Re: [PATCH 0/3] drm/amdgpu: enable DKMS build

From: Thierry Reding <thierry.reding@gmail.com>
To: "Christian König" <deathsimple@vodafone.de>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 0/3] drm/amdgpu: enable DKMS build
Date: Tue, 24 Nov 2015 11:33:18 +0100	[thread overview]
Message-ID: <20151124103318.GE6149@ulmo> (raw)
In-Reply-To: <56543707.9090909@vodafone.de>

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On Tue, Nov 24, 2015 at 11:08:07AM +0100, Christian König wrote:
> On 24.11.2015 10:36, Thierry Reding wrote:
> >On Tue, Nov 24, 2015 at 09:59:09AM +0100, Daniel Vetter wrote:
> >>On Tue, Nov 24, 2015 at 04:55:19PM +0800, Jammy Zhou wrote:
> >>>This series enable the DKMS build of amdgpu driver.
> >>For the curious: What's DKMS?
> >I believe in this context it's "Dynamic Kernel Module Support":
> >
> >	https://wiki.debian.org/KernelDKMS
> 
> Yeah, correct.
> 
> >
> >I'm somewhat surprised that one would have to do something special to
> >the kernel build system to "enable" such a build. But perhaps this is
> >completely unrelated.
> 
> I'm a bit torn apart on this. On the one hand I'm not sure if we have
> drivers upstream explicitly supporting this as well?

It's been a long time since I last used Debian and worked with DKMS, but
wasn't the original idea for DKMS to be used on out-of-tree modules? Why
the need to build in-tree modules with DKMS? Shouldn't that be done as
part of a regular linux-image/linux-modules build?

> On the other hand it's just the Makefiles which need to be written in a way
> which makes them relocatable. E.g. no absolute path like
> drivers/gpu/drm/amd/... in them and that's a good idea anyway.

To clarify, I'm not opposing the change, I just thought it weird that
the kernel build had to be modified to support an external build system.
But in general it seems to be rare that drivers even need to specific
additional ccflags, which would explain my surprise.

There's precedent for using $(src), see drivers/gpu/drm/Makefile, so I
don't see any reason why this would be objectionable.

> Maybe just changing the commit message to "don't use absolute paths in the
> makefiles" would be sufficient?

I don't mind the mention of DKMS either, but perhaps extending the
commit message with a few words about what DKMS is and why the change
needs to happen (i.e. $(src) used for relocation) would be a good idea
anyway.

Thierry

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