From mboxrd@z Thu Jan  1 00:00:00 1970
From: Claude Code Review Bot <claude-review@example.com>
To: dri-devel-reviews@example.com
Subject: Claude review: drm/display: hdmi-state-helper: Try subsampling in mode_valid
Date: Sun, 12 Apr 2026 11:01:41 +1000
Message-ID: <review-patch7-20260409-color-format-v12-7-ce84e1817a27@collabora.com>
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References: <20260409-color-format-v12-0-ce84e1817a27@collabora.com> <20260409-color-format-v12-7-ce84e1817a27@collabora.com>
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Patch Review

Fixes `drm_hdmi_connector_mode_valid()` to not reject 420-only/420-also modes:

```c
if (drm_mode_is_420_only(&connector->display_info, mode)) {
	if (connector->ycbcr_420_allowed)
		fmt = DRM_OUTPUT_COLOR_FORMAT_YCBCR420;
	else
		return MODE_NO_420;
} else if (drm_mode_is_420_also(&connector->display_info, mode) &&
	   connector->ycbcr_420_allowed) {
	fmt = DRM_OUTPUT_COLOR_FORMAT_YCBCR420;
} else {
	fmt = DRM_OUTPUT_COLOR_FORMAT_RGB444;
}
```

This is a real bug fix (has `Fixes:` tag). The 420-also path is slightly aggressive -- it always picks YUV420 for 420-also modes when the connector supports it, even though the mode would work fine in RGB. However, for `mode_valid` this is conservative (accepting more modes), and the actual format is chosen later in `hdmi_compute_config`. So this is correct.

R-b from both Maxime Ripard and Dmitry Baryshkov.

**Verdict**: Good.

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