gpio: generic: clamp values from bgpio_get_set()

The bgpio_get_set() call should return a value clamped to [0,1],
the current code will return a negative value if reading
bit 31, which turns the value negative as this is a signed value
and thus gets interpreted as an error by the gpiolib core.
Found on the gpio-mxc but applies to any MMIO driver.

Cc: stable@vger.kernel.org # 4.3+
Cc: kernel@pengutronix.de
Cc: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Fixes:  e20538b82f1f ("gpio: Propagate errors from chip->get()")
Reported-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-generic.c b/drivers/gpio/gpio-generic.c
index bd5193c67a9c272cb0bebf779ce3277d22aac479..88ae70ddb1274b11f31bad5dcb344d3a57f9c6e3 100644 (file)
--- a/drivers/gpio/gpio-generic.c
+++ b/drivers/gpio/gpio-generic.c
@@ -141,9 +141,9 @@ static int bgpio_get_set(struct gpio_chip *gc, unsigned int gpio)
        unsigned long pinmask = bgc->pin2mask(bgc, gpio);
 
        if (bgc->dir & pinmask)
-               return bgc->read_reg(bgc->reg_set) & pinmask;
+               return !!(bgc->read_reg(bgc->reg_set) & pinmask);
        else
-               return bgc->read_reg(bgc->reg_dat) & pinmask;
+               return !!(bgc->read_reg(bgc->reg_dat) & pinmask);
 }
 
 static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)