Re: [PATCH v2] gpio: mt7621: support gpio-line-names property

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Sat, Jul 3, 2021 at 3:51 PM Sergio Paracuellos
<sergio.paracuellos@xxxxxxxxx> wrote:
> On Sat, Jul 3, 2021 at 2:05 PM Sergio Paracuellos
> <sergio.paracuellos@xxxxxxxxx> wrote:
> > On Sat, Jul 3, 2021 at 1:32 PM Andy Shevchenko
> > <andy.shevchenko@xxxxxxxxx> wrote:
> > > On Sat, Jul 3, 2021 at 2:06 PM Sergio Paracuellos
> > > <sergio.paracuellos@xxxxxxxxx> wrote:
> > > > On Fri, Jul 2, 2021 at 1:30 PM Sergio Paracuellos
> > > > <sergio.paracuellos@xxxxxxxxx> wrote:
> > >
> > > ...
> > >
> > > > -               ret = devprop_gpiochip_set_names(gc);
> > > > +               ret = devprop_gpiochip_set_names(gc, 0);
> > >
> > > I had been expecting that this parameter would be in the field of the gpiochip.
> > >
> > > ...
> >
> > If doing it in that way is preferred, I have no problem at all. But in
> > that case I think there is no need for a new
> > 'devprop_gpiochip_set_names_base' and we can assume for all drivers to
> > be zero and if is set taking it into account directly in
> > devprop_gpiochip_set_names function? Is this what you mean by having
> > this field added there??

The below is closer to what I meant, yes. I have not much time to look
into the details, but I don't have objections about what you suggested
below. Additional comments there as well.

> How about something like this?
>
> diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
> index 82fb20dca53a..5854a9343491 100644
> --- a/drivers/gpio/gpio-mt7621.c
> +++ b/drivers/gpio/gpio-mt7621.c
> @@ -241,6 +241,7 @@ mediatek_gpio_bank_probe(struct device *dev,
>         if (!rg->chip.label)
>                 return -ENOMEM;
>
> +       rg->chip.offset = bank * MTK_BANK_WIDTH;
>         rg->irq_chip.name = dev_name(dev);
>         rg->irq_chip.parent_device = dev;
>         rg->irq_chip.irq_unmask = mediatek_gpio_irq_unmask;

Obviously it should be a separate patch :-)

> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 6e3c4d7a7d14..0587f46b7c22 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -380,10 +380,10 @@ static int devprop_gpiochip_set_names(struct
> gpio_chip *chip)
>                 return 0;
>
>         count = device_property_string_array_count(dev, "gpio-line-names");
> -       if (count < 0)

> +       if (count < 0 || count <= chip->offset)

Please, split it into two conditionals and add a comment to the second one.

>                 return 0;
>
> -       if (count > gdev->ngpio) {
> +       if (count > gdev->ngpio && chip->offset == 0) {
>                 dev_warn(&gdev->dev, "gpio-line-names is length %d but
> should be at most length %d",
>                          count, gdev->ngpio);
>                 count = gdev->ngpio;
> @@ -401,8 +401,9 @@ static int devprop_gpiochip_set_names(struct
> gpio_chip *chip)
>                 return ret;
>         }
>
> +       count = (chip->offset >= count) ? (chip->offset - count) : count;

Too many parentheses.

>         for (i = 0; i < count; i++)
> -               gdev->descs[i].name = names[i];
> +               gdev->descs[i].name = names[chip->offset + i];
>
>         kfree(names);
>
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index 4a7e295c3640..39e0786586f6 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -312,6 +312,9 @@ struct gpio_irq_chip {
>   *     get rid of the static GPIO number space in the long run.
>   * @ngpio: the number of GPIOs handled by this controller; the last GPIO
>   *     handled is (base + ngpio - 1).
> + * @offset: when multiple gpio chips belong to the same device this
> + *     can be used as offset within the device so friendly names can
> + *     be properly assigned.
>   * @names: if set, must be an array of strings to use as alternative
>   *      names for the GPIOs in this chip. Any entry in the array
>   *      may be NULL if there is no alias for the GPIO, however the
> @@ -398,6 +401,7 @@ struct gpio_chip {
>
>         int                     base;
>         u16                     ngpio;
> +       int                     offset;

u16 (as ngpio has that type)

>         const char              *const *names;
>         bool                    can_sleep;
>
>
> Does this sound reasonable?

> > > > The problem I see with this approach is that
> > > > 'devprop_gpiochip_set_names' already trusts in gpio_device already
> > > > created and this happens in 'gpiochip_add_data_with_key'. So doing in
> > > > this way force "broken drivers" to call this new
> > > > 'devprop_gpiochip_set_names_base' function after
> > > > 'devm_gpiochip_add_data' is called so the core code has already set up
> > > > the friendly names repeated for all gpio chip banks and the approach
> > > > would be to "overwrite" those in a second pass which sounds more like
> > > > a hack than a solution.
> > > >
> > > > But maybe I am missing something in what you were pointing out here.
> > >
> > > Would the above work?

-- 
With Best Regards,
Andy Shevchenko