NAME

scsi − SCSI command interface

SYNOPSIS

­#S/id
­#S/0/cmd
­#S/0/data
­#S/0/debug
...

DESCRIPTION

The ­scsi interface is accessed through a two-level directory.  The single-byte ­id file contains the SCSI id of the host interface, typically 7.  Some implementations allow this to be changed by writing to the file; in many cases, the higher-order bits are hardware specific. 

Each SCSI target ­n (0≤n≤7) is associated with a subdirectory #S/n containing files cmd, data, and debug.  The following steps may be used to execute a SCSI command:

The command block is written to the ­cmd file. 

The ­data file is either written or read depending on the direction of the transfer.  (A command that involves no data transfer is executed with a zero-length write.) 

The ­cmd file is read to retrieve the status of the command, returned as a 4-byte big-endian integer. 

Writing an ASCII ­1 to the ­debug file causes tracing information to be written to /dev/klog; writing a ­0 turns the tracing off. 

SEE ALSO

hard(3)

Plan 9  —  January 03, 1993