Re: [PATCH] dt-bindings: display: panel: Make DSI panels port optional

[Dmitry Baryshkov]

On Wed, Nov 11, 2026 at 01:31:39PM +0100, Krzysztof Kozlowski wrote:
> On 11/11/2026 13:30, Krzysztof Kozlowski wrote:
> > On 11/11/2026 12:13, Maxime Ripard wrote:
> >> On Wed, Nov 11, 2026 at 12:03:39PM +0100, Krzysztof Kozlowski wrote:
> >>> DSI panels can be placed under DSI bus directly and many Linux DRM
> >>> drivers will work fine with it: mipi_dsi_host_register() adds device for
> >>> such panel and DRM driver does not use OF graph to configure lanes.
> >>
> >> That's not true. We do use the endpoints to configure the lanes through
> >> the data-lanes property. See drm_of_get_data_lanes*
> > 
> > Some drivers use endpoints, some not. As discussed on other thread,
> > there are more than which do not.
> 
> "there are more than one which do not."

Which means that those should be fixed. We have legacy cases where the
drivers assumed that, but we should not target legacy.

> 
> > 
> >>
> >>> The affected here Linux panel drivers do not use OF graph, either.
> >>>
> >>> Requiring graph port for such panels is tying the binding to one
> >>> specific implementation of Linux DRM drivers, e.g. Qualcomm DRM which
> >>> requires the port.  The port is not needed for the hardware to operate
> >>> and for some of the Linux drivers, so it should be optional.
> >>>
> >>> Suggested-by: Romain TISSERAND <romain.tisserand@xxxxxxxxx>
> >>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>
> >>
> >> DSI busses can handle multiple devices, and multiple data types. If we
> >> were to drop the port node, how does the upstream video device know
> >> which device it should send its video output to?
> >>
> > 
> > We do not drop the port node, who suggested that?
> > 
> > You do get, that we are not talking about the DSI host, but the panel?

The panel might be driven by the host directly or there can be other
chips on the bus (someboby has been asking about the retimer or
something else sitting on the DSI bus between the host and the panel).

-- 
With best wishes
Dmitry