DETERMINING EXTENDED CAPABILITY OF A CHANNEL PATH

A computer program product includes a tangible storage storing instructions for performing a method. The method includes: sending a request from a processing unit in a host computer system to a channel subsystem 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 and configured to control information transfer between the channel subsystem and the I/O device; and receiving channel path capability information by the processing unit, the capability information specified by a channel path description block including channel path identification and description information, the channel path description block specifying whether the channel path supports a Fibre Channel protocol for commanding an I/O operation, the channel path description block specifying whether the channel path supports an extension to the Fibre Channel protocol based on the channel path supporting the Fibre Channel protocol.