linux-kernel - Test of [PATCH 1/1] staging: pi433: fix problem with division in rf69_set

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Date:   Thu, 20 Jul 2017 17:57:30 +0200 (CEST)
From:   Marcus Wolf <marcus.wolf@...f-entwicklungen.de>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "kbuild-all@...org" <kbuild-all@...org>,
        Greg KH <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        driverdevel <devel@...verdev.osuosl.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Grant Likely <grant.likely@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Test of [PATCH 1/1] staging: pi433: fix problem with division in
 rf69_set_deviation

Hi!

Since I don't have an environment for m68k and I would appreciate not
having to set it up, I would be very happy, if someone could give
the patch, named in the subjext, a try on ARCH=m68k...

Thanks,

Marcus



> Geert Uytterhoeven <geert@...ux-m68k.org> hat am 20. Juli 2017 um 14:27
> geschrieben:
>
>
> Hi Dan,
>
> On Thu, Jul 20, 2017 at 1:37 PM, Dan Carpenter <dan.carpenter@...cle.com>
> wrote:
> > On Thu, Jul 20, 2017 at 01:23:05PM +0200, Marcus Wolf wrote:
> >> below you can see the report with the error on m68k. It was sent to me from
> >> a
> >> test robot of intel.
> >>
> >> According to my research, this problem occured, because there is no
> >> hardware
> >> support for floating point on the m68k (or it was configured not to use
> >> it).
> >> Therefore gcc uses an internal function, provided by libgcc. Obviously
> >> libgcc
> >> wasn't linked...
> >>
> >> I don't know how to come arround this problem by modifying my code (except
> >> reducing the accuracy of the calculation by not using floating point).
> >
> > I don't see any floating point? You're not allowed to use floating
> > point in the kernel.
>
> Indeed. __udivdi3 is used for 64-bit by 32-bit division.
>
> >> Can we ignore the error or can I do something else?
> >> Maybe a special include just in case of m68k can help??!?
> >> I don't have an environment for building m68k.
>
> https://www.kernel.org/pub/tools/crosstool/
>
> > I think the answer is to use div_u64() and div64_u64 instead of
> > do_div()?
>
> do_div() is fine
> The link error is not caused by do_div(), but by not using do_div() where
> needed.
>
> > Or you could just add a depend in the Kconfig.
>
> Depend on what? !M68K? It's gonna fail on several 32-bit platforms.
> 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
>