[PATCH v2] dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports

[PATCH v2] dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports

[Marek Vasut]

The Lontium LT9211 is capable of 1..4 DSI lanes per input DSI port,
describe the lane count for each input port in the schema.

For example Linux kernel driver does already use that information and
fails to probe if it is missing.

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Robert Foss <rfoss@kernel.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: devicetree@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
---
V2: - Update commit message, indicate Linux already requires data-lanes property
    - Add required: data-lanes
---
 .../display/bridge/lontium,lt9211.yaml        | 43 ++++++++++++++++++-
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt9211.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt9211.yaml
index 9a6e9b25d14a9..7cfe92a8bcd72 100644
--- a/Documentation/devicetree/bindings/display/bridge/lontium,lt9211.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt9211.yaml
@@ -36,18 +36,56 @@ properties:
 
     properties:
       port@0:
-        $ref: /schemas/graph.yaml#/properties/port
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
         description:
           Primary MIPI DSI port-1 for MIPI input or
           LVDS port-1 for LVDS input or DPI input.
 
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes:
+                description: array of physical DSI data lane indexes.
+                minItems: 1
+                items:
+                  - const: 1
+                  - const: 2
+                  - const: 3
+                  - const: 4
+
+            required:
+              - data-lanes
+
       port@1:
-        $ref: /schemas/graph.yaml#/properties/port
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
         description:
           Additional MIPI port-2 for MIPI input or LVDS port-2
           for LVDS input. Used in combination with primary
           port-1 to drive higher resolution displays
 
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes:
+                description: array of physical DSI data lane indexes.
+                minItems: 1
+                items:
+                  - const: 1
+                  - const: 2
+                  - const: 3
+                  - const: 4
+
+            required:
+              - data-lanes
+
       port@2:
         $ref: /schemas/graph.yaml#/properties/port
         description:
@@ -99,6 +137,7 @@ examples:
             reg = <0>;
 
             endpoint {
+              data-lanes = <1 2 3 4>;
               remote-endpoint = <&dsi0_out>;
             };
           };
-- 
2.53.0

Re: [PATCH v2] dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports

[Krzysztof Kozlowski]

On Tue, Apr 07, 2026 at 10:31:03PM +0200, Marek Vasut wrote:
> The Lontium LT9211 is capable of 1..4 DSI lanes per input DSI port,
> describe the lane count for each input port in the schema.
> 
> For example Linux kernel driver does already use that information and
> fails to probe if it is missing.
> 
> Signed-off-by: Marek Vasut <marex@nabladev.com>

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

Claude review: dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports

[Claude Code Review Bot]

Overall Series Review

Subject: dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports
Author: Marek Vasut <marex@nabladev.com>
Patches: 2
Reviewed: 2026-04-12T13:19:34.040015

---

This is a single-patch v2 series adding `data-lanes` property definitions to the DSI input ports of the Lontium LT9211 devicetree binding. The pattern follows established conventions used by similar bridge bindings (e.g., `ti,sn65dsi83.yaml`). The switch from `$ref: /schemas/graph.yaml#/properties/port` to `$ref: /schemas/graph.yaml#/$defs/port-base` with `unevaluatedProperties: false` is the correct approach to allow additional endpoint properties.

The main concern is that the patch adds `required: - data-lanes` to port@0 and port@1, but these ports can serve multiple protocols (DSI, LVDS, or DPI). The `data-lanes` property is only meaningful for DSI, so unconditionally requiring it would make the binding reject valid LVDS/DPI devicetree descriptions. Notably, the ti,sn65dsi83 binding—which appears to be the template for this change—does **not** mark `data-lanes` as required, even though its ports are DSI-only.

---
Generated by Claude Code Patch Reviewer

Claude review: dt-bindings: display: bridge: lt9211: Require data-lanes on DSI input ports

[Claude Code Review Bot]

Patch Review

**Positive aspects:**

- The `port-base` + `unevaluatedProperties: false` refactoring is correct and follows the established pattern used by other bridge bindings.
- The `data-lanes` property definition with `const: 1..4` items is properly constraining lanes to sequential 1-based indexes, matching the hardware.
- The example update adding `data-lanes = <1 2 3 4>` is good and consistent with similar bindings.
- The commit message correctly notes the driver dependency at `drivers/gpu/drm/bridge/lontium-lt9211.c:688`:
  ```c
  dsi_lanes = drm_of_get_data_lanes_count(endpoint, 1, 4);
  ```
  which returns an error if missing (checked at line 697-698).

**Concern — `required: data-lanes` on multi-protocol ports:**

The port descriptions state that these ports serve multiple input protocols:

```yaml
      port@0:
        description:
          Primary MIPI DSI port-1 for MIPI input or
          LVDS port-1 for LVDS input or DPI input.
```

Yet the patch unconditionally requires `data-lanes`:

```yaml
            required:
              - data-lanes
```

`data-lanes` is a DSI-specific concept. If a DT describes the LT9211 with LVDS or DPI input, the binding would now force inclusion of `data-lanes`, which is semantically wrong for those protocols. DT bindings should describe the hardware, not just the current driver implementation.

The `ti,sn65dsi83.yaml` binding (lines 44-83) was clearly used as a template for this change, but it notably does **not** include `required: - data-lanes` on its DSI input ports. The patch is stricter than its reference.

**Recommendation:** Drop the two `required: - data-lanes` blocks from both port@0 and port@1. The property definition alone (without `required`) is sufficient to document and validate the property when present. If the intent is truly to make this mandatory for DSI configurations only, a conditional schema (e.g., `if/then` keyed on the presence of a DSI remote-endpoint) would be more correct, though likely overkill for this binding.

If the argument is "the driver requires it," the correct fix is documenting the property (which this patch does) and optionally fixing the driver to provide a reasonable default or a better error message, rather than encoding a driver requirement as a hardware constraint.

---
Generated by Claude Code Patch Reviewer