dove@mit-dspg@mit-mc (05/29/82)
From: dove at mit-dspg at mit-mc Tony Drogaris and I have succeeded in modifying our local tty device drivers (dh dz dhdm) to allow modem lines to be used for both incoming and outgoing calls without having to kill the init that normally waits for the incoming carrier. It works by using the 128 bit in the minor device number to indicate which direction is currently being used. Outgoing attempts to open when the line is in use ingoing fail with the EBUSY error. Ingoing attempts to open when the line is going out sleep until the line is closed and the carrier dropped, then until the carrier comes on again as usual. This stuff is fairly new, but seems to work and in the process some screwy code in our dz got fixed. This code will be made available to the bsd distrib people for future releases.