SCO OpenServer

_entry(D2osdi)

_entry -- pass command through the SCSI host adapter to the device

Interfaces

SCSI host adapter drivers only.

Synopsis

   prefix_entry (register REQ_IO *req_p);

Description

The _entry( ) entry point routine passes the scsi_io_req(D4osdi) request block that was populated by the SCSI peripheral driver to the device.

Arguments

req_p: pointer to the SCSI request block, scsi_io_req(D4osdi)

Return values

Usage

An _entry( ) routine is required for all SCSI host adapters.

This routine is coded as a large switch statement that includes a case statement populated for each SCSI command that is documented on the scsi_io_req(D4osdi) manual page, plus other commands as required. These command blocks (or whatever data structure is appropriate; in some cases, just bytes or words) are then sent to the host adapter driver.

Most SCSI peripheral devices do not queue their I/O requests. Instead, the SCSI host adapter driver must be coded to handle an appropriate number of outstanding requests per configured target on the SCSI bus. The number of outstanding requests per configured target can be modified through the peripheral driver; by default, it is 5.

Context and synchronization

context

Hardware applicability

All

Version applicability

osdi: 1, 2, 3, 4, 5 SCSI host adapter drivers.

Differences between versions

External dependencies

Drivers that contain an _entry( ) routine must have an H in the second column of the mdevice(F) file to indicate that the driver is a SCSI host adapater.

References

scsi(HW) scsi_io_req(D4osdi)