Related OSI fields

The OSI fields that are significant to this discussion are:

osi_asy1, which signifies Part 1
osi_asy2, which signifies Part 2
osi_asytok, which holds the LFS's token on entry to Part 1 and the PFS's token on entry to Part 2.
osi_ok2compimd, which indicates that the PFS may complete the operation immediately, if possible. See Asynchronous I/O flow details for details.
osi_compimd, which is returned by the PFS to indicate that it has completed the operation immediately. This is valid only if osi_ok2compimd is on.
osi_commbuff, which indicates that Part 2 of Async I/O must not occur. Within the PFS, the changes from normal Async I/O flow are:
1. Received data can be copied directly to the user's buffers from the PFS's inbound data handler.
2. osi_sched is called after the data has been copied.
3. The amount of data being returned must be supplied to osi_sched.
4. There must be no dependence on Part 2 being called.

Note: The last four fields are meaningful only when osi_asy1 or osi_asy2 are on; they should not be referred to otherwise.

These fields are covered in more detail in Figure 1.