linux-kernel - Re: [PATCH] gpio: vf610: always set GPIO to input mode when used as interrupt source

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Date: Tue, 23 Apr 2024 13:40:55 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: haibo.chen@....com
Cc: brgl@...ev.pl, linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	imx@...ts.linux.dev
Subject: Re: [PATCH] gpio: vf610: always set GPIO to input mode when used as
 interrupt source

On Tue, Apr 23, 2024 at 4:28 AM <haibo.chen@....com> wrote:

> From: Haibo Chen <haibo.chen@....com>
>
> Though the default pin configuration is INPUT, but if the prior stage does
> configure the pins as OUTPUT, then Linux will not reconfigure the pin as
> INPUT.
>
> e.g. When use one pin as interrupt source, and set as low level trigger,
> if prior stage already set this pin as OUTPUT low, then will meet interrupt
> storm.
>
> So always set GPIO to input mode when used as interrupt source to fix above
> case.
>
> Signed-off-by: Haibo Chen <haibo.chen@....com>
> ---
>  drivers/gpio/gpio-vf610.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-vf610.c b/drivers/gpio/gpio-vf610.c
> index 07e5e6323e86..305b0bcdee6f 100644
> --- a/drivers/gpio/gpio-vf610.c
> +++ b/drivers/gpio/gpio-vf610.c
> @@ -214,7 +214,7 @@ static int vf610_gpio_irq_set_type(struct irq_data *d, u32 type)
>         else
>                 irq_set_handler_locked(d, handle_edge_irq);
>
> -       return 0;
> +       return port->gc.direction_input(&port->gc, d->hwirq);

Just call vf610_gpio_direction_input() instead of indirecting through
gc->direction_input(), no need to jump through the vtable and as
Bartosz says: it just makes that struct vulnerable.

Second:

In this patch also implement gc->get_direction() which is currently
unimplemented. If you are going to change the direction of a
GPIO randomly at runtime then the framework really likes to
have a chance to know the current direction for obvious reasons.

Yours,
Linus Walleij