Parse the list of chips to find the descriptor corresponding to a GPIO number instead of directly picking the entry of the global gpio_desc[] array, which is due to be removed.
This turns the complexity of converting a GPIO number into a descriptor from O(1) to O(n) where n is the number of GPIO chips in the system. Since n is ought to be small anyway, there should be no noticeable performance impact. Moreover, GPIO users who care for speed already have implemented their own gpio_get_value() and gpio_set_value() with a fast path for the GPIO numbers that matter and this change does not affect such use cases. The descriptor-based GPIO API, due to be introduced soon, will make this lookup unnecessary. Signed-off-by: Alexandre Courbot <[email protected]> --- drivers/gpio/gpiolib.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 9599b9a..0247c48 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -122,10 +122,21 @@ static int gpio_chip_hwgpio(const struct gpio_desc *desc) */ static struct gpio_desc *gpio_to_desc(unsigned gpio) { - if (WARN(!gpio_is_valid(gpio), "invalid GPIO %d\n", gpio)) - return NULL; - else - return &gpio_desc[gpio]; + struct gpio_chip *chip; + + list_for_each_entry(chip, &gpio_chips, list) { + int gpio_min = chip->base; + int gpio_max = gpio_min + chip->ngpio; + if (gpio >= gpio_min && gpio < gpio_max) + return &chip->desc[gpio - gpio_min]; + else if (gpio < gpio_min) + /* gpio_chips are ordered by base, so we won't get any + * hit if we arrive here... */ + break; + } + + pr_warn("%s: no registered chip to handle GPIO %d\n", __func__, gpio); + return NULL; } /** -- 1.8.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
