linux-kernel - Re: [PATCH] parport_pc: Also enable driver for PCI systems

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Date:   Mon, 14 Feb 2022 09:20:49 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
        linux-kernel@...r.kernel.org,
        Niklas Schnelle <schnelle@...ux.ibm.com>
Subject: Re: [PATCH] parport_pc: Also enable driver for PCI systems

Hi Maciej,

CC Niklas

On Sun, Feb 13, 2022 at 1:45 PM Maciej W. Rozycki <macro@...am.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@...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