- We should return error = 0 and the upper processing would   return a zero length read. Otherwise we don't return the   right error indication.
- We should return error = 0 and the upper processing would
  return a zero length read. Otherwise we don't return the
  right error indication.

Approved by:	re@freebsd.org (gnn)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase