Re: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate funcs from get_direction()

[Marek Szyprowski]

On 19.02.2025 11:27, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
>
> Since commit 9d846b1aebbe ("gpiolib: check the return value of
> gpio_chip::get_direction()") we check the return value of the
> get_direction() callback as per its API contract. This driver returns
> -EINVAL if the pin in question is set to one of the alternative
> (non-GPIO) functions. This isn't really an error that should be
> communicated to GPIOLIB so default to returning the "safe" value of
> INPUT in this case. The GPIO subsystem does not have the notion of
> "unknown" direction.
>
> Fixes: 9d846b1aebbe ("gpiolib: check the return value of gpio_chip::get_direction()")
> Reported-by: Mark Brown <broonie@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/Z7VFB1nST6lbmBIo@xxxxxxxxxxxxxxxxxxxxxxxx/
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
Closes: 
https://lore.kernel.org/all/dfe03f88-407e-4ef1-ad30-42db53bbd4e4@xxxxxxxxxxx/
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
>   drivers/pinctrl/bcm/pinctrl-bcm2835.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
> index cc1fe0555e19..eaeec096bc9a 100644
> --- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c
> +++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
> @@ -346,14 +346,14 @@ static int bcm2835_gpio_get_direction(struct gpio_chip *chip, unsigned int offse
>   	struct bcm2835_pinctrl *pc = gpiochip_get_data(chip);
>   	enum bcm2835_fsel fsel = bcm2835_pinctrl_fsel_get(pc, offset);
>   
> -	/* Alternative function doesn't clearly provide a direction */
> -	if (fsel > BCM2835_FSEL_GPIO_OUT)
> -		return -EINVAL;
> +	if (fsel == BCM2835_FSEL_GPIO_OUT)
> +		return GPIO_LINE_DIRECTION_OUT;
>   
> -	if (fsel == BCM2835_FSEL_GPIO_IN)
> -		return GPIO_LINE_DIRECTION_IN;
> -
> -	return GPIO_LINE_DIRECTION_OUT;
> +	/*
> +	 * Alternative function doesn't clearly provide a direction. Default
> +	 * to INPUT.
> +	 */
> +	return GPIO_LINE_DIRECTION_IN;
>   }
>   
>   static void bcm2835_gpio_set(struct gpio_chip *chip, unsigned offset, int value)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland