NAME

gd − ISI SCSI hard disk driver

SYNOPSIS

GD0 at address 000ffffc0 vector 0x78 level 6
GD0 at ∗∗∗ no address ∗∗∗ no vector

DESCRIPTION

The driver supports all four possible SCSI-U boards, as well as SCSI drive target devices in id positions 0-3.  It also supports up to two logical units (drives) per device. 

The GD devices are used like any other disk drives. 

The flag qi_flags&1 disables the use of disconnect/reconnect, which is enabled on all devices by default. 

The GD devices also support an ioctl call (defined in <sys/gdio.h>) to enable/disable the use of the disconnect/reconnect by the drives.  This call overrides the qi-flag. 

The SCSI-U hardware byte-swaps all data sent to disk.  Byte-swapping medium data poses no problem, because the data will be byte-swapped again when it is read from the disk, but byte-swapping command data renders commands unintelligible.  Therefore, the SCSI-U firmware automatically byte-swaps command data before sending it to the device, ensuring that it will be read properly after the SCSI-U hardware byte-swaps it again. 

You can control software byte-swapping with two flags:  qi_flags&2 and qi_flags&4.  When these flags are sent to 0, command data is byte-swapped by the SCSI-U firmware before being sent to the device, but medium data is not. 

Setting qi-flags&2 to 1 disables software byte-swapping of command data.  This flag must be set to 0 when using the SCSI-U. 

Setting qi-flags&4 to 1 enables software byte-swapping of medium data.  The data will be byte-swapped twice, slowing down transfers, but making the stored data readable by other controllers or CPUs. 

DISK SUPPORT

The GD devices provide standard disk access to a variety of hard disk drives, many floppy drives, and removable disk drives. 

FILES

[r]gd{0-31}{a-h}

GD Minor Device Number Construction:

bitUNIX and Standalone Function
0-2drive partition (a-h)
3logical unit number
4-5SCSI target device id number
6-7SCSI bus (SCSI-U controller) number

SEE ALSO

gg(4i), gdbad(8i), scsimon(8i)

DIAGNOSTICS

gd%d%c: hard error bn%d.  An unrecoverable error occurred during transfer of the specified sector of the specified disk partition.  The error was unrecoverable.  A large number of retry attempts (including offset positioning and drive recalibration) could not recover the error. 

gd%d: not ready.  The drive was spun down or off line when it was accessed.  The I/O operation is not recoverable. 

gd%d%c: soft bn%d.  A recoverable ECC error occurred on the specified sector in the specified disk partition.  Check to see if certain cylinders on the pack, spots on the carriage of the drive or heads are indicated. 

BUGS

In raw I/0 read(2) and write(2) truncate file offsets to 512-byte block boundaries, and write(2) scribbles on the tail of incomplete blocks.  Thus, in programs that are likely to access raw devices, read(2), write(2), and lseek(2) should always deal in 512-byte multiples. 

4th Berkeley Distribution  —  15 April 1988