Claude review: drm/amd/display: use DisplayID panel type in dm_set_panel_type

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

Patch Review

**Placement of the DID2 fallback — correct.**

The new check is inserted after VSDB + DPCD and before the Samsung heuristic, which matches the priority the TODO comment described:

```c
/* If VSDB and DPCD didn't determine panel type, check DID */
if (link->panel_type == PANEL_TYPE_NONE) {
    if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_LCD)
        link->panel_type = PANEL_TYPE_LCD;
    else if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_OLED)
        link->panel_type = PANEL_TYPE_OLED;
}
```

This correctly gates on `PANEL_TYPE_NONE`, so higher-priority detection (VSDB, DPCD) is not overridden.

**Bug: property-setting code not updated for LCD.**

The existing code at the end of `dm_set_panel_type()` (untouched by this patch) is:

```c
if (link->panel_type == PANEL_TYPE_OLED)
    drm_object_property_set_value(&connector->base,
        adev_to_drm(adev)->mode_config.panel_type_property,
        DRM_MODE_PANEL_TYPE_OLED);
else
    drm_object_property_set_value(&connector->base,
        adev_to_drm(adev)->mode_config.panel_type_property,
        DRM_MODE_PANEL_TYPE_UNKNOWN);
```

If DID2 detects LCD, `link->panel_type` becomes `PANEL_TYPE_LCD` (value 1 from `dc_types.h`). This falls into the `else` branch, and the userspace-visible property is set to `DRM_MODE_PANEL_TYPE_UNKNOWN`. The LCD detection works internally within the driver but is invisible to userspace.

This should be updated to also handle `PANEL_TYPE_LCD`:

```c
if (link->panel_type == PANEL_TYPE_OLED)
    ...DRM_MODE_PANEL_TYPE_OLED;
else if (link->panel_type == PANEL_TYPE_LCD)
    ...DRM_MODE_PANEL_TYPE_LCD;
else
    ...DRM_MODE_PANEL_TYPE_UNKNOWN;
```

**Style nit: mixing UAPI and internal constants in the comparison.**

```c
if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_LCD)
    link->panel_type = PANEL_TYPE_LCD;
```

This compares a `DRM_MODE_PANEL_TYPE_*` (UAPI) value against the same namespace and assigns a `PANEL_TYPE_*` (DC internal) value. It works because the values happen to map correctly, but it couples the driver to the UAPI constants. The `did_panel_type` field in `drm_display_info` uses UAPI constants by design (it's DRM core), so this cross-namespace mapping is unavoidable here. Just be aware that if either namespace is reordered independently, this breaks silently.

**Overall:** The fallback logic is correct and well-placed. The missing property-setting update for LCD is the main issue that should be fixed before merging.

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Generated by Claude Code Patch Reviewer