linux-kernel - Re: [RFC 12/32] iio: adc: Kconfig: add HAS

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Date:   Tue, 28 Dec 2021 13:50:20 +0100
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        John Garry <john.garry@...wei.com>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [RFC 12/32] iio: adc: Kconfig: add HAS_IOPORT dependencies

On Tue, 2021-12-28 at 11:32 +0100, Geert Uytterhoeven wrote:
> Hi Niklas,
> 
> On Mon, Dec 27, 2021 at 5:53 PM Niklas Schnelle <schnelle@...ux.ibm.com> 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: Arnd Bergmann <arnd@...nel.org>
> > Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> 
> Thanks for your patch!
> 
> > --- a/drivers/iio/adc/Kconfig
> > +++ b/drivers/iio/adc/Kconfig
> > @@ -119,7 +119,7 @@ config AD7606
> > 
> >  config AD7606_IFACE_PARALLEL
> >         tristate "Analog Devices AD7606 ADC driver with parallel interface support"
> > -       depends on HAS_IOMEM
> > +       depends on HAS_IOPORT
> 
> While this driver uses ins[bw](), this seems unrelated to legacy
> I/O space, as the driver maps a MMIO region.  Probably different
> accessors should be used instead.

You're right on first glance it looks like a misuse of the ins[bw]()
accessors. I do wonder how that even works, if PCI_IOBASE is 0 it would
result in readsw()/readsb() with presumably the correct address but no
idea how this interacts witth x86's special I/O instructions.

> 
> Note that this driver has no in-tree users. Same for the SPI variant,
> but at least that one has modern json-schema DT bindings ;-)

Can't find any mention in the MAINTAINERS file either.

> 
> >         select AD7606
> >         help
> >           Say yes here to build parallel interface support for Analog Devices:
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds