henry (03/18/83)
>From some observations last night, I think I know what's been causing
a persistent Sanders problem: seemingly-spontaneous paper misalignment
by a couple of lines, appearing at random times. It appears to happen
when a new Sanders job comes ready for printing just as the previous
one is finishing. This may be yet another effect of a known problem:
when the daemon dies (closing /dev/sp as it goes), the software loses
track of the XON/XOFF handshaking the Sanders is doing. This problem
causes the foulups that happen if the printer is offline when a job
arrives.
I have kludged around the problem temporarily, by adding /dev/sp to
the list of the things that /lib/update holds open permanently. This
required a minor change to the Sanders daemon to make it refrain from
trying to set the exclusive-access bit on the device. The proper fix
is to stop running the Sanders via the tty driver, i.e. give it a
custom driver that is smart enough to continue monitoring the XON/XOFF
handshaking even when nobody has it open. That will take a bit of
work; we'll see if the /lib/update kludge fixes the problem for the
moment first.