Windows error 15204 (ERROR_MCA_UNSUPPORTED_MCCS

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The reported MCCS version is not supported by this API.

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ERROR_MCA_MCCS_VERSION_MISMATCH	ERROR_MCA_INTERNAL_ERROR

ERROR_MCA_UNSUPPORTED_MCCS_VERSION

Compatibility is decided by the API, not by the monitor alone

ERROR_MCA_UNSUPPORTED_MCCS_VERSION means that the Monitor Configuration API has recognized a reported MCCS revision outside the versions it supports. The Win32 error definition names MCCS 1.0, MCCS 2.0, and MCCS 2.0 Revision 1 as the supported set. A newer-looking capability string is therefore not automatically usable through this API, even when the display itself can answer DDC/CI requests.

Compare it with related statuses

ERROR_MCA_INVALID_VCP_VERSION means the VCP Version reply itself is invalid.
ERROR_MCA_MCCS_VERSION_MISMATCH means the capability-string version and VCP 0xDF report disagree.
This error means the reported revision is coherent enough to identify, but the Windows monitor API does not accept it as supported.

Appropriate next checks

Capture both version sources first: the mccs_ver section of the raw capability string and the VCP Version response. Then check the monitor vendor's supported control interface and firmware information. An application that only needs a small number of settings should not assume that forcing a different version string is harmless; revisions affect feature interpretation and supported values.

The wider MCCS ecosystem has revisions beyond the Windows API's stated range. ddcutil documents version history and notes that version 3.0 was not upward-compatible with 2.1 and did not gain broad industry adoption. That history helps explain why version labels cannot be treated as a simple greater-than comparison.

References

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