gpio: remove const modifier from gpiod_get_direction()

Although gpiod_get_direction() can be considered side-effect free for
consumers, its internals involve setting or clearing bits in the
affected GPIO descriptor, for which we need to force-cast the const
descriptor variable to non-const. This could lead to incorrect behavior
if the compiler decides to optimize here, so remove this const
attribute. The intent is to make gpiod_get_direction() private anyway,
so it does not really matter.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 4 insertions, 6 deletions

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 781fbed00fc3..2ac1800b58bb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -41,7 +41,7 @@ static DEFINE_MUTEX(sysfs_lock);
 static ssize_t gpio_direction_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        const struct gpio_desc  *desc = dev_get_drvdata(dev);
+        struct gpio_desc        *desc = dev_get_drvdata(dev);
         ssize_t                 status;
 
         mutex_lock(&sysfs_lock);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5619922ebf44..0b271ef87c09 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -148,7 +148,7 @@ static int gpiochip_find_base(int ngpio)
  *
  * This function may sleep if gpiod_cansleep() is true.
  */
-int gpiod_get_direction(const struct gpio_desc *desc)
+int gpiod_get_direction(struct gpio_desc *desc)
 {
         struct gpio_chip        *chip;
         unsigned                offset;
@@ -164,13 +164,11 @@ int gpiod_get_direction(const struct gpio_desc *desc)
         if (status > 0) {
                 /* GPIOF_DIR_IN, or other positive */
                 status = 1;
-                /* FLAG_IS_OUT is just a cache of the result of get_direction(),
-                 * so it does not affect constness per se */
-                clear_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+                clear_bit(FLAG_IS_OUT, &desc->flags);
         }
         if (status == 0) {
                 /* GPIOF_DIR_OUT */
-                set_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+                set_bit(FLAG_IS_OUT, &desc->flags);
         }
         return status;
 }