queue_depth tracking from LLD

[Christof Schmitt <christof.schmitt@de.ibm.com>]

I just came across the SCSI midlayer function scsi_track_queue_full.

If a SCSI command is returned with a status of QUEUE_FULL, then this
is mapped to ADD_TO_MLQUEUE and "device blocked". So, there is already
a mechanism in place. Is a LLD driver expected to additionally call
something like this to decrease the queue depth?

if (status_byte(scmd->result) == QUEUE_FULL)
	scsi_track_queue_full(sdev, sdev->queue_depth - 1))

If a LLD does this, should it also increase the queue depth again when
no more QUEUE_FULL status are seen? To me this looks like a
duplication of the midlayer device blocking, but i assume there is a
reason in having both, scsi_track_queue_full and the device blocking.

--
Christof Schmitt