direction of a gpio; either ask the driver, or read the flags value. Currently, only gpio_request() actually uses the first option, but it still leaves the ambiguity. Instead, the driver should be able to preload the direction flag at or shortly after gpiochip_add() time. No need for a new callback hook from what I can see. g. > > 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 > > Changes since v3: > - Removed "pin" references from the commit message > - Added might_sleep() call > - Made the direction always be set in gpio_request() > > Change since V4: > - None > > drivers/gpio/gpiolib.c | 25 +++++++++++++++++++++++++ > include/asm-generic/gpio.h | 4 ++++ > 2 files changed, 29 insertions(+), 0 deletions(-) > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index eb74311..106164f 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 = -1; /* Default to unknown direction */ > unsigned long flags; > > spin_lock_irqsave(&gpio_lock, flags); > @@ -1214,6 +1215,30 @@ 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); > + 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; > + } > + > done: > if (status) > pr_debug("gpio_request: gpio-%d (%s) status %d\n", > diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h > index ff5c660..6af5a3e 100644 > --- a/include/asm-generic/gpio.h > +++ b/include/asm-generic/gpio.h > @@ -57,6 +57,8 @@ struct device_node; > * @direction_input: configures signal "offset" as input, or returns error > * @get: returns value for signal "offset"; for output signals this > * returns either the value actually sensed, or zero > + * @get_direction: optional hook to determine if a GPIO signal is configured > + * as an input, output, or unknown > * @direction_output: configures signal "offset" as output, or returns error > * @set: assigns output value for signal "offset" > * @to_irq: optional hook supporting non-static gpio_to_irq() mappings; > @@ -101,6 +103,8 @@ struct gpio_chip { > unsigned offset); > int (*get)(struct gpio_chip *chip, > unsigned offset); > + int (*get_direction)(struct gpio_chip *chip, > + unsigned offset); > int (*direction_output)(struct gpio_chip *chip, > unsigned offset, int value); > int (*set_debounce)(struct gpio_chip *chip, > -- > 1.7.0.4 > -- 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/