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 e0f149bdf98ff22638cc1e86bd0915077cbf7592..09999e3e3109eee652903e32c6efc61898a3fddc 100644 (file)
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -525,7 +525,7 @@ 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);