Special Files

There are two separate interfaces to the serial optical link device handler. The special file /dev/ops0 provides access to the optical port subsystem. An application that opens this special file has access to all the ports, but it does not need to be aware of the number of ports available. Each write operation includes a destination processor ID. The device handler sends the data out the correct port to reach that processor. In case of a link failure, the device handler uses any link that is available.

The /dev/op0, /dev/op1, ..., /dev/opn special files provide a diagnostic interface to the serial link adapters and the serial optical channel converters. Each special file corresponds to a single optical port that can only be opened in Diagnostic mode. A diagnostic open allows the diagnostic ioctls to be used, but normal reads and writes are not allowed. A port that is open in this manner cannot be opened with the /dev/ops0 special file. In addition, if the port has already been opened with the /dev/ops0 special file, attempting to open a /dev/opx special file will fail unless a forced diagnostic open is used.