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    Subject[PATCH v5 2/4] gpiolib: Add ability to get GPIO direction
    Date
    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.

    Cc: Alek Du <alek.du@intel.com>
    Cc: Samuel Ortiz <sameo@linux.intel.com>
    Cc: David Brownell <dbrownell@users.sourceforge.net>
    Cc: Eric Miao <eric.y.miao@gmail.com>
    Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
    Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
    Cc: Joe Perches <joe@perches.com>
    Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
    Cc: Grant Likely <grant.likely@secretlab.ca>
    Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
    ---
    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
    --
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