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.
The following are the six common status codes:
Additional device-dependent status block codes may be defined.
This block is provided by the device handler when the CIO_START operation completes:
| option[0] | The CIO_OK or CIO_HARD_FAIL status/exception code from the common or device-dependent list. |
| option[1] | The low-order two bytes are filled in with the netid field. This field is passed when the CIO_START operation is invoked. |
| option[2] | Device-dependent. |
| option[3] | Device-dependent. |
This block is provided by the device handler when the CIO_HALT operation completes:
| option[0] | The CIO_OK status/exception code from the common or device-dependent list. |
| option[1] | The low-order two bytes are filled in with the netid field. This field is passed when the CIO_START operation is invoked. |
| option[2] | Device-dependent. |
| option[3] | Device-dependent. |
The following block is provided when the physical device handler (PDH) is finished with a transmit request for which acknowledgment was requested:
| option[0] | The CIO_OK or CIO_TIMEOUT status/exception code from the common or device-dependent list. |
| option[1] | The write_id field specified in the write_extension structure passed in the ext parameter to the ddwrite entry point. |
| option[2] | For a kernel-mode process, indicates the mbuf pointer for the transmitted frame. |
| option[3] | Device-dependent. |
This block is returned whenever a status block is requested but there are none available:
| option[0] | Not used |
| option[1] | Not used |
| option[2] | Not used |
| option[3] | Not used |
This block is returned once after one or more status blocks is lost due to status queue overflow. The CIO_LOST_STATUS block provides the following:
| option[0] | Not used |
| option[1] | Not used |
| option[2] | Not used |
| option[3] | Not used |
This status block is used to return status and exception codes that occur unexpectedly:
| option[0] | The CIO_HARD_FAIL or CIO_LOST_DATA status/exception code from the common or device-dependent list |
| option[1] | Device-dependent |
| option[2] | Device-dependent |
| option[3] | Device-dependent |
The ddwrite entry point, ddselect entry point.
The CIO_HALT operation, CIO_GET_STAT operation, CIO_START operation.
Common Status/Exception Codes.