linux-kernel - Re: [PATCH v2] media: mtk-vcodec: fix builds when remoteproc is disabled

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Date:   Thu, 8 Oct 2020 23:02:08 +0900
From:   Alexandre Courbot <acourbot@...omium.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v2] media: mtk-vcodec: fix builds when remoteproc is disabled

Hi Hans, thanks for taking the time to look at this!

On Thu, Oct 8, 2020 at 10:12 PM Hans Verkuil <hverkuil-cisco@...all.nl> wrote:
>
> On 08/10/2020 15:07, Hans Verkuil wrote:
> > Hi Alexandre,
> >
> > On 04/10/2020 14:22, Alexandre Courbot wrote:
> >> The addition of MT8183 support added a dependency on the SCP remoteproc
> >> module. However the initial patch used the "select" Kconfig directive,
> >> which may result in the SCP module to not be compiled if remoteproc was
> >> disabled. In such a case, mtk-vcodec would try to link against
> >> non-existent SCP symbols. "select" was clearly misused here as explained
> >> in kconfig-language.txt.
> >>
> >> Replace this by a "depends" directive on at least one of the VPU and
> >> SCP modules, to allow the driver to be compiled as long as one of these
> >> is enabled, and adapt the code to support this new scenario.
> >>
> >> Also adapt the Kconfig text to explain the extra requirements for MT8173
> >> and MT8183.
> >>
> >> Reported-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> >> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
> >> Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested
> >> ---
> >>  drivers/media/platform/Kconfig                | 10 +--
> >>  .../media/platform/mtk-vcodec/mtk_vcodec_fw.c | 72 ++++++++++++-------
> >>  2 files changed, 54 insertions(+), 28 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
> >> index a3cb104956d5..98eb62e49ec2 100644
> >> --- a/drivers/media/platform/Kconfig
> >> +++ b/drivers/media/platform/Kconfig
> >> @@ -253,14 +253,16 @@ config VIDEO_MEDIATEK_VCODEC
> >>      depends on MTK_IOMMU || COMPILE_TEST
> >>      depends on VIDEO_DEV && VIDEO_V4L2
> >>      depends on ARCH_MEDIATEK || COMPILE_TEST
> >> +    depends on VIDEO_MEDIATEK_VPU || MTK_SCP
> >
> > Close, but no cigar.
> >
> > If VIDEO_MEDIATEK_VPU=y and MTK_SCP=m, then VIDEO_MEDIATEK_VCODEC can be configured
> > to y, and then it won't be able to find the scp_ functions.
> >
> > To be honest, I'm not sure how to solve this.
>
> Found it. Add this:
>
>         depends on MTK_SCP || !MTK_SCP
>         depends on VIDEO_MEDIATEK_VPU || !VIDEO_MEDIATEK_VPU
>
> Ugly as hell, but it appears to be the correct incantation for this.

But doesn't it mean that the driver can be compiled if !MTK_SCP and
!VIDEO_MEDIATEK_VPU? That's the one case we want to avoid.