CAM/SIIS CAM_CMD_TIMEOUT hangs

[James R. Van Artsdalen]

I have problems with I/O hanging due to CAM/SIIS not handling the
CAM_CMD_TIMEOUT error.
Hangs happen every few hundred GB to every few TB.
The disks are behind SATA port multipliers.

This command un-hangs the drive and lets things run again:

# camcontrol reset all

I assume this is sending a soft reset to the disk drive but haven't
checked yet.

Is there a way xpt_done() or such might notice a CAM_CMD_TIMEOUT and
inject a "soft reset" request at the head of the I/O queue (to run
before the timed-out command retries)?