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Message-Id: <1351088727-15257-1-git-send-email-mathias.nyman@linux.intel.com>
Date: Wed, 24 Oct 2012 17:25:27 +0300
From: Mathias Nyman <mathias.nyman@...ux.intel.com>
To: linus.walleij@...ricsson.com
Cc: grant.likely@...retlab.ca, linux-kernel@...r.kernel.org,
Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: [RFC PATCH v2] gpiolib: add gpio get direction callback support
Add .get_direction callback to gpio_chip. This allows gpiolib
to check the current direction of a gpio.
Used to show the correct gpio direction in sysfs and debug entries.
If callback is not set then gpiolib will work as previously;
e.g. guessing everything is input until a direction is set.
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
---
drivers/gpio/gpiolib.c | 38 +++++++++++++++++++++++++++++++++++++-
include/asm-generic/gpio.h | 5 ++++-
2 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index de0213c..141f793 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -191,6 +191,32 @@ err:
return ret;
}
+/* caller ensures gpio is valid and requested, chip->get_direction may sleep */
+static int gpio_get_direction(unsigned gpio)
+{
+ struct gpio_chip *chip;
+ struct gpio_desc *desc = &gpio_desc[gpio];
+ int status = -EINVAL;
+
+ chip = gpio_to_chip(gpio);
+ gpio -= chip->base;
+
+ if (!chip->get_direction)
+ return status;
+
+ status = chip->get_direction(chip, gpio);
+ if (status > 0) {
+ /* GPIOF_DIR_IN, or other positive */
+ status = 1;
+ clear_bit(FLAG_IS_OUT, &desc->flags);
+ }
+ if (status == 0) {
+ /* GPIOF_DIR_OUT */
+ set_bit(FLAG_IS_OUT, &desc->flags);
+ }
+ return status;
+}
+
#ifdef CONFIG_GPIO_SYSFS
/* lock protects against unexport_gpio() being called while
@@ -223,6 +249,7 @@ static ssize_t gpio_direction_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
const struct gpio_desc *desc = dev_get_drvdata(dev);
+ unsigned gpio = desc - gpio_desc;
ssize_t status;
mutex_lock(&sysfs_lock);
@@ -230,6 +257,7 @@ static ssize_t gpio_direction_show(struct device *dev,
if (!test_bit(FLAG_EXPORT, &desc->flags))
status = -EIO;
else
+ gpio_get_direction(gpio);
status = sprintf(buf, "%s\n",
test_bit(FLAG_IS_OUT, &desc->flags)
? "out" : "in");
@@ -1073,6 +1101,7 @@ int gpiochip_add(struct gpio_chip *chip)
* inputs (often with pullups enabled) so power
* usage is minimized. Linux code should set the
* gpio direction first thing; but until it does,
+ * and in case chip->get_direction is not set,
* we may expose the wrong direction in sysfs.
*/
gpio_desc[id].flags = !chip->direction_input
@@ -1224,9 +1253,15 @@ int gpio_request(unsigned gpio, const char *label)
desc_set_label(desc, NULL);
module_put(chip->owner);
clear_bit(FLAG_REQUESTED, &desc->flags);
+ goto done;
}
}
-
+ if (chip->get_direction) {
+ /* chip->get_direction may sleep */
+ spin_unlock_irqrestore(&gpio_lock, flags);
+ gpio_get_direction(gpio);
+ spin_lock_irqsave(&gpio_lock, flags);
+ }
done:
if (status)
pr_debug("gpio_request: gpio-%d (%s) status %d\n",
@@ -1762,6 +1797,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
continue;
+ gpio_get_direction(gpio);
is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
seq_printf(s, " gpio-%-3d (%-20.20s) %s %s",
gpio, gdesc->label,
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 365ea09..d8e8c26 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -56,6 +56,8 @@ struct device_node;
* enabling module power and clock; may sleep
* @free: optional hook for chip-specific deactivation, such as
* disabling module power and clock; may sleep
+ * @get_direction: returns direction for signal "offset", 0=out, 1=in,
+ * (same as GPIOF_DIR_XXX), or negative error
* @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
@@ -98,7 +100,8 @@ struct gpio_chip {
unsigned offset);
void (*free)(struct gpio_chip *chip,
unsigned offset);
-
+ int (*get_direction)(struct gpio_chip *chip,
+ unsigned offset);
int (*direction_input)(struct gpio_chip *chip,
unsigned offset);
int (*get)(struct gpio_chip *chip,
--
1.7.4.1
--
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