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From:   Rob Herring <robh+dt@kernel.org>
Date:   Thu, 27 Feb 2020 10:50:08 -0600
Message-ID: <CAL_JsqL08g0TaNob7gcKgTx5OXgwBEfKy6f5AK73xuYhMRMNkw@mail.gmail.com>
Subject: Re: [PATCH RFC v4 1/6] dt-bindings: display: add Unisoc's drm master bindings
To:     Kevin Tang <kevin3.tang@gmail.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Mark Rutland <mark.rutland@arm.com>,
        Orson Zhai <orsonzhai@gmail.com>,
        Baolin Wang <baolin.wang@linaro.org>,
        Lyra Zhang <zhang.lyra@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>
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On Wed, Feb 26, 2020 at 3:46 AM Kevin Tang <kevin3.tang@gmail.com> wrote:
>
> From: Kevin Tang <kevin.tang@unisoc.com>
>
> The Unisoc DRM master device is a virtual device needed to list all
> DPU devices or other display interface nodes that comprise the
> graphics subsystem
>
> Cc: Orson Zhai <orsonzhai@gmail.com>
> Cc: Baolin Wang <baolin.wang@linaro.org>
> Cc: Chunyan Zhang <zhang.lyra@gmail.com>
> Signed-off-by: Kevin Tang <kevin.tang@unisoc.com>
> ---
>  .../devicetree/bindings/display/sprd/drm.yaml      | 36 ++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/sprd/drm.yaml
>
> diff --git a/Documentation/devicetree/bindings/display/sprd/drm.yaml b/Documentation/devicetree/bindings/display/sprd/drm.yaml
> new file mode 100644
> index 0000000..b5792c0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/sprd/drm.yaml
> @@ -0,0 +1,36 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/sprd/drm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Unisoc DRM master device
> +
> +maintainers:
> +  - Mark Rutland <mark.rutland@arm.com>
> +
> +description: |
> +  The Unisoc DRM master device is a virtual device needed to list all
> +  DPU devices or other display interface nodes that comprise the
> +  graphics subsystem.
> +
> +properties:
> +  compatible:
> +    const: sprd,display-subsystem
> +
> +  ports:
> +    description:
> +      Should contain a list of phandles pointing to display interface port
> +      of DPU devices.
> +
> +required:
> +  - compatible
> +  - ports
> +
> +examples:
> +  - |
> +    display-subsystem {
> +        compatible = "sprd,display-subsystem";
> +        ports = <&dpu_out>;

We try to avoid these virtual nodes and bind with actual h/w nodes.
Can you have more than one DPU and if so does it need to be a single
DRM driver instance?

Rob