linux-kernel - [PATCH v2 2/4] gpiolib: Add ability to get GPIO pin direction

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Date:	Wed, 16 Feb 2011 18:56:54 -0600
From:	Peter Tyser <ptyser@...-inc.com>
To:	linux-kernel@...r.kernel.org
Cc:	Peter Tyser <ptyser@...-inc.com>, Alek Du <alek.du@...el.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Eric Miao <eric.y.miao@...il.com>,
	Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Joe Perches <joe@...ches.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: [PATCH v2 2/4] gpiolib: Add ability to get GPIO pin direction

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.

Cc: Alek Du <alek.du@...el.com>
Cc: Samuel Ortiz <sameo@...ux.intel.com>
Cc: David Brownell <dbrownell@...rs.sourceforge.net>
Cc: Eric Miao <eric.y.miao@...il.com>
Cc: Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>
Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Grant Likely <grant.likely@...retlab.ca>
Signed-off-by: Peter Tyser <ptyser@...-inc.com>
---
Changes since v1:
- Add support for "unknown" direction

 drivers/gpio/gpiolib.c     |   20 ++++++++++++++++++++
 include/asm-generic/gpio.h |    4 ++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 0113c10..7723beb 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1214,6 +1214,26 @@ int gpio_request(unsigned gpio, const char *label)
 		}
 	}
 
+	if (chip->get_direction) {
+		/* chip->get_direction may sleep */
+		spin_unlock_irqrestore(&gpio_lock, flags);
+		switch (chip->get_direction(chip, gpio - chip->base)) {
+		case -1:
+			clear_bit(FLAG_DIR_OUT, &desc->flags);
+			clear_bit(FLAG_DIR_IN, &desc->flags);
+			break;
+		case 0:
+			set_bit(FLAG_DIR_IN, &desc->flags);
+			clear_bit(FLAG_DIR_OUT, &desc->flags);
+			break;
+		case 1:
+			set_bit(FLAG_DIR_OUT, &desc->flags);
+			clear_bit(FLAG_DIR_IN, &desc->flags);
+			break;
+		}
+		spin_lock_irqsave(&gpio_lock, flags);
+	}
+
 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 (0) or output (1), or unknown (-1)
  * @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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