linux-kernel - Re: [PATCH 1/4] dt-bindings: display: panel: ili9881c: Add dsi-lanes property

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Message-ID: <frufdok3oxwgv4bk3v6jkeq5zwf3pheffk6qkweulmyye6epup@ucdefcuqwapx>
Date: Thu, 10 Apr 2025 12:33:35 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Kory Maincent <kory.maincent@...tlin.com>
Cc: Maxime Ripard <mripard@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: display: panel: ili9881c: Add dsi-lanes
 property

On Wed, Apr 09, 2025 at 11:28:46AM +0200, Kory Maincent wrote:
> On Tue, 8 Apr 2025 17:44:32 +0200
> Maxime Ripard <mripard@...nel.org> wrote:
> 
> > hi,
> > 
> > On Tue, Apr 08, 2025 at 05:27:00PM +0200, Kory Maincent wrote:
> > > Add the dsi-lanes property to specify the number of DSI lanes used by the
> > > panel. This allows configuring the panel for either two, three or four
> > > lanes.
> > > 
> > > Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
> > > ---
> > >  Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml | 5
> > > +++++ 1 file changed, 5 insertions(+)
> > > 
> > > diff --git
> > > a/Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml
> > > b/Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml
> > > index
> > > baf5dfe5f5ebdd92f460a78d0e56e1b45e7dd323..e36550616f6aac86c79832a48132ce8c11ebcf7a
> > > 100644 ---
> > > a/Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml +++
> > > b/Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml @@
> > > -27,6 +27,11 @@ properties: reg: maxItems: 1 
> > > +  dsi-lanes:
> > > +    description: Number of DSI lanes to be used must be <2>, <3> or <4>
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    enum: [2, 3, 4]
> > > +  
> > 
> > We have the data-lanes property for that already
> 
> Indeed but there is no such usage in panel bindings, only in bridge bindings.

It is expected that the DSI host sets mipi_dsi_device::lanes correctly.
If it is not the case, please fix the DSI host driver. The panel driver
can then use this data field in the probe function.

> 
> You are saying that I should add something like that:
>   port:                                                                        
>     $ref: /schemas/graph.yaml#/properties/port
> 
>     properties:                                                             
>       endpoint:                                                             
>         $ref: /schemas/media/video-interfaces.yaml#                         
>         unevaluatedProperties: false                                        
> 
>         data-lanes:
>           minItems: 2
>           maxItems: 4                                               
> 
> And use drm_of_get_data_lanes_count in the drivers.
> 
> If we do so, maybe this binding should land in panel-common.yaml instead?
> 
> Regards,
> -- 
> Köry Maincent, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com

-- 
With best wishes
Dmitry