Claude review: drm: detect panel type from DisplayID 2.x

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

Overall Series Review

Subject: drm: detect panel type from DisplayID 2.x
Author: Chenyu Chen <chen-yu.chen@amd.com>
Patches: 5
Reviewed: 2026-05-16T11:17:30.013253

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This 2-patch series adds DisplayID v2.x Display Parameters Data Block parsing to detect LCD vs OLED panels, and wires it into amdgpu_dm as a fallback panel type detection path. The general approach is sound: it fills a longstanding TODO in the amdgpu_dm code.

**However, there is a significant gap across the series:** `DRM_MODE_PANEL_TYPE_LCD` is added to the UAPI header (`drm_mode.h`) but:
1. The `drm_panel_type_enum_list` in `drm_connector.c` is not updated to include LCD, so the `panel_type` property enum doesn't recognize value 2.
2. The property-setting code at the end of `dm_set_panel_type()` is not updated to expose LCD — it only maps `PANEL_TYPE_OLED` → `DRM_MODE_PANEL_TYPE_OLED` and everything else → `DRM_MODE_PANEL_TYPE_UNKNOWN`.

This means a DID2-detected LCD panel will correctly set `link->panel_type = PANEL_TYPE_LCD` internally, but userspace will see `DRM_MODE_PANEL_TYPE_UNKNOWN` from the property, and the enum property likely cannot even accept value 2. The new UAPI constant is effectively dead code.

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