linux-kernel - Re: [PATCH RFC v7 1/6] dt-bindings: display: add Unisoc's drm master bindings

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Date:   Tue, 29 Sep 2020 15:47:12 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Kevin Tang <kevin3.tang@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime@...no.tech>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Orson Zhai <orsonzhai@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH RFC v7 1/6] dt-bindings: display: add Unisoc's drm master bindings

On Tue, 29 Sep 2020 at 14:35, Kevin Tang <kevin3.tang@...il.com> wrote:
>
> Hi Rob,
> Component framework include master and component, here is master subnode.
> It seems that everyone else does it, why not me?
>
> Your comments on v6:
> "We generally try to avoid this virtual node as it doesn't represent
> any h/w. Can't you bind the driver to the DPU directly?"
>
> I'm sorry, maybe is my careless, I still don't understand why and how to do it

Devicetree is used to describe hardware rather than virtual things
like "sprd,display-subsystem" which is not a real device.
That's what I understand for Rob's comments here.

Chunyan

>
> Rob Herring <robh+dt@...nel.org> 于2020年9月29日周二 上午12:28写道：
>
> >
> > On Mon, Sep 28, 2020 at 3:17 AM Maxime Ripard <maxime@...no.tech> wrote:
> > >
> > > Hi!
> > >
> > > On Mon, Sep 28, 2020 at 02:27:35PM +0800, Kevin Tang wrote:
> > > > From: Kevin Tang <kevin.tang@...soc.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
> > > >
> > > > RFC v7:
> > > >   - Fix DTC unit name warnings
> > > >   - Fix the problem of maintainers
> > > >
> > > > Cc: Orson Zhai <orsonzhai@...il.com>
> > > > Cc: Chunyan Zhang <zhang.lyra@...il.com>
> > > > Signed-off-by: Kevin Tang <kevin.tang@...soc.com>
> > > > ---
> > > >  .../display/sprd/sprd,display-subsystem.yaml       | 39 ++++++++++++++++++++++
> > > >  1 file changed, 39 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml b/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> > > > new file mode 100644
> > > > index 0000000..9487a39
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> > > > @@ -0,0 +1,39 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/display/sprd/sprd,display-subsystem.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Unisoc DRM master device
> > > > +
> > > > +maintainers:
> > > > +  - Kevin Tang <kevin.tang@...soc.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:
> > > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > > +    description:
> > > > +      Should contain a list of phandles pointing to display interface port
> > > > +      of DPU devices.
> > >
> > > Generally speaking, driver-specific properties should be prefixed by the
> > > vendor name to avoid any conflict with generic properties (like the
> > > OF-Graph ports subnode in this case)
> >
> > We try to avoid this virtual node altogether which I commented about
> > on v6 which was ignored.
> >
> > Rob