linux-kernel - Re: [PATCH RESEND 1/4] dt-bindings: drm/bridge: analogix-anx7688: Add ANX7688 transmitter binding

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Message-ID: <CAJMQK-j1GPxipMkba1VO3xCEOiLJi4ibotKFeRSGZ0e6nOG3Ng@mail.gmail.com>
Date:   Fri, 20 Dec 2019 11:51:09 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Rob Herring <robh@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH RESEND 1/4] dt-bindings: drm/bridge: analogix-anx7688: Add
 ANX7688 transmitter binding

On Fri, Dec 20, 2019 at 11:22 AM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Hsin-Yi,
>
> On Fri, Dec 20, 2019 at 11:20:13AM +0800, Hsin-Yi Wang wrote:
> > On Fri, Dec 20, 2019 at 4:45 AM Rob Herring wrote:
> > > On Wed, Dec 11, 2019 at 02:19:08PM +0800, Hsin-Yi Wang wrote:
> > > > From: Nicolas Boichat <drinkcat@...omium.org>
> > > >
> > > > Add support for analogix,anx7688
> > > >
> > > > Signed-off-by: Nicolas Boichat <drinkcat@...omium.org>
> > > > Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> > > > ---
> > > > Change from RFC to v1:
> > > > - txt to yaml
> > > > ---
> > > >  .../bindings/display/bridge/anx7688.yaml      | 60 +++++++++++++++++++
> > > >  1 file changed, 60 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/display/bridge/anx7688.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/anx7688.yaml b/Documentation/devicetree/bindings/display/bridge/anx7688.yaml
> > > > new file mode 100644
> > > > index 000000000000..cf79f7cf8fdf
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/anx7688.yaml
> > > > @@ -0,0 +1,60 @@
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/display/bridge/anx7688.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Analogix ANX7688 SlimPort (Single-Chip Transmitter for DP over USB-C)
> > > > +
> > > > +maintainers:
> > > > +  - Nicolas Boichat <drinkcat@...omium.org>
> > > > +
> > > > +description: |
> > > > +  The ANX7688 is a single-chip mobile transmitter to support 4K 60 frames per
> > > > +  second (4096x2160p60) or FHD 120 frames per second (1920x1080p120) video
> > > > +  resolution from a smartphone or tablet with full function USB-C.
> > > > +
> > > > +  This binding only describes the HDMI to DP display bridge.
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: analogix,anx7688
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +    description: I2C address of the device
> > > > +
> > > > +  ports:
> > > > +    type: object
> > > > +
> > > > +    properties:
> > > > +      port@0:
> > > > +        type: object
> > > > +        description: |
> > > > +          Video port for HDMI input
> > > > +
> > > > +      port@1:
> > > > +        type: object
> > > > +        description: |
> > > > +          Video port for eDP output
> > > > +
> > > > +    required:
> > > > +      - port@0
> > >
> > > Sometimes you have no output?
> >
> > Yes, only input is required.
>
> But what happens in that case ? What's the use of a bridge with a
> non-connected output ? :-)
>
There's output connected, but doesn't need a driver. For example, in
our use case it's connected to a usb-c connector. We don't need to
state it in dts.
I also checked https://elixir.bootlin.com/linux/v5.5-rc2/source/Documentation/devicetree/bindings/display/bridge/anx6345.yaml
and thought that output could be optional. Also
https://elixir.bootlin.com/linux/v5.5-rc2/source/arch/arm64/boot/dts/allwinner/sun50i-a64-teres-i.dts#L116
Or maybe we can add output in example as anx6345?
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - ports
> > >
> > > The example will have errors because it is missing 'ports'. Run 'make
> > > dt_binding_check'.
> > >
> > > Add:
> > >
> > > additionalProperties: false
> > >
> >
> > Ack, will fix this. Thanks
> >
> > > > +
> > > > +examples:
> > > > +  - |
> > > > +    anx7688: anx7688@2c {
> > > > +      compatible = "analogix,anx7688";
> > > > +      reg = <0x2c>;
> > > > +
> > > > +      port {
> > > > +        anx7688_in: endpoint {
> > > > +          remote-endpoint = <&hdmi0_out>;
> > > > +        };
> > > > +      };
> > > > +    };
>
> --
> Regards,
>
> Laurent Pinchart