gpio: make sure gpiod_to_irq() returns negative on NULL desc

commit 54d77198fdfbc4f0fe11b4252c1d9c97d51a3264
("gpio: bail out silently on NULL descriptors")
doesn't work for gpiod_to_irq(): drivers assume that NULL
descriptors will give negative IRQ numbers in return.

It has been pointed out that returning 0 is NO_IRQ and that
drivers should be amended to treat this as an error, but that
is for the longer term: now let us repair the semantics.

Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Reported-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 58d822d..f39bf05 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2056,7 +2056,14 @@ int gpiod_to_irq(const struct gpio_desc *desc)
        struct gpio_chip *chip;
        int offset;
 
-       VALIDATE_DESC(desc);
+       /*
+        * Cannot VALIDATE_DESC() here as gpiod_to_irq() consumer semantics
+        * requires this function to not return zero on an invalid descriptor
+        * but rather a negative error number.
+        */
+       if (!desc || !desc->gdev || !desc->gdev->chip)
+               return -EINVAL;
+
        chip = desc->gdev->chip;
        offset = gpio_chip_hwgpio(desc);
        if (chip->to_irq) {