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

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Message-ID: <CAPBb6MXujfdLaMhcW4vj2U_Ev-H74Fu-a6D1HEyhyrQ3huV8vw@mail.gmail.com>
Date:   Mon, 5 Oct 2020 20:29:40 +0900
From:   Alexandre Courbot <acourbot@...omium.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        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

On Mon, Oct 5, 2020 at 5:49 PM Sakari Ailus
<sakari.ailus@...ux.intel.com> wrote:
>
> Hi Alexandre,
>
> On Sun, Oct 04, 2020 at 09:22:34PM +0900, 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
>
> Thanks for the patch!
>
> Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>

Thanks!

>
> I wonder if this driver suffers from similar object lifetime management
> issues than V4L2 and MC do, albeit not related to either. Say, what happens
> if you unbind the other device while mtk-vcodec is in use?

That's a question that maybe the driver maintainers can answer, but
from my experience during development I have been able to unload one
of the two mtk-vcodec-* modules while keeping the other one active.