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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 14 Feb 2022 09:20:49 +0100
Message-ID: <CAMuHMdW-utcFzCZTgqONjxs=U662nF0=aBQu7Zi7FBQouwiA3g@mail.gmail.com>
Subject: Re: [PATCH] parport_pc: Also enable driver for PCI systems
To:     "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc:     Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Jeff Dike <jdike@addtoit.com>,
        Richard Weinberger <richard@nod.at>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org,
        linux-kernel@vger.kernel.org,
        Niklas Schnelle <schnelle@linux.ibm.com>
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Hi Maciej,

CC Niklas

On Sun, Feb 13, 2022 at 1:45 PM Maciej W. Rozycki <macro@orcam.me.uk> wrote:
> Nowadays PC-style parallel ports come in the form of PCI and PCIe option
> cards and there are some combined parallel/serial option cards as well
> that we handle in the parport subsystem.  There is nothing in particular
> that would prevent them from being used in any system equipped with PCI
> or PCIe connectivity, except that we do not permit the PARPORT_PC config
> option to be selected for platforms for which ARCH_MIGHT_HAVE_PC_PARPORT
> has not been set for.
>
> The only PCI platforms that actually can't make use of PC-style parallel
> port hardware are those newer PCIe systems that have no support for I/O
> cycles in the host bridge, required by such parallel ports.  An example
> of such a host bridge is the POWER9 PHB4 device, but it is an exception
> rather than the norm.  Also it is not clear whether the serial port side

Note that this hardware dependency is being addressed in
"[RFC 00/32] Kconfig: Introduce HAS_IOPORT and LEGACY_PCI options"
https://lore.kernel.org/all/20211227164317.4146918-1-schnelle@linux.ibm.com/

> --- linux-macro.orig/drivers/parport/Kconfig
> +++ linux-macro/drivers/parport/Kconfig
> @@ -42,7 +42,7 @@ if PARPORT
>
>  config PARPORT_PC
>         tristate "PC-style hardware"
> -       depends on ARCH_MIGHT_HAVE_PC_PARPORT
> +       depends on ARCH_MIGHT_HAVE_PC_PARPORT || PCI
>         help
>           You should say Y here if you have a PC-style parallel port. All
>           IBM PC compatible computers and some Alphas have PC-style
> @@ -77,7 +77,7 @@ config PARPORT_PC_FIFO
>
>  config PARPORT_PC_SUPERIO
>         bool "SuperIO chipset support"
> -       depends on PARPORT_PC && !PARISC
> +       depends on ARCH_MIGHT_HAVE_PC_PARPORT && PARPORT_PC && !PARISC
>         help
>           Saying Y here enables some probes for Super-IO chipsets in order to
>           find out things like base addresses, IRQ lines and DMA channels.  It
>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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