linux-kernel - Re: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate funcs from get

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Message-ID: <a94c375a-baf9-4530-8425-762dc9adf35e@samsung.com>
Date: Wed, 19 Feb 2025 12:16:21 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Bartosz Golaszewski <brgl@...ev.pl>, Linus Walleij
	<linus.walleij@...aro.org>, Florian Fainelli
	<florian.fainelli@...adcom.com>, Ray Jui <rjui@...adcom.com>, Scott Branden
	<sbranden@...adcom.com>, Broadcom internal kernel review list
	<bcm-kernel-feedback-list@...adcom.com>, Stefan Wahren <wahrenst@....net>,
	Liao Chen <liaochen4@...wei.com>, Chen-Yu Tsai <wens@...e.org>, Mark Brown
	<broonie@...nel.org>
Cc: linux-gpio@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Bartosz
	Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate
 funcs from get_direction()

On 19.02.2025 11:27, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> 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@...nel.org>
> Closes: https://lore.kernel.org/all/Z7VFB1nST6lbmBIo@finisterre.sirena.org.uk/
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Closes: 
https://lore.kernel.org/all/dfe03f88-407e-4ef1-ad30-42db53bbd4e4@samsung.com/
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>   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