linux-kernel - Re: [PATCH v4 1/2] gpio: gpio-mlxbf3: Add gpio driver support

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Date:   Fri, 24 Feb 2023 11:47:43 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Asmaa Mnebhi <asmaa@...dia.com>
Cc:     "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] gpio: gpio-mlxbf3: Add gpio driver support

On Fri, Feb 24, 2023 at 12:51 AM Asmaa Mnebhi <asmaa@...dia.com> wrote:

...

> > > > > Ah that’s my bad. The property should be called "ngpios" like in
> > > > > the DT
> > > > documentation. Will fix.
> > > >
> > > > And why do you need it? What's a corner case that the GPIO library
> > > > doesn't handle yet?
> > >
> > > We have 2 gpiochips, gpiochip 0 supports 32 gpio pins and gpiochip 1
> > supports only 24 pins.
> > > If I remove the logic from gpio-mlxbf3.c, the gpiolib.c logic will correctly set
> > the ngpios = 32 for gpiochip 0 but will wrongly set ngpios=32 for gpiogchip 1:
> >
> > So, either you need to have two entries in DT per chip or ngpios should be 56.
> >
> I already have 2 entries in my ACPI table, in the first entry, ngpios = 32 and in the second entry ngpios = 24.

Can you show the DSDT excerpt of this device? (Also including the
pieces for pin control)

Is this a table of the device in the wild?

> Gpiochip_add_data_with_keys only reads the ngpios property if (ngpios == 0) which is not the case when
> bgpio_init is called. bgpio_init uses "sz" argument to populate the ngpio in bgpio_init, which is not what we want.

Maybe bgpio_init() is not a good API for your case?

--
With Best Regards,
Andy Shevchenko