linux-kernel - Re: [PATCH 2/2] gpio: mxc: switch to dynamic allocat GPIO base

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Date:   Fri, 26 May 2023 15:12:44 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     haibo.chen@....com
Cc:     linus.walleij@...aro.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-imx@....com,
        christophe.leroy@...roup.eu
Subject: Re: [PATCH 2/2] gpio: mxc: switch to dynamic allocat GPIO base

On Sat, May 6, 2023 at 10:56 AM <haibo.chen@....com> wrote:
>
> From: Haibo Chen <haibo.chen@....com>
>
> gpiolib want to get completely rid of static gpiobase allocation,
> so switch to dynamic allocat GPIO base, also can avoid warning
> message:
>
> [    1.529974] gpio gpiochip0: Static allocation of GPIO base
> is deprecated, use dynamic allocation.
>
> Signed-off-by: Haibo Chen <haibo.chen@....com>
> ---
>  drivers/gpio/gpio-mxc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-mxc.c b/drivers/gpio/gpio-mxc.c
> index 9d0cec4b82a3..abc129a88a62 100644
> --- a/drivers/gpio/gpio-mxc.c
> +++ b/drivers/gpio/gpio-mxc.c
> @@ -462,8 +462,7 @@ static int mxc_gpio_probe(struct platform_device *pdev)
>         port->gc.request = gpiochip_generic_request;
>         port->gc.free = gpiochip_generic_free;
>         port->gc.to_irq = mxc_gpio_to_irq;
> -       port->gc.base = (pdev->id < 0) ? of_alias_get_id(np, "gpio") * 32 :
> -                                            pdev->id * 32;
> +       port->gc.base = -1;
>
>         err = devm_gpiochip_add_data(&pdev->dev, &port->gc, port);
>         if (err)
> --
> 2.34.1
>

This is not the first time we're seeing someone submit this fix[1].

Unfortunately it's been brought to our attention that this breaks
existing user-space scripts that rely on fixed GPIO numbering in
sysfs.

Bart

[1] https://lore.kernel.org/lkml/CACRpkdYV3mHNYvBg1nf+12Q2XZH_g4iTrA2YB1SVQ=ROriRRgg@mail.gmail.com/T/