linux-kernel - Re: [PATCH RFT/RFC 1/2] gpiolib: support "undefined" GPIO machine lookup

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Message-ID: <CAMRc=MeD4gsyHe_rkGRgRO4p36+szobgCnc0C-CYGWZhm-dQNQ@mail.gmail.com>
Date: Wed, 19 Nov 2025 17:49:31 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	David Rhodes <david.rhodes@...rus.com>, Richard Fitzgerald <rf@...nsource.cirrus.com>, 
	Lee Jones <lee@...nel.org>, Mark Brown <broonie@...nel.org>, 
	Maciej Strozek <mstrozek@...nsource.cirrus.com>, 
	Charles Keepax <ckeepax@...nsource.cirrus.com>, Andy Shevchenko <andy@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-sound@...r.kernel.org, patches@...nsource.cirrus.com, 
	linux-spi@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH RFT/RFC 1/2] gpiolib: support "undefined" GPIO machine lookup

On Wed, Nov 19, 2025 at 4:21 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> SPI devices can specify a cs-gpios property to enumerate their chip
> selects. In device tree, a zero entry in this property can be used to
> specify that a particular chip select is using the SPI controllers
> native chip select, for example:
>
>     cs-gpios = <&gpio1 0 0>, <0>;
>
> Here, the second chip select is native. Allow users to pass
> ERR_PTR(-ENOENT) as the key field in struct gpiod_lookup, indicating a
> native chip select.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  drivers/gpio/gpiolib.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 91e0c384f34ae5c0ed61ccd3a978685d4f72e867..dbb5f7fe7b661979f559fcd32ad6e1c463431a18 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -4557,6 +4557,9 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
>                 if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
>                         continue;
>
> +               if (p->key == PTR_ERR(-ENOENT))

As the build bot pointed out - this should have been ERR_PTR(-ENOENT).

Bart

> +                       return ERR_PTR(-ENOENT);
> +
>                 if (p->chip_hwnum == U16_MAX) {
>                         desc = gpio_name_to_desc(p->key);
>                         if (desc) {
>
> --
> 2.51.0
>