Determining extended capability of a channel path

A computer program product includes a tangible storage storing instructions for performing a method. The method includes: receiving a request at a channel subsystem in a host computer system to provide a channel path description for a channel path, the channel subsystem including a channel configured to be coupled to a control unit via the channel path, the channel configured to control information transfer over the channel path; and outputting a channel path description block from the channel subsystem to the operating system in response to the request, the channel path description block including channel path identification and description information, the channel path description block specifying whether the channel path supports a Fiber Channel protocol for commanding an I/O operation, the channel path description block specifying whether the channel path supports an extension to the Fiber Channel protocol based on the channel path supporting the Fiber Channel protocol.