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 12:20:57 +0000
From: Bough Chen <haibo.chen@....com>
To: Linus Walleij <linus.walleij@...aro.org>
CC: "brgl@...ev.pl" <brgl@...ev.pl>, "linux-gpio@...r.kernel.org"
	<linux-gpio@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [PATCH] gpio: vf610: always set GPIO to input mode when used as
 interrupt source

> -----Original Message-----
> From: Linus Walleij <linus.walleij@...aro.org>
> Sent: 2024年4月23日 19:41
> To: Bough Chen <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.

Thanks for your quick review, I will do that in V2.

> 
> 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.

Yes, will implement gc->get_direction(), if we did this before, then for this case we meet, framework will print out error log, save much debug time. 

Best Regards
Haibo Chen 
> 
> Yours,
> Linus Walleij