AHA-2940, CHECK_CONDITION

[Doug Ledford]

--------
> 
> >  I'm developing a user level interface with the generic scsi driver 
> > sg.c under linux-2.0.29.
> > 
> >  The target scsi device attached to my aha-2940 returns 
> > CHECK_CONDITION (0x02) to indicate an abnormal, but not fatal
> > event.
> >
> >  When I check the result from the scsi transaction, this status is
> > set to 0, and there is no sense information (there should be).
> 
> The aic7xxx driver (and other drivers too) automatically request
> the sense information upon a check condition.  Check the sense
> buffer in the SCSI command for non-zero which is what I believe
> the mid-level SCSI code does.  

Of course, we also set the aic7xxx_error(cmd) = DID_ERROR (mapped from 
DID_RETRY_COMMAND).  This very well could be causing the mid level code to 
retry the command instead of passing the sense up to the calling party.  It 
may be more appropriate to do something like this:

in aic7xxx_handle_seqint()
  in case CHECK_CONDITION:
    if (aic7xxx_error(cmd) == DID_OK)
    {
      aic7xxx_error(cmd) = DID_ERROR | ((DRIVER_SENSE | SUGGEST_DIE) << 8);
    }

or possibly (in the same place):
      aic7xxx_error(cmd) = DID_ERROR | ((DRIVER_SENSE | SUGGEST_SENSE) << 8);

Some experimentation to see what actually returns the sense information to 
the responsible party may be in order.  Sounds like slimmer at fnal.gov is the 
perfect test candidate.

One further note, the aic7xxx code in 2.0.29 is old, in it the target line 
is actually in aic7xxx_isr(), same case situation though.
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