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

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Asmaa Mnebhi <asmaa@nvidia.com>
Cc: "linus.walleij@linaro.org" <linus.walleij@linaro.org>,
	"bgolaszewski@baylibre.com" <bgolaszewski@baylibre.com>,
	"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH v4 1/2] gpio: gpio-mlxbf3: Add gpio driver support
Date: Fri, 24 Feb 2023 11:47:43 +0200	[thread overview]
Message-ID: <CAHp75VfZ1r_sNus_qMYumja3YrJawA6hRHUbi-uPFUprorQ_Kw@mail.gmail.com> (raw)
In-Reply-To: <CH2PR12MB389530C5929100CB54396CF5D7AB9@CH2PR12MB3895.namprd12.prod.outlook.com>

On Fri, Feb 24, 2023 at 12:51 AM Asmaa Mnebhi <asmaa@nvidia.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