dial in/out lines for modems summary wanted

[System Administrator]

I'm seeking a summary of the implementation ideas which were discussed on
the net regarding the implementation of shared dial in/out lines for modem
use.  The concept I am seeking to implement is that which uses separate
minor device numbers for identifying in- and outgoing modem-line devices.

I recall the discussion of this method using the following scheme:

	incoming:	If line is free and a carrier is detected, open
			the line, prevent use by an outgoing-open.  If
			the line is in use by an outgoing, regardless
			of carrier state, sleep.

	outgoing:	If line is free, regardless of carrier, open the
			line and prevent use by the incoming device node.
			If the line is in use, fail.

Mentions of using ttyMn and ttymn for modem lines with respect to their
usage (incoming/outgoing) was also suggested.  Is there a common naming
mechanism followed using this convention?

I intend to implement this method in both DZ, DL and DH type drivers.  Any
summarization to help avoid oversights and errors would be appreciated.
-- 
Scott G. Taylor       Pmd Resources, 3709 Old Conejo Rd, Newbury Park, CA 91320
snidely!mutley!staylor at wlbr.eaton.com                            (805) 499-0367
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