linux-kernel - Re: [PATCH v3 02/16] dt-bindings: media: mtk-vcodec: document SCP node

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Date:   Wed, 22 Jul 2020 18:37:43 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Alexandre Courbot <acourbot@...omium.org>
Cc:     Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Yunfei Dong <yunfei.dong@...iatek.com>,
        Maoguang Meng <maoguang.meng@...iatek.com>,
        linux-media <linux-media@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 02/16] dt-bindings: media: mtk-vcodec: document SCP node

On Mon, 13 Jul 2020 at 03:09, Alexandre Courbot <acourbot@...omium.org> wrote:
>
> The mediatek codecs can use either the VPU or the SCP as their interface
> to firmware. Reflect this in the DT bindings.
>
> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
> Acked-by: Tiffany Lin <tiffany.lin@...iatek.com>
> ---
>  Documentation/devicetree/bindings/media/mediatek-vcodec.txt | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/media/mediatek-vcodec.txt b/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> index b6b5dde6abd8..7aef0a4fe207 100644
> --- a/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> +++ b/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> @@ -19,7 +19,9 @@ Required properties:
>  - iommus : should point to the respective IOMMU block with master port as
>    argument, see Documentation/devicetree/bindings/iommu/mediatek,iommu.txt
>    for details.
> -- mediatek,vpu : the node of video processor unit
> +One of the two following nodes:
> +- mediatek,vpu : the node of the video processor unit, if using VPU.
> +- mediatek,scp : the noode of the SCP unit, if using SCP.
>

This interface doesn't enforce the fact only one of the two
should be present, but not both (which is the case, right?).

I hope I'm not bikeshedding here, but from an interface POV,
would it be cleaner to just have a single mediatek,coprocessor
property, and then use of_device_is_compatible
to distinguish VPU from SCP type?

Moreover, I'd argue you don't need a dt-binding change
and should just keep the current mediatek-vpu property,
and then rely on of_device_is_compatible.

Regards,
Ezequiel

>
>  Example:
> --
> 2.27.0.383.g050319c2ae-goog
>