Return to BSD News archive
Newsgroups: comp.unix.bsd
Path: sserve!manuel!munnari.oz.au!mips!decwrl!csus.edu!netcom.com!hasty
From: hasty@netcom.com (Amancio Hasty Jr)
Subject: Re: (386BSD) Modems and com ports
Message-ID: <x__nl1q.hasty@netcom.com>
Date: Fri, 21 Aug 92 02:53:29 GMT
Organization: Netcom - Online Communication Services (408 241-9760 guest)
References: <1992Aug20.171557.30071@watson.ibm.com> <1992Aug20.213721.4548@gateway.novell.com>
Keywords: internal or external?
Lines: 23
I think that if the com driver is strap to interrupt levels less than
disk level, then under heavy I/O activities the com drivers will drop
characters. If the com drivers is split into two parts:
(a) a routine at high level interrupt level less than splhigh and at
least as high as diskio that just collects the characters and queues
the requests to be processed at a lower priority.
(b) essential the same com driver that de-queues the request from its
higher level routine
If such a scheme is not implemented, it is conceivable that the system
may lock out spltty interrupts long enough for the uart to drop characters.
The above outlinde strategy has been implemented in Unix systems for pcs
with good results for instance the system being able to drive four
com ports at 9600 without dropping a single character.
Cheers,
Amancio Hasty