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From: grossman@bbn.com (Martin Grossman)
Newsgroups: comp.os.minix
Subject: modems and carrier detect under minix 1.5.10 IBM/XT
Keywords: modem, DCD
Message-ID: <62684@bbn.BBN.COM>
Date: 12 Feb 91 17:12:29 GMT
Sender: news@bbn.com
Lines: 29


Hi there,

I've been fiddling with getting my modem on COM1 to work properly!!!

1) Minix doesn't examine the DCD line from the modem
	So I added some code in getty to do a port_in(0x03f8+6,&val)
	and then examine bit 7.  Now I can see DCD.
2) Minix does enable all interrupts from the UART
	When the DCD line changes state it causes an interrupt
	that minix gets real fast and doesn't do anything with it,
	thus I can never see the other bit (I think its bit 3)
	that states that DCD changed states.
3) I've hacked up getty and login as follows:
	a) added some code before call to do_carier() to:
		set -ECHO & RAW
		output at\r
		delay
		output +++
		delay
		output ath\r
	b) defined CHOISE_A to examine DCD via doing a port_in()
	c) added timeouts (via sig #14) to correctly timeout both getty
	   and login if idle for too long.

4) TODO
	fix the kernel to
	a) do carrier correctly
	b) send signal to process if its not getty and DCD went down.