Claude review: drm/rockchip: dw_hdmi_qp: Add support for HDMI overscan compensation

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Overall Series Review

Subject: drm/rockchip: dw_hdmi_qp: Add support for HDMI overscan compensation
Author: Alexey Charkov <alchark@flipper.net>
Patches: 6
Reviewed: 2026-06-04T12:35:00.723614

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This is a 2-patch series adding HDMI overscan compensation to the Rockchip dw_hdmi_qp driver. The approach is: (1) plumb pixel margins through `rockchip_crtc_state` so the VOP2 post-compositor scaler can use them instead of hard-coded 100% values, and (2) expose the standard DRM "overscan" TV property on the HDMI connector and convert the single percentage into per-side pixel margins in `atomic_check`.

The overall approach is reasonable and the code is small. There are several issues worth addressing:

**Major concern:** The use of `drm_mode_create_tv_properties_legacy()` is explicitly deprecated. The docstring in the kernel says *"New drivers must use drm_mode_create_tv_properties() instead."* This driver doesn't need analog TV mode selection, so calling the legacy function just to get the overscan property creates a bunch of unnecessary and misleading properties (subconnector, brightness, contrast, flicker reduction, saturation, hue, and the legacy mode selector). Only the overscan property is wanted.

**Moderate concern:** The early-return logic in `atomic_check` has a subtle interaction with margin changes. If the user changes the overscan percentage but the TMDS rate and BPC stay the same, the margins are computed and written to `s->tv_margins`, but `atomic_check` returns 0 without setting `s->output_mode`, `s->output_type`, or `s->output_bpc`. This works because those fields are preserved across state duplicates, but it means the CRTC state is modified without the function explicitly signaling that a modeset-level change occurred. The margins should probably also trigger a mode change to ensure the CRTC re-programs the post-scaler, though in practice `vop2_post_config` may be called on every commit regardless.

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