linux-kernel - Re: [PATCH] gpiolib: don't bail out if get_direction() fails in gpiochip_add

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Message-ID: <22224aa7-3af6-46f3-8d45-ddb8e5829fc5@samsung.com>
Date: Thu, 20 Feb 2025 10:17:14 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Bartosz Golaszewski <brgl@...ev.pl>, Linus Walleij
	<linus.walleij@...aro.org>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, Bartosz
	Golaszewski <bartosz.golaszewski@...aro.org>, Mark Brown
	<broonie@...nel.org>
Subject: Re: [PATCH] gpiolib: don't bail out if get_direction() fails in
 gpiochip_add_data()

On 19.02.2025 15:43, 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. Some drivers have been
> observed to fail to register now as they may call get_direction() in
> gpiochip_add_data() in contexts where it has always silently failed.
> Until we audit all drivers, replace the bail-out to a kernel log
> warning.
>
> 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/
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Closes: https://lore.kernel.org/all/dfe03f88-407e-4ef1-ad30-42db53bbd4e4@samsung.com/
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

This fixes the issue observed on RPi boards without any changes to 
gpio/pinctrl driver.

> ---
>   drivers/gpio/gpiolib.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 704452fd94bb..48cf1bb23e24 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1060,7 +1060,15 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) {
>   			ret = gc->get_direction(gc, desc_index);
>   			if (ret < 0)
> -				goto err_cleanup_desc_srcu;
> +				/*
> +				 * FIXME: Bail-out here once all GPIO drivers
> +				 * are updated to not return errors in
> +				 * situations that can be considered normal
> +				 * operation.
> +				 */
> +				dev_warn(&gdev->dev,
> +					 "%s: get_direction failed: %d\n",
> +					 __func__, ret);
>   
>   			assign_bit(FLAG_IS_OUT, &desc->flags, !ret);
>   		} else {

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