The
wdsc driver provides an abstraction layer between the SCSI hardware found in multitudinous SGI machines (including Personal Iris series, Indigo, Indy, Challenge S, Indigo2, and Challenge M) and the machine independent SCSI drivers described in
scsibus(4).
In addition to sending the required SCSI commands to target devices on the SCSI bus, the
wdsc driver deals with DMA, device interrupts, sync/async negotiation, and target disconnects/reconnects.