From 7b61212f2a07a5afd213c8876e52b5c9946441e2 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 2 Sep 2022 14:42:05 +0200 Subject: gpiolib: Get rid of ARCH_NR_GPIOS Since commit 14e85c0e69d5 ("gpio: remove gpio_descs global array") there is no limitation on the number of GPIOs that can be allocated in the system since the allocation is fully dynamic. ARCH_NR_GPIOS is today only used in order to provide downwards gpiobase allocation from that value, while static allocation is performed upwards from 0. However that has the disadvantage of limiting the number of GPIOs that can be registered in the system. To overcome this limitation without requiring each and every platform to provide its 'best-guess' maximum number, rework the allocation to allocate upwards, allowing approx 2 millions of GPIOs. In order to still allow static allocation for legacy drivers, define GPIO_DYNAMIC_BASE with the value 512 as the start for dynamic allocation. The 512 value is chosen because it is the end of the current default range so all current static allocations are expected to be below that value. Of course that's just a rough estimate based on the default value, but assuming static allocations come first, even if there are more static allocations it should fit under the 512 value. In the future, it is expected that all static allocations go away and then dynamic allocation will be patched to start at 0. Signed-off-by: Christophe Leroy Reviewed-by: Andy Shevchenko Signed-off-by: Bartosz Golaszewski --- drivers/gpio/gpiolib.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'drivers/gpio/gpiolib.c') diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 5c64d1a412c7..e8faedca6b14 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -183,14 +183,14 @@ EXPORT_SYMBOL_GPL(gpiod_to_chip); static int gpiochip_find_base(int ngpio) { struct gpio_device *gdev; - int base = ARCH_NR_GPIOS - ngpio; + int base = GPIO_DYNAMIC_BASE; - list_for_each_entry_reverse(gdev, &gpio_devices, list) { + list_for_each_entry(gdev, &gpio_devices, list) { /* found a free space? */ - if (gdev->base + gdev->ngpio <= base) + if (gdev->base >= base + ngpio) break; - /* nope, check the space right before the chip */ - base = gdev->base - ngpio; + /* nope, check the space right after the chip */ + base = gdev->base + gdev->ngpio; } if (gpio_is_valid(base)) { -- cgit