User`s manual

Disk I/O Support

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initiate the transfer. If the conversion from blocks to sectors yields

a fractional sector count, an error is returned and no data is

transferred.

Device Probe

A device probe with entry into the device descriptor table is done

whenever a specified device is accessed. This happens when system

calls .DSKRD, .DSKWR, .DSKCFIG, .DSKFMT, and .DSKCTRL,

and commands IOC, IOP, IOT, MAR, MAW, and PBOOT are

used.

The device probe mechanism utilizes the SCSI commands Inquiry

and Mode Sense. If the specified controller is non-SCSI, the probe

simply returns a status of device present and unknown. The device

probe makes an entry into the device descriptor table with the

pertinent data. After an entry has been made, the next time a probe

is done it simply returns with device present status (pointer to

the device descriptor).

Disk I/O via Debugger Commands

The following debugger commands are provided for disk I/O.

Refer to Chapter 3 for instructions for their use. When a command

is issued to a particular controller LUN and device LUN, these

LUNs are remembered in the debugger so that the next disk

command uses the same controller and device.

IOI (Input/Output Inquiry)

The IOI command is used to probe the system for all possible

CLUN/DLUN combinations and display inquiry data for devices

which support it. The device descriptor table only has space for 16

device descriptors. With the IOI command, you can view the table

and clear it if necessary.