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

Peter Tyser
2011-03-01T23:29:12Z

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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