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ERROR_MCA_MONITOR_VIOLATES_MCCS_SPECIFICATION
A compliance conclusion, not a complete diagnosis
This code says that the display violates the MCCS specification it claims to support. It is broader than a malformed capability string and broader than an invalid 0xDF version reply. The status does not identify the failing feature, command, or byte sequence by itself, so the decisive evidence is the exact API operation, the display's advertised MCCS revision, and the reply that Windows rejected.
Distinguish the nearby error families
| Situation | More specific status |
|---|---|
| The capability text cannot be parsed | ERROR_MCA_INVALID_CAPABILITIES_STRING |
The mccs_ver text and VCP 0xDF both exist but differ | ERROR_MCA_MCCS_VERSION_MISMATCH |
| The monitor reports a version outside the Windows API support range | ERROR_MCA_UNSUPPORTED_MCCS_VERSION |
| A returned technology enum is outside its valid set | ERROR_MCA_INVALID_TECHNOLOGY_TYPE_RETURNED |
How to make the report actionable
- Record the function name and all input values, especially the VCP code or high-level monitor operation being attempted.
- Capture the raw capabilities string and the VCP Version response from the same physical monitor, not from a similarly named display.
- Repeat the smallest failing request with the monitor connected directly when practical. This separates a display firmware claim from a path-specific control-channel problem without assuming either cause.
- Check whether the requested operation is advertised by
GetMonitorCapabilitiesor by the applicable VCP feature list before retrying it.
Many external displays implement only part of MCCS. Therefore a successful brightness read does not demonstrate that every feature, preset, or technology query is compliant. Avoid broad feature scans that change settings while collecting evidence.
References
- Microsoft: ERROR_MCA error definitions
- Microsoft: monitor configuration function groups
- VESA DDC/CI Standard
- ddcutil: MCCS feature terminology and revisions
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