Claude review: dt-bindings: display: panel: add YAML schema for LXD M9189A

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Subject:** `[PATCH v3 2/3] dt-bindings: display: panel: add YAML schema for LXD M9189A`

**Review of binding file (lxd,m9189a.yaml):**

```yaml
+allOf:
+  - $ref: panel-common.yaml
```

**Positive:**
- Correctly references panel-common.yaml as base, which is the modern approach (changed in v3)
- Properties are properly documented
- Example is complete and compiles

**Issues identified:**

1. **Missing backlight requirement** (line 511-513):
```yaml
+  reset-gpios: true
+  power-supply: true
+  backlight: true
```

The binding declares `backlight: true` but doesn't include it in the `required:` section. However, the driver code at line 343-345 does this:

```c
+	ret = drm_panel_of_backlight(&m9189->panel);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to get backlight\n");
```

**Question:** Is backlight optional or required? If `drm_panel_of_backlight()` returns an error when backlight is missing, then it should be in the required list. If it's optional, the binding is correct but the error message might be misleading.

2. **Standby GPIO polarity** (line 538):
```yaml
+        standby-gpios = <&gpio5 22 GPIO_ACTIVE_LOW>;
```

The example shows `GPIO_ACTIVE_LOW`, but there's no documentation explaining what "standby" means for this panel. A description would help:

```yaml
  standby-gpios:
    description: GPIO used for the standby pin
    maxItems: 1
```

Consider adding more detail: "GPIO used to control panel standby mode. Assert to enter standby, de-assert for normal operation."

**Minor:** The example could use more descriptive node names, but this is very minor and matches common practice.

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Generated by Claude Code Patch Reviewer