linux-kernel - Re: [PATCH] media: staging: tegra-vde: Disable building with COMPILE

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Date:   Thu, 29 Aug 2019 14:40:34 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     YueHaibing <yuehaibing@...wei.com>, digetx@...il.com,
        mchehab@...nel.org, gregkh@...uxfoundation.org,
        jonathanh@...dia.com, robin.murphy@....com,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH] media: staging: tegra-vde: Disable building with
 COMPILE_TEST

On Thu, Aug 29, 2019 at 01:39:32PM +0200, Hans Verkuil wrote:
> On 8/26/19 3:31 PM, YueHaibing wrote:
> > If COMPILE_TEST is y and IOMMU_SUPPORT is n, selecting TEGRA_VDE
> > to m will set IOMMU_IOVA to m, this fails the building of
> > TEGRA_HOST1X and DRM_TEGRA which is y like this:
> > 
> > drivers/gpu/host1x/cdma.o: In function `host1x_cdma_init':
> > cdma.c:(.text+0x66c): undefined reference to `alloc_iova'
> > cdma.c:(.text+0x698): undefined reference to `__free_iova'
> > 
> > drivers/gpu/drm/tegra/drm.o: In function `tegra_drm_unload':
> > drm.c:(.text+0xeb0): undefined reference to `put_iova_domain'
> > drm.c:(.text+0xeb4): undefined reference to `iova_cache_put'
> > 
> > Reported-by: Hulk Robot <hulkci@...wei.com>
> > Fixes: 6b2265975239 ("media: staging: tegra-vde: Fix build error")
> > Fixes: b301f8de1925 ("media: staging: media: tegra-vde: Add IOMMU support")
> > Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> > ---
> >  drivers/staging/media/tegra-vde/Kconfig | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/staging/media/tegra-vde/Kconfig b/drivers/staging/media/tegra-vde/Kconfig
> > index ba49ea5..a41d30c 100644
> > --- a/drivers/staging/media/tegra-vde/Kconfig
> > +++ b/drivers/staging/media/tegra-vde/Kconfig
> > @@ -1,9 +1,9 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >  config TEGRA_VDE
> >  	tristate "NVIDIA Tegra Video Decoder Engine driver"
> > -	depends on ARCH_TEGRA || COMPILE_TEST
> > +	depends on ARCH_TEGRA
> 
> What happens if you drop this change,
> 
> >  	select DMA_SHARED_BUFFER
> > -	select IOMMU_IOVA if (IOMMU_SUPPORT || COMPILE_TEST)
> > +	select IOMMU_IOVA if IOMMU_SUPPORT
> 
> but keep this change?
> 
> iova.h has stubs that are used if IOMMU_IOVA is not set, so it should
> work when compile testing this tegra-vde driver.
> 
> Haven't tried it, but making sure that compile testing keep working is
> really important.

Yeah, that variant seems to work for me. I think it's also more correct
because the IOMMU_IOVA if IOMMU_SUPPORT dependency really says that the
IOVA usage is bound to IOMMU support. If IOMMU support is not enabled,
then IOVA is not needed either, so the dummies will do just fine.

Thierry

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