[PATCH] gpio: clamp returned values to the boolean range

[Alexandre Courbot <acourbot@nvidia.com>]

Nothing prevents GPIO drivers from returning values outside the
boolean range, and as it turns out a few drivers are actually doing so.
These values were passed as-is to unsuspecting consumers and created
confusion.

This patch makes the internal _gpiod_get_raw_value() function return a
bool, effectively clamping the GPIO value to the boolean range no
matter what the driver does.

While we are at it, we also change the value parameter of
_gpiod_set_raw_value() to bool type before drivers start doing funny
things with non-boolean values.

Another way to fix this would be to change the prototypes of the driver
interface to use bool directly, but this would require a huge
cross-systems patch so this simpler solution is preferred.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
This issue was discussed some time ago already
(https://www.mail-archive.com/linux-gpio@vger.kernel.org/msg02019.html),
here is finally the fix for it. Not exactly what we planned but who would
take a hundreds-lines change when a two-liner does the same?

 drivers/gpio/gpiolib.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 50c4922fe53a..45cefccbf4bf 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1928,7 +1928,7 @@ EXPORT_SYMBOL_GPL(gpiod_is_active_low);
  * that the GPIO was actually requested.
  */
 
-static int _gpiod_get_raw_value(const struct gpio_desc *desc)
+static bool _gpiod_get_raw_value(const struct gpio_desc *desc)
 {
 	struct gpio_chip	*chip;
 	int value;
@@ -2041,7 +2041,7 @@ static void _gpio_set_open_source_value(struct gpio_desc *desc, int value)
 			  __func__, err);
 }
 
-static void _gpiod_set_raw_value(struct gpio_desc *desc, int value)
+static void _gpiod_set_raw_value(struct gpio_desc *desc, bool value)
 {
 	struct gpio_chip	*chip;
 
-- 
1.9.0