gpiolib: of: fix bounds check for 'gpio-reserved-ranges'

commit e75f88efac05bf4e107e4171d8db6d8c3937252d upstream.

Gpiolib interprets the elements of "gpio-reserved-ranges" as "start,size"
because it clears "size" bits starting from the "start" bit in the according
bitmap. So it has to use "greater" instead of "greater or equal" when performs
bounds check to make sure that GPIOs are in the available range.
Previous implementation skipped ranges that include the last GPIO in
the range.

I wrote the mail to the maintainers
(https://lore.kernel.org/linux-gpio/20220412115554.159435-1-andrei.lalaev@emlid.com/T/#u)
of the questioned DTSes (because I couldn't understand how the maintainers
interpreted this property), but I haven't received a response.
Since the questioned DTSes use "gpio-reserved-ranges = <0 4>"
(i.e., the beginning of the range), this patch doesn't affect these DTSes at all.
TBH this patch doesn't break any existing DTSes because none of them
reserve gpios at the end of range.

Fixes: 726cb3ba4969 ("gpiolib: Support 'gpio-reserved-ranges' property")
Signed-off-by: Andrei Lalaev <andrei.lalaev@emlid.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 3ece59185d372b7d6b67e23ecfd3f425b9a1bde2..b1dcd2dd52e6b2b2d79f4445d205bf7120767958 100644 (file)
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -783,7 +783,7 @@ static void of_gpiochip_init_valid_mask(struct gpio_chip *chip)
                                           i, &start);
                of_property_read_u32_index(np, "gpio-reserved-ranges",
                                           i + 1, &count);
-               if (start >= chip->ngpio || start + count >= chip->ngpio)
+               if (start >= chip->ngpio || start + count > chip->ngpio)
                        continue;
 
                bitmap_clear(chip->valid_mask, start, count);