linux-kernel - Re: [PATCH 0/1] m68k: Handle HAS

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Date: Mon, 8 Apr 2024 10:19:50 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Michael Schmitz <schmitzmic@...il.com>
Cc: Arnd Bergmann <arnd@...nel.org>, Niklas Schnelle <schnelle@...ux.ibm.com>, 
	linux-m68k@...ts.linux-m68k.org, Heiko Carstens <hca@...ux.ibm.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] m68k: Handle HAS_IOPORT dependencies

On Fri, Apr 5, 2024 at 8:36 PM Michael Schmitz <schmitzmic@...il.com> wrote:
> Am 05.04.2024 um 23:16 schrieb Geert Uytterhoeven:
> > On Wed, Apr 3, 2024 at 8:35 PM Arnd Bergmann <arnd@...nel.org> wrote:
> >> On Wed, Apr 3, 2024, at 20:11, Michael Schmitz wrote:
> >>> how do you propose we handle legacy drivers that do depend on
> >>> inb()/outb() functions (_not_ actual ISA I/O) on architectures that map
> >>> inb()/outb() to MMIO functions?
> >>>
> >>> (In my case, that's at least ne.c - Geert ought to have a better
> >>> overview what else does use inb()/outb() on m68k)
> >>
> >> If a machine provides an inb()/outb() set of operations that
> >> is actually used, it should set HAS_IOPORT.
> >>
> >> For the Q40, it may be better in the long run to change the
> >> drivers to just use MMIO directly though.
> >
> > Q40 uses ISA.
> >
> > Michael is worried about non-ISA drivers using inb() and friends.
> > At some point in time (i.e. eons ago), we were told it was better to
> > use in[bwl]()/read[bwl]() instead of directly dereferencing volatile
> > pointers...
> >
> > Anyway, I don't think we have many users of inb() and friends left, and
> > I assume the bots should have detected any/most remaining users in Niklas'
> > branch...
>
> All the 8390 based ethernet drivers still use inb() and friends.
>
> That is the main reason for the terrible hacks in
> arch/m68k/include/asm/io_mm.h ...
>
> The last time I tried to add support for a different PCMCIA ethernet
> adapter to apne.c _without_ adding to the hacks in io_mm.h, I wasn't
> getting anywhere with the netdev crowd. That was ages ago, and I doubt
> their enthusiasm for a rewrite of the 8390 code base to avoid using
> inb() on MMIO architectures will be any better now.

As Arnd already discovered later in this thread, AMIGA_PCMCIA
(sort of) selects ISA, so APNE can be considered a "real" ISA. driver,
so it can keep on using inb() and friends.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

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