linux-kernel - Re: [PATCH v3 2/2] media: mtk-vcodec: fix build breakage when one of VPU or SCP is enabled

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Date:   Mon, 12 Oct 2020 09:43:07 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Alexandre Courbot <acourbot@...omium.org>
Cc:     Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, gnurou@...il.com,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v3 2/2] media: mtk-vcodec: fix build breakage when one
 of VPU or SCP is enabled

Em Mon, 12 Oct 2020 14:35:57 +0900
Alexandre Courbot <acourbot@...omium.org> escreveu:

> 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
> Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> ---
>  drivers/media/platform/Kconfig                | 22 +++++++++++++++----
>  drivers/media/platform/mtk-vcodec/Makefile    | 10 +++++++--
>  .../platform/mtk-vcodec/mtk_vcodec_fw_priv.h  | 18 +++++++++++++++
>  3 files changed, 44 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
> index a3cb104956d5..457b6c39ddc0 100644
> --- a/drivers/media/platform/Kconfig
> +++ b/drivers/media/platform/Kconfig
> @@ -253,18 +253,32 @@ 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
> +	# The two following lines ensure we have the same state ("m" or "y") as
> +	# our dependencies, to avoid missing symbols during link.
> +	depends on VIDEO_MEDIATEK_VPU || !VIDEO_MEDIATEK_VPU
> +	depends on MTK_SCP || !MTK_SCP
>  	select VIDEOBUF2_DMA_CONTIG
>  	select V4L2_MEM2MEM_DEV
> -	select VIDEO_MEDIATEK_VPU
> -	select MTK_SCP
> +	select VIDEO_MEDIATEK_VCODEC_VPU if VIDEO_MEDIATEK_VPU
> +	select VIDEO_MEDIATEK_VCODEC_SCP if MTK_SCP
>  	help
>  	    Mediatek video codec driver provides HW capability to
> -	    encode and decode in a range of video formats
> -	    This driver rely on VPU driver to communicate with VPU.
> +	    encode and decode in a range of video formats on MT8173
> +	    and MT8183.
> +
> +	    Note that support for MT8173 requires VIDEO_MEDIATEK_VPU to
> +	    also be selected. Support for MT8183 depends on MTK_SCP.
>  
>  	    To compile this driver as modules, choose M here: the
>  	    modules will be called mtk-vcodec-dec and mtk-vcodec-enc.

Just my 2 cents here, and to complement my last e-mail, the helper message
here IMO is a lot more confusing than if you do this, instead:

	config VIDEO_MEDIATEK_CODEC
	         depends on VIDEO_MEDIATEK_VPU_SCP || VIDEO_MEDIATEK_VPU
		 default y

	config VIDEO_MEDIATEK_VPU
            depends on VIDEO_DEV && VIDEO_V4L2
            depends on ARCH_MEDIATEK || COMPILE_TEST
            tristate "Enable Mediatek Video Processor Unit for MT8173"
	    help
		Select this option to enable Mediatek VPU on MT8173.

	config VIDEO_MEDIATEK_VPU_SCP
            depends on VIDEO_DEV && VIDEO_V4L2
            depends on ARCH_MEDIATEK || COMPILE_TEST
            tristate "Enable Mediatek Video Processor Unit for MT8183"
	    help
		Select this option to enable Mediatek VPU on MT8183.

To be clear, from my side, I can live with either one of the alternatives,
but, IMHO, the above is a lot clearer for anyone wanting to use
VPU, as, if MTK_SCP is disabled, the MT8183 Kconfig prompt will
disappear.


Thanks,
Mauro