linux-kernel - Re: build failure of next-20220906 due to 396369d67549 ("drm: vkms: Add support to the RGB565 format")

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Date:   Wed, 7 Sep 2022 07:50:44 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Igor Matheus Andrade Torrente <igormtorrente@...il.com>
Cc:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Melissa Wen <melissa.srw@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-next <linux-next@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Haneen Mohammed <hamohammed.sa@...il.com>
Subject: Re: build failure of next-20220906 due to 396369d67549 ("drm: vkms:
 Add support to the RGB565 format")

On Wed, Sep 07, 2022 at 07:47:32AM +0200, Daniel Vetter wrote:
> On Tue, Sep 06, 2022 at 08:35:49PM -0300, Igor Matheus Andrade Torrente wrote:
> > On 9/6/22 18:26, Sudip Mukherjee wrote:
> > > On Tue, Sep 6, 2022 at 4:59 PM Sudip Mukherjee (Codethink)
> > > <sudipm.mukherjee@...il.com> wrote:
> > > > 
> > > > Hi All,
> > > > 
> > > > The builds of next-20220906 fails for mips, xtensa and arm allmodconfig.
> > > > 
> > > > The errors in mips and xtensa are:
> > > > 
> > > > ERROR: modpost: "__divdi3" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > > > ERROR: modpost: "__udivdi3" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > > > 
> > > > The error in arm is:
> > > > 
> > > > ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > > > ERROR: modpost: "__aeabi_ldivmod" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > > > 
> > > > 
> > > > Trying to do a git bisect to find out the offending commit.
> > > 
> > > git bisect points to 396369d67549 ("drm: vkms: Add support to the
> > > RGB565 format")
> > 
> > Are these architectures incapable of doing 64bits int division?
> 
> Yeah 32bit archs in general can't do that, and you have to use the right
> macros because otherwise gcc falls back to its own built-ins, and those
> don't exist in the kernel since the kernel isn't (cannot!) linked against
> any userspace library.
> 
> For pretty much this reasons it's really good to build test against 32bit
> x86, or probably more relevant these days, 32bit arm.

Forgot to add: include/math.h for all your division needs.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch