Re: [PATCH/RFC 07/15] dt-bindings: display: renesas: lvds: Add renesas,companion property

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Geert,

On Mon, Mar 18, 2019 at 11:21:15AM +0100, Geert Uytterhoeven wrote:
> On Thu, Mar 7, 2019 at 12:24 AM Laurent Pinchart wrote:
> > Add a new optional renesas,companion property to point to the companion
> > LVDS encoder. This is used to support dual-link operation where the main
> > LVDS encoder splits even-numbered and odd-numbered pixels between the
> > two LVDS encoders.
> 
> Note that Documentation/devicetree/bindings/usb/generic.txt already
> describes a "companion" property without vendor prefix.
> 
> > The new property doesn't control the mode of operation, it only
> > describes the relationship between the master and companion LVDS
> > encoders.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> >  .../devicetree/bindings/display/bridge/renesas,lvds.txt     | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > index 900a884ad9f5..a720dbb5de69 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > @@ -45,6 +45,12 @@ OF graph bindings specified in Documentation/devicetree/bindings/graph.txt.
> >
> >  Each port shall have a single endpoint.
> >
> > +Optional properties:
> > +
> > +- renesas,companion : phandle to the companion LVDS encoder. This property is
> > +  valid for the first LVDS encoder D3 and E3 SoCs only, and points to the
> 
> ... on D3 ...
> 
> > +  second encoder to be used as a companion in dual-link mode.
> 
> Why restrict this to the first LVDS decoder, and not have a backlink in the
> other node,

Because there's no need to ? :-) Furthermore there's a need for the
master to know its a master, so have a link in a single direction is
pretty convenient. Otherwise I'd need an extra property to identify the
master.

> like for USB?

I'm not sure what USB does in that regard.

-- 
Regards,

Laurent Pinchart