Status Blocks for Communications Device Handlers Overview

Status blocks are used to communicate status and exception information.

User-mode processes receive a status block whenever they request a CIO_GET_STAT operation. A user-mode process can wait for the next available status block by issuing a ddselect entry point with the specified POLLPRI event.

A kernel-mode process receives a status block through the stat_fn procedure. This procedure is specified when the device is opened with the ddopen entry point.

Status blocks contain a code field and possible options. The code field indicates the type of status block code (for example, CIO_START_DONE). A status block's options depend on the block code. The C structure of a status block is defined in the /usr/include/sys/comio.h file.

Additional device-dependent status block codes may be defined.