linux-kernel - Re: [PATCH 1/2] video: fbdev: amifb: remove dead APUS support

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Date:   Tue, 2 Jun 2020 13:07:33 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 1/2] video: fbdev: amifb: remove dead APUS support

Hi!

On 6/2/20 1:04 PM, Geert Uytterhoeven wrote:
>> What do you mean with the sentence "when arch/ppc/ was still king"?
> 
> Ah, Bartl copied that from my email ;-)
> 
> There used to be APUS support under arch/ppc/.
> Later, 32-bit arch/ppc/ and 64-bit arch/ppc64/ were merged in a new\
> architecture port under arch/powerpc/, and the old ones were dropped.
> APUS was never converted, and thus dropped.

Ah, yes. Similar to the merge with x86.

>> Does that mean - in the case we would re-add APUS support in the future, that
>> these particular changes would not be necessary?
> 
> They would still be necessary, as PowerPC doesn't grok m68k instructions.
> Alternatively, we could just drop the m68k inline asm, and retain the C
> version instead?  I have no idea how big of a difference that would make
> on m68k, using a more modern compiler than when the code was written
> originally.

Hmm, no idea. I would keep the assembly for the time being. This was just
a question out of curiosity. We could still consider such a change if
someone should consider working on APUS support again.

> Note that all of this is used only for cursor handling, which I doubt is
> actually used by any user space application. The only exception is the
> DIVUL() macro, which is used once during initialization, thus also not
> performance critical.
I see, thanks.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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