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@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 41 insertions, 2 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d5f9742d9ac1..e468eed261c5 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");
@@ -1080,6 +1108,7 @@ 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
@@ -1231,9 +1260,15 @@ 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",
@@ -1769,6 +1804,7 @@ 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 a9432fc6b8ba..eb70ca295971 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
@@ -100,7 +102,8 @@ 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,