Command capabilities

Syntax: capabilities <display-selection-options>

Reports the monitor's capabilities string. This string describes, among other things, the VCP Features that the monitor supports and, for non-continuous features where appropriate, the allowed values.

In practice, the capabilities string is often inaccurate. Therefore ddcutil simply presents the string. It does not use the capabilities string when formulating commands and interpeting responses. This is for multiple reasons:

  • A DDC capabilities request requires multiple I2C exchanges, making it both slow and unreliable. Because of its complexity, it is particularly vulnerable to I2C errors. On monitors with paticularly poor I2C implementations it sometimes fails because the maximum number of I2C retries is exceeded.

  • There is no capabilities request defined in the programming interface for USB connected monitors. ddcutil simulates a capabilities response by looking at what USB HID reports exist for feature codes.

  • The response to the DDC capabilities API request may be incorrect. For example, the capabilities response from the HP LP2480zx monitor does not list VCP feature code x10 (brightness) as supported. However, feature code x10 is in fact supported. The only way to know for sure if a monitor implememts a VCP feature code is to try it.

Note however, that ddcui does make use of the the capabilities string.

By default the capabilities command displays the capabilities string in parsed form.

Option: --terse

Display the unparsed capabilities string.

Option: --verbose

Display both the unparsed string and its parsed form.