User guide

7: Host/ICP Interface
DC 900-1338I 127
token associated with the resource. If this is the case, the task can make a resource
request and obtain the token when it is released by XIO on completion.
7.2.3.2 Completion Status
Before processing the completion of the queue element, XIO stores a completion code
in the
status field of the node declaration header, as follows:
7.2.4 Host Request Queue Element
When your ICP-resident application or utility task posts a read or write request to the
host processor, it must create a queue element and post it to the appropriate node’s read
or write queue. The queue element consists of two buffers, a header buffer and a data
buffer. The header buffer contains a system buffer header followed by a host request
header. The next buffer (
sp_nxtb) field of the system buffer header in the header buffer
contains the address of the data buffer. The data buffer also contains a system buffer
header, followed by an ICP header, a protocol header, and the received data, if any, that
will ultimately be transferred to the application program (in the case of a write request),
or the area to which data being sent from the application program will be transferred
(in the case of a read request).
Figure 7–4 shows an example of a host request queue element with an encapsulated
data buffer.
0 = Good completion
1 = The node number is out of range or already declared
2 = A queue create system call failed (the queue ID is out of range
or the queue already exists)