Seems as though there are multiple bsg pass-throughs but
hardly any documentation (please correct me if I am wrong).
For example, in the kernel source Documentation sub-tree
"bsg" is only mentioned in one file:
    scsi/scsi_fc_transport.txt
and that is only a passing reference.

So I will start the ball rolling with some documentation
of using the bsg pass-through for the SAS Serial Management
Protocol (SMP). SMP is mainly used to access and control
SAS expanders. See the attached file.

Should this go in the kernel source Documentation subtree?
If so, where? My first guess would be Documentation/scsi .
Since it is SAS specific it could go in Documentation/scsi/sas .
Then again, bsg pass-throughs are not necessarily related to
SCSI so perhaps Documentation/block/bsg .

Has anyone else got some bsg pass-through documentation they
might like to contribute?

Doug Gilbert