|
|
If a SCSI command returns CHECK CONDITION status from the peripheral, the host adapter driver is responsible for sending a REQUEST SENSE command to return the sense data from the failed command. (Some adapter boards do this automatically.)
The host adapter driver can use
scsi_sense and sense_len members
in the request block for the sense data,
or can place the sense data
in the request block after the SCSI command
that caused the error.
By default,
fourteen bytes of data are returned,
with the first byte following the last byte of the
command in the SCSI CDB.
Host adapters that support extended sense data
can return up to 255 bytes.
As an example, the SCSI peripheral driver could access the first byte of the returned sense data with the following expression:
request.scsi_cmd.raw[request.cmdlen]Note that some early versions of the SCSI interface did not support the use of the
scsi_sense and sense_len members
of the request block.