user manual

Debugger General Information
3-12 Installation Guide
3
Disk I/O via 197Bug System Calls
All operations that actually access the disk are done directly or indirectly by
197Bug TRAP #496 system calls. (The command-level disk operations provide
a convenient way of using these system calls without writing and executing a
program).
The following system calls are provided to allow user programs to do disk
I/O:
Refer to the MVME197BUG 197Bug Debugging Package User’s Manual for
information on using these and other system calls.
To perform a disk operation, 197Bug must eventually present a particular disk
controller module with a controller command packet which has been
especially prepared for that type of controller module. (This is accomplished
in the respective controller driver module). A command packet for one type of
controller module usually does not have the same format as a command
packet for a different type of module. The system call facilities which do disk
I/O accept a generalized (controller-independent) packet format as an
argument, and translate it into a controller-specific packet, which is then sent
to the specified device. Refer to the system call descriptions found in the
MVME197BUG 197Bug Debugging Package User’s Manual for details on the
format and construction of these standardized “user” packets.
The packets which a controller module expects to be given vary from
controller to controller. The disk driver module for the particular hardware
module (board) must take the standardized packet given to a trap function
and create a new packet which is specifically tailored for the disk drive
controller it is sent to. Refer to documentation on the particular controller
module for the format of its packets, and for using the IOC command.
.DSKRD Disk read. System call to read blocks from a disk into
memory.
.DSKWR Disk write. System call to write blocks from memory onto a
disk.
.DSKCFIG Disk configure. This function allows the user to change the
configuration of the specified device.
.DSKFMT Disk format. This function allows the user to send a format
command to the specified device.
.DSKCTRL Disk control. This function is used to implement any special
device control functions that cannot be accommodated easily
with any of the other disk functions.