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Introduction to SCSI drivers

Host adapter communication with peripheral driver

The modular design of the SCSI interface allows any SCSI peripheral driver to work with any SCSI host adapter driver. This is accomplished by having a clearly-defined protocol between the SCSI peripheral driver tier and the SCSI host adapter tier.

Information about the I/O request is put into a scsi_io_req(D4osdi) structure that is populated by the SCSI peripheral driver's read(D2osdi), write(D2osdi), or ioctl(D2osdi) routine. This structure is then passed to the SCSI host adapter driver's _entry(D2osdi) routine, which arranges the actual I/O to or from the device. The SCSI host adapter hardware notifies the host adapter driver when the I/O operation is complete. The SCSI host adapter's intr(D2osdi) routine calls the SCSI peripheral driver's intr( ) routine (also called the callback funtion) to notify it that the I/O operation has completed, and the callback function either initiates another I/O operation and/or informs the user-level process that the I/O is completed.


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