Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] Missing validation of SCDC scrambling capabilities in HDMI atomic check, leading to atomic commit failure. - [Low] Kernel doc for `scrambler_needed` incorrectly claims it considers capabilities. --
commit 8506d2c44481f513bea9b489debfc6aacfc2b9a2 Author: Cristian Ciocaltea <[email protected]> drm/display: hdmi-state-helper: Set HDMI scrambling requirement This commit sets the drm_connector_hdmi_state.scrambler_needed flag when the computed TMDS character rate exceeds the HDMI 1.3 maximum limit. By centralizing this clock-based requirement in the HDMI state helper, it removes the need for drivers to open-code the threshold check. > diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c > b/drivers/gpu/drm/display/drm_hdmi_state_helper.c > index 69ccfbf123fe3..34e48e04d9712 100644 > --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c > +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c > @@ -592,6 +592,7 @@ hdmi_compute_clock(const struct drm_connector *connector, > return -EINVAL; > > conn_state->hdmi.tmds_char_rate = clock; > + conn_state->hdmi.scrambler_needed = (clock > > HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ); [Severity: High] Does this code fail to validate SCDC scrambling capabilities during atomic check? Setting scrambler_needed purely based on the clock rate, without validating if scrambling is actually supported by the sink and source, allows invalid atomic states to proceed. If an HDMI sink provides a buggy EDID reporting >= 340 MHz but without SCDC scrambling support (or the source lacks scrambling support), a mode requiring >340 MHz TMDS rate could be requested. hdmi_clock_valid() passes because info->max_tmds_clock doesn't reject it. Because hdmi_compute_clock() unconditionally sets scrambler_needed = true without checking if scrambling is actually supported by both source and sink, the atomic_check succeeds. Then, atomic_commit calls drm_connector_hdmi_enable_scrambling(), which checks capabilities, finds them lacking, and returns -EINVAL. Returning an error during the atomic commit phase violates the DRM atomic KMS contract. This leads to a state where the hardware might be partially programmed and the driver aborts the commit, which can cause black screens, driver state desync, or kernel warnings. [Severity: Low] Does this change make the kernel documentation for drm_connector_hdmi_state inaccurate? In include/drm/drm_connector.h, the kernel doc for scrambler_needed states it is computed from the capabilities: include/drm/drm_connector.h:drm_connector_hdmi_state /** * @scrambler_needed: Whether HDMI 2.0 SCDC scrambling is required * for the negotiated mode/bpc/format. * * Computed by drm_atomic_helper_connector_hdmi_check() from * @tmds_char_rate and the source/sink scrambling capabilities. But the implementation now only checks the clock against HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ, creating a documentation mismatch. > > return 0; > } -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=11
