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

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Message-Id: <11fdef9b-413d-4f88-b3d3-e5b27a88cf6f@app.fastmail.com>
Date: Fri, 05 Apr 2024 13:24:28 +0200
From: "Arnd Bergmann" <arnd@...nel.org>
To: "Geert Uytterhoeven" <geert@...ux-m68k.org>
Cc: "Michael Schmitz" <schmitzmic@...il.com>,
 "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 12:16, Geert Uytterhoeven wrote:
> 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:
>>
>> For the Q40, it may be better in the long run to change the
>> drivers to just use MMIO directly though.
>
> Q40 uses ISA.

Ah, indeed. I got confused by  the NE2000 example as that
contains "depends on (ISA || (Q40 && m)", which would have
indicated that it's not actually using CONFIG_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...

It's definitely still better to use an abstraction layer for MMIO
accesses using inline asm instructions than open-coding the
volatile pointer dereferences. Over time we have gotten better
at defining which of the available abstractions should be used
for a given bus, so inb()/outb() is now only really used for
things derived from ISA in some form, including e.g. PCI and LPC.

> 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...
>
> arch/m68k/include/asm/floppy.h on Sun-3x might be the only offender?

Could be. I think we can leave this one to whoever tries to get
sun3x floppy support working, it's been marked broken for a while
(see below). If there are any others, they will cause pretty
obvious build failures once inb()/outb() are removed from the
build, and they should be trivial to fix then.

     Arnd

commit f1e0f28a85001f4faa3ea930fcf201933f42340e
Author: akpm <akpm>
Date:   Mon Jan 19 18:31:30 2004 +0000

    [PATCH] M68k floppy selection
    
    From: Geert Uytterhoeven <geert@...ux-m68k.org>
    
    Floppy: On m68k, PC-style floppies are used on Q40/Q60 and Sun-3x only. Sun-3x
    floppy is currently broken (needs I/O abstractions)
    
    BKrev: 400c2282G1O-TsH5FiwzPbOorftQhg

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 2dce1d2699a9..32fdec34568e 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -6,7 +6,7 @@ menu "Block devices"
 
 config BLK_DEV_FD
        tristate "Normal floppy disk support"
-       depends on !X86_PC9800 && !ARCH_S390
+       depends on (!X86_PC9800 && !ARCH_S390 && !M68K) || Q40 || (SUN3X && BROKEN)
        ---help---
          If you want to use the floppy disk drive(s) of your PC under Linux,
          say Y. Information about this driver, especially important for IBM