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

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Message-ID: <d9bdfa48-572a-caa1-229b-44565690d9e6@gmail.com>
Date: Sat, 6 Apr 2024 07:36:26 +1300
From: Michael Schmitz <schmitzmic@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>, Arnd Bergmann <arnd@...nel.org>
Cc: 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

Hi Geert,

Am 05.04.2024 um 23:16 schrieb Geert Uytterhoeven:
> Hi Arnd,
>
> 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.

Just saying ...

	Michael

>
> arch/m68k/include/asm/floppy.h on Sun-3x might be the only offender?
>
> Gr{oetje,eeting}s,
>
>                         Geert
>