linux-kernel - Re: [PATCH v3 2/4] gpio: Add GPIO driver for Nintendo Wii

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Message-ID: <20180209165858.ebm7ed7f4b5uakju@latitude>
Date:   Fri, 9 Feb 2018 17:58:58 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Neuschäfer <j.neuschaefer@....net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joel Stanley <joel@....id.au>,
        "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT" 
        <linuxppc-dev@...ts.ozlabs.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Albert Herranz <albert_herranz@...oo.es>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3 2/4] gpio: Add GPIO driver for Nintendo Wii

On Fri, Feb 09, 2018 at 05:30:55PM +0200, Andy Shevchenko wrote:
> On Fri, Feb 9, 2018 at 2:07 PM, Jonathan Neuschäfer
> <j.neuschaefer@....net> wrote:
> > The Nintendo Wii's chipset (called "Hollywood") has a GPIO controller
> > that supports a configurable number of pins (up to 32), interrupts, and
> > some special mechanisms to share the controller between the system's
> > security processor (an ARM926) and the PowerPC CPU. Pin multiplexing is
> > not supported.
> >
> > This patch adds a basic driver for this GPIO controller. Interrupt
> > support will come in a later patch.
> >
> > This patch is based on code developed by Albert Herranz and the GameCube
> > Linux Team, file arch/powerpc/platforms/embedded6xx/hlwd-gpio.c,
> > available at https://github.com/DeltaResero/GC-Wii-Linux-Kernels, but
> > has grown quite dissimilar.
> >
> 
> Fine to me, though one comment below.
> In any case,
> 
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

Thank you.


[...]
> > diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> > index d6a8e851ad13..47606dfe06cc 100644
> > --- a/drivers/gpio/Kconfig
> > +++ b/drivers/gpio/Kconfig
> > @@ -229,6 +229,15 @@ config GPIO_GRGPIO
> >           Select this to support Aeroflex Gaisler GRGPIO cores from the GRLIB
> >           VHDL IP core library.
> >
> > +config GPIO_HLWD
> > +       tristate "Nintendo Wii (Hollywood) GPIO"
> 
> > +       depends on OF_GPIO
> 
> You may get rid of it if...

[ Even if this driver isn't switched to the unified device property API,
  I think "depends on OF" would be enough here, because it doesn't use
  the code that's guarded by CONFIG_OF_GPIO (gpiolib-of.c), but this
  applies to other drivers (e.g. gpio-aspeed, gpio-bcm-kona) as well, so
  this would ideally be a bigger cleanup patch. ]


> > +       res = of_property_read_u32(pdev->dev.of_node, "ngpios", &ngpios);
> 
> ...if you switch to unified device property API.

I don't think this change is worth making, unless/until the of_property
API is deprecated. I'm rather sure this GPIO controller won't appear in
an ACPI-based system.


Thanks,
Jonathan Neuschäfer

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