linux-kernel - Re: [PATCH] [RESEND] gpu: ipu-v3: add DRM dependency

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Message-ID: <CAK8P3a1AS9hRvCiZcshLsYTN_jFLcbkyNJqqiPLiTFqdU11xaQ@mail.gmail.com>
Date:   Tue, 25 Jul 2017 09:33:06 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RESEND] gpu: ipu-v3: add DRM dependency

On Mon, Jul 24, 2017 at 10:05 AM, Philipp Zabel <p.zabel@...gutronix.de> wrote:
> On Fri, 2017-07-21 at 22:56 +0200, Arnd Bergmann wrote:
>> The new PRE/PRG driver code causes a link failure when DRM is disabled:
>>
>> drivers/gpu/ipu-v3/ipu-pre.o: In function `ipu_pre_configure':
>> ipu-pre.c:(.text.ipu_pre_configure+0x18): undefined reference to `drm_format_info'
>> drivers/gpu/ipu-v3/ipu-prg.o: In function ` ':
>> ipu-prg.c:(.text.ipu_prg_format_supported+0x8): undefined reference to `drm_format_info'
>>
>> Adding a Kconfig dependency on DRM means we don't run into this problem
>> any more. This might not be the best solution though, as the ipu seems
>> to have been intentionally kept separate from DRM in the past.
>>
>> Fixes: ea9c260514c1 ("gpu: ipu-v3: add driver for Prefetch Resolve Gasket")
>> Link: https://patchwork.kernel.org/patch/9636665/
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> ---
>> Originally sent on March 21, but got no reply for it. Resending unchanged
>> as it is still needed in v4.13-rc1
>
> thank you for fix and for the resend. I have the original patch in my
> inbox, I'm sorry I overlooked it.
>
> I would still like to keep the ipu-v3 driver buildable without DRM
> enabled. For now, I have applied your patch as is.

Ok, thanks!

I'm pretty sure we can find a way to solve it so that you don't depend
on DRM, but we should discuss what that would look like.

Are you mainly interested in being able to build-test without DRM,
or do you actually want the ipu_pre_configure() and
ipu_prg_format_supported() functions to work correctly in that case?

If you only need build-testing, you could have a simple wrapper like

const struct drm_format_info *ipu_format_info(u32 format)
{
         static const struct drm_format_info invalid = {};

         if (!IS_REACHABLE(CONFIG_DRM))
                  return &invalid;

         return drm_format_info(format);
}

The more useful way to solve it would be more work, we could for
instance move (parts of) drivers/gpu/drm/drm_fourcc.c into
lib/fourcc.c and have it built whenever at least DRM or IPU_v3
are enabled.

         Arnd