linux-kernel - Re: [PATCH] m68k: math-emu: Fix dependencies of math emulation support

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Date:   Wed, 11 May 2022 14:02:01 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andreas Schwab <schwab@...ux-m68k.org>
Cc:     Greg Ungerer <gerg@...inux.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] m68k: math-emu: Fix dependencies of math emulation support

Hi Andreas,

On Wed, May 11, 2022 at 1:43 PM Andreas Schwab <schwab@...ux-m68k.org> wrote:
> On Mai 11 2022, Geert Uytterhoeven wrote:
> > Drop the dependency on MMU, as the code should work fine on 68020 and up
> > without MMU (which are not yet supported by Linux, though).
> > Add dependencies on M68K_CLASSIC (to rule out Coldfire) and FPU (to rule
> > out 68xxx below 68020).
>
> Depending on FPU looks strange, since that is supposed to be an FPU
> emulation, for CPUs that _lack_ an FPU (ie. 680[23]0 without the
> 6888[12], or 68LC0[46]0).

I picked FPU because it is selected by all of M680[2346]0.
Upon closer look, both the hard FPU and soft FPU code are protected
by CONFIG_FPU, so the latter looks like the right symbol.
The FPU emu code also relies on the CPU trapping on the proper
instructions, which I believe you need a 68020+ for, too?

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