i'm trying to debug a problem with the esp driver for the sbus FAS366
controller.  as the scsipi stuff trys to attach (?) the targets on
the scsi buss, a select with attention (SELATN cmd:0x42 + 1 byte msg)
is used along with a TEST UNIT READY (00h) command to test if a target
is there and ready.

[ncr53c9x_scsipi_request] [ncr53c9x_scsipi_request] [0x0, 6]->5 [ncr53c9x_sched]
 [ncr53c9x_select(t5,l0,cmd:0,tag:0,0)] <cmd:0x1 660>[wrfifo(7): c0 00 00 00 00
00 00]
<cmd:0x42 773>

this works, but i'm lost as to why the message-byte is written to the
FAS' fifo first?

also, any clue as to why that message-byte is for?  i can't find it in
either the FAS manual or SAM/SPC.

tia.
-heas