linux-kernel - Re: [PATCH v4 2/2] gpiolib: check the 'ngpios' property in core gpiolib code

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Message-ID: <CAMRc=MfYKscNMbGqwj6os_SmXhBBqUMWJCwu0K0xO+VZ0vvNfA@mail.gmail.com>
Date:   Thu, 2 Dec 2021 16:48:20 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Johan Hovold <johan@...nel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] gpiolib: check the 'ngpios' property in core
 gpiolib code

On Thu, Dec 2, 2021 at 4:38 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Thu, Dec 02, 2021 at 02:40:34PM +0100, Bartosz Golaszewski wrote:
> > Several drivers read the 'ngpios' device property on their own, but
> > since it's defined as a standard GPIO property in the device tree bindings
> > anyway, it's a good candidate for generalization. If the driver didn't
> > set its gc->ngpio, try to read the 'ngpios' property from the GPIO
> > device's firmware node before bailing out.
>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> One nit-pick below (you may amend it when applying)
>
> > Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
> > Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> > ---
> > v1 -> v2:
> > - use device_property_read_u32() instead of fwnode_property_read_u32()
> > - reverse the error check logic
> >
> > v2 -> v3:
> > - don't shadow errors other than -ENODATA in device_property_read_u32()
> >
> > v3 -> v4:
> > - also make sure we return -EINVAL when the device 'ngpios' property is
> >   set to 0 (thanks Andy!)
> >
> >  drivers/gpio/gpiolib.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index ede8b8a7aa18..bd9b8cb53476 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -599,6 +599,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
> >       int base = gc->base;
> >       unsigned int i;
> >       int ret = 0;
> > +     u32 ngpios;
> >
> >       /*
> >        * First: allocate and populate the internal stat container, and
> > @@ -646,6 +647,26 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
> >               goto err_free_dev_name;
> >       }
> >
> > +     /*
> > +      * Try the device properties if the driver didn't supply the number
> > +      * of GPIO lines.
> > +      */
> > +     if (gc->ngpio == 0) {
> > +             ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
> > +             if (ret == -ENODATA)
> > +                     /*
> > +                      * -ENODATA means that there is no property found and
> > +                      * we want to issue the error message to the user.
> > +                      * Besides that, we want to return different error code
> > +                      * to state that supplied value is not valid.
>
> > +                      * */
>
> First '* ' is not needed.
>

I'll fix it when applying.

Bart