linux-kernel - Re: [PATCH] gpio: nomadik: Add check for clk

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Message-ID: <CALGdzurLWayryjUEdSy4iuHAgFO=RA=HN=u+BZY96JqESKvi+A@mail.gmail.com>
Date: Mon, 14 Apr 2025 07:11:27 -0500
From: Chenyuan Yang <chenyuan0y@...il.com>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: linus.walleij@...aro.org, brgl@...ev.pl, 
	linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: nomadik: Add check for clk_enable()

On Mon, Apr 14, 2025 at 4:24 AM Théo Lebrun <theo.lebrun@...tlin.com> wrote:
>
> Hello Chenyuan, Linus, Bartosz,
>
> On Sat Apr 12, 2025 at 9:31 PM CEST, Chenyuan Yang wrote:
> > Add check for the return value of clk_enable() to catch
> > the potential error.
> >
> > This is similar to the commit 8332e6670997
> > ("spi: zynq-qspi: Add check for clk_enable()").
> >
> > Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> > Fixes: 966942ae4936 ("gpio: nomadik: extract GPIO platform driver from drivers/pinctrl/nomadik/")
> > ---
> >  drivers/gpio/gpio-nomadik.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/gpio-nomadik.c b/drivers/gpio/gpio-nomadik.c
> > index fa19a44943fd..dbc4cdddf4df 100644
> > --- a/drivers/gpio/gpio-nomadik.c
> > +++ b/drivers/gpio/gpio-nomadik.c
> > @@ -262,8 +262,11 @@ static unsigned int nmk_gpio_irq_startup(struct irq_data *d)
> >  {
> >       struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
> >       struct nmk_gpio_chip *nmk_chip = gpiochip_get_data(gc);
> > +     int ret;
> >
> > -     clk_enable(nmk_chip->clk);
> > +     ret = clk_enable(nmk_chip->clk);
> > +     if (ret)
> > +             return ret;
> >       nmk_gpio_irq_unmask(d);
> >       return 0;
> >  }
>
> Returning a negative value whereas the ->irq_startup() [0] return value
> is an unsigned int? From some quick godbolt testing and briefly reading
> the spec it looks safe to do a round trip (signed->unsigned->signed),
> though not ideal to my eyes.
>
> The caller is __irq_startup() [1].
>
> As for why irq_startup returns an unsigned int, I am unsure. The kernel
> Git history isn't enough to know more. The startup field in struct
> hw_interrupt_type appeared on v2.3.14 [2], so no commit message to
> explain decisions.
>
> Seeing the __irq_startup() code, my proposal would be to turn the return
> value to a signed int, but I haven't exhaustively checked codepaths.

Good catch! I agree that using a signed int could be a better option.

Dear Linus and Bartosz, could you please share your thoughts? If
you’re on board with the change, I’ll go ahead and send a new patch.

> Thanks,
>
> [0]: https://elixir.bootlin.com/linux/v6.13.7/source/include/linux/irq.h#L503
> [1]: https://elixir.bootlin.com/linux/v6.13.7/source/kernel/irq/chip.c#L244
> [2]: https://elixir.bootlin.com/linux/2.3.14/source/include/linux/irq.h#L21
>
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

-Chenyuan