• Implementation: https://github.com/petabyt/chdk/blob/23c1f3f04fa1c7d483083d403818972a739c6dfd/core/ptp.c#L443
• Opcode: 0x9999

All functionality is switched from a code in the first parameter: https://github.com/petabyt/chdk/blob/23c1f3f04fa1c7d483083d403818972a739c6dfd/core/ptp.h#L33C1-L33C1

TODO: Document CHDK extensions