linux-kernel - Re: [RFC v2 10/39] gpio: add HAS

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Date:   Fri, 29 Apr 2022 11:37:18 -0400
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-pci@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [RFC v2 10/39] gpio: add HAS_IOPORT dependencies

On Fri, Apr 29, 2022 at 04:46:00PM +0200, Niklas Schnelle wrote:
> On Fri, 2022-04-29 at 10:32 -0400, William Breathitt Gray wrote:
> > On Fri, Apr 29, 2022 at 03:50:16PM +0200, Niklas Schnelle wrote:
> > > In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
> > > not being declared. We thus need to add HAS_IOPORT as dependency for
> > > those drivers using them.
> > > 
> > > Co-developed-by: Arnd Bergmann <arnd@...nel.org>
> > > Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> > > ---
> > >  drivers/gpio/Kconfig | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> > > index 45764ec3b2eb..14e5998ee95c 100644
> > > --- a/drivers/gpio/Kconfig
> > > +++ b/drivers/gpio/Kconfig
> > > @@ -697,7 +697,7 @@ config GPIO_VR41XX
> > >  
> > >  config GPIO_VX855
> > >  	tristate "VIA VX855/VX875 GPIO"
> > > -	depends on (X86 || COMPILE_TEST) && PCI
> > > +	depends on (X86 || COMPILE_TEST) && PCI && HAS_IOPORT
> > >  	select MFD_CORE
> > >  	select MFD_VX855
> > >  	help
> > > -- 
> > > 2.32.0
> > 
> > I noticed a number of other GPIO drivers make use of inb()/outb() -- for
> > example the PC104 drivers -- should the respective Kconfigs for those
> > drivers also be adjusted here?
> > 
> > William Breathitt Gray
> 
> Good question. As far as I can see most (all?) of these have "select
> ISA_BUS_API" which is "def_bool ISA". Now "config ISA" seems to
> currently be repeated in architectures and doesn't have an explicit
> HAS_IOPORT dependency (it maybe should have one). But it does only make
> sense on architectures with HAS_IOPORT set.

There is such a thing as ISA DMA, but you'll still need to initialize
the device via the IO Port bus first, so perhaps setting HAS_IOPORT for
"config ISA" is the right thing to do: all ISA devices are expected to
communicate in some way via ioport.

William Breathitt Gray

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