HDMI uses the DDC I2C bus for communicating various bits of link status out of band with the actual HDMI video signal. This information can be useful for debugging issues like questionable cables sabotaged by feline teeth, Enthusiast Grade cables made of cow fencing wire, and other such problems that ruin one's media viewing plans.
Consequently, this series exposes various bits of pertinent information from the SCDC protocol in an HDMI connector's debugfs. To continually poll the link status, userspace can poll the debugfs file. --- Changes in v3: - Add patch to change return type of drm_scdc_read/write. - Rework error counter reading to duplicate less code. - Also check lane 3 counter valid flag when reading its error counter. - Use memset to clear buf for error counters, rather than doing it in the loop. - Make read_error_counters not accept 0 as num_lanes; fix it up in the caller instead. - Link to v2: https://patch.msgid.link/[email protected] Changes in v2: - Add HDMI 2.1 SCDC status reporting - Link to v1: https://patch.msgid.link/[email protected] To: Maarten Lankhorst <[email protected]> To: Maxime Ripard <[email protected]> To: Thomas Zimmermann <[email protected]> To: David Airlie <[email protected]> To: Simona Vetter <[email protected]> To: Andrzej Hajda <[email protected]> To: Neil Armstrong <[email protected]> To: Robert Foss <[email protected]> To: Laurent Pinchart <[email protected]> To: Jonas Karlman <[email protected]> To: Jernej Skrabec <[email protected]> To: Luca Ceresoli <[email protected]> To: Daniel Stone <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Nicolas Frattaroli <[email protected]> --- Nicolas Frattaroli (4): drm/scdc-helper: Don't use ssize_t return type for scdc_read/write drm/scdc-helper: Add scdc_status debugfs entry drm/display: bridge_connector: init scdc debugfs for HDMI drm/scdc-helper: Implement parsing and printing HDMI 2.1 fields drivers/gpu/drm/display/drm_bridge_connector.c | 4 + drivers/gpu/drm/display/drm_scdc_helper.c | 358 ++++++++++++++++++++++++- include/drm/display/drm_scdc.h | 9 + include/drm/display/drm_scdc_helper.h | 121 ++++++++- 4 files changed, 484 insertions(+), 8 deletions(-) --- base-commit: 587c82eb2067eff6f13385e1b7cf49fc6c3febbc change-id: 20260413-scdc-link-health-89326013d96c Best regards, -- Nicolas Frattaroli <[email protected]>
