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

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Message-ID: <CH2PR12MB389530C5929100CB54396CF5D7AB9@CH2PR12MB3895.namprd12.prod.outlook.com>
Date:   Thu, 23 Feb 2023 22:51:50 +0000
From:   Asmaa Mnebhi <asmaa@...dia.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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


> >
> > > > > +       npins = MLXBF3_GPIO_MAX_PINS_PER_BLOCK;
> > > > > +       device_property_read_u32(dev, "npins", &npins);
> > > >
> > > > I don't see DT bindings for this property (being added in this
> > > > series). Is it
> > > already established one?
> > > >
> > > > 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.
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.