ioctl(~CRMOD) mungs last character in queue

[Dave Martindale]

What sort of device are you using to drive the serial line which talks to
the Spinwriter?  The "wait until output drains" feature of ioctl probably
just waits **until the last character has been sent to the device**.
At that point in time, the second-last character is being transmitted and
the last character is almost certainly just sitting in a holding register
somewhere.  If the driver then handles the change to CRMOD by doing
something which changes some of the device's control registers, which
may flush or clobber this buffer, you could lose the last character.
The problem may be in either the hardware itself or the driver.