Re: [PATCH] gpio: allocate dynamic gpio numbers top down

[Andrej Picej <andrej.picej@norik.com>]

On 29. 03. 22 10:52, Sascha Hauer wrote:
> For GPIO controllers with dynamic GPIO number bases a free base
> is searched for bottom up. This means that GPIO controllers with
> fixed GPIO numbers must be registered before any controller with
> dynamic GPIO number base is registered, because otherwise the
> GPIO controllers with fixed GPIO numbers find their range occupied
> and can't be registered anymore.
> 
> The probe order normally makes sure the SoC internal GPIO controllers
> with fixed numbers are registered first. With deep probe enabled
> we can't rely on the probe order anymore, so we need another solution.
> 
> With this patch a free GPIO number range is searched for top down
> intead of bottom up, so as long as we have enough space in the
> ARCH_NR_GPIOS range the SoC internal GPIO controllers find their
> base unoccupied. GPIO controllers with dynamic GPIO numbers will
> change their numbers with this patch, but code shouldn't rely on
> these numbers anyway.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Tested on PHYTEC Mira and Nunki board. If you want you can add:
Tested-by: Andrej Picej <andrej.picej@norik.com>

Thanks.
> ---
>   drivers/gpio/gpiolib.c | 26 +++++++++++++-------------
>   1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index f709d11f75..c9b33bcd6c 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -414,22 +414,19 @@ free_array:
>   }
>   EXPORT_SYMBOL(gpio_array_to_id);
>   
> -static int gpiochip_find_base(int start, int ngpio)
> +static int gpiochip_find_base(int ngpio)
>   {
>   	int i;
>   	int spare = 0;
>   	int base = -ENOSPC;
>   
> -	if (start < 0)
> -		start = 0;
> -
> -	for (i = start; i < ARCH_NR_GPIOS; i++) {
> +	for (i = ARCH_NR_GPIOS - 1; i >= 0; i--) {
>   		struct gpio_chip *chip = gpio_desc[i].chip;
>   
>   		if (!chip) {
>   			spare++;
>   			if (spare == ngpio) {
> -				base = i + 1 - ngpio;
> +				base = i;
>   				break;
>   			}
>   		} else {
> @@ -614,14 +611,17 @@ int gpiochip_add(struct gpio_chip *chip)
>   {
>   	int base, i;
>   
> -	base = gpiochip_find_base(chip->base, chip->ngpio);
> -	if (base < 0)
> -		return base;
> -
> -	if (chip->base >= 0 && chip->base != base)
> -		return -EBUSY;
> +	if (chip->base >= 0) {
> +		for (i = 0; i < chip->ngpio; i++) {
> +			if (gpio_desc[chip->base + i].chip)
> +				return -EBUSY;
> +		}
> +	} else {
> +		chip->base = gpiochip_find_base(chip->ngpio);
> +		if (chip->base < 0)
> +			return -ENOSPC;
> +	}
>   
> -	chip->base = base;
>   
>   	list_add_tail(&chip->list, &chip_list);
>   

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