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From: evans@syd.dit.CSIRO.AU (Bruce.Evans)
Newsgroups: comp.os.minix
Subject: Fix for 1.5.10 RS232 initialization (PC)
Message-ID: <1990Oct18.053903.23498@syd.dit.CSIRO.AU>
Date: 18 Oct 90 05:39:03 GMT
Organization: CSIRO Division of Info Tech, Sydney, Australia
Lines: 79

RS232 initialization was not reliable with some BIOS's (it worked better
after a cold boot). See the comments in the code to explain why.

#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#		"End of shell archive."
# Contents:  rs232.cdif rs232.crc
# Wrapped by evans@ditsydh on Thu Oct 18 15:34:40 1990
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'rs232.cdif' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'rs232.cdif'\"
else
echo shar: Extracting \"'rs232.cdif'\" \(1774 characters\)
sed "s/^X//" >'rs232.cdif' <<'END_OF_FILE'
X*** /tmp/1.5/kernel/rs232.c	Mon Apr  2 06:07:02 1990
X--- rs232.c	Mon Oct 15 04:38:35 1990
X***************
X*** 321,324 ****
X--- 321,329 ----
X    /* Set up the hardware to a base state, in particular
X     *	o turn off DTR (MC_DTR) to try to stop the external device.
X+    *	o be careful about the divisor latch.  Some BIOS's leave it enabled
X+    *	  here and that caused trouble (no interrupts) in version 1.5 by
X+    *	  hiding the interrupt enable port in the next step, and worse trouble
X+    *	  (continual interrupts) in an old version by hiding the receiver
X+    *	  port in the first interrupt.  Call rs_config() early to avoid this.
X     *	o disable interrupts at the chip level, to force an edge transition
X     *	  on the 8259 line when interrupts are next enabled and active.
X***************
X*** 326,336 ****
X     *	  mask, but there used to be trouble if the mask was set without
X     *	  handling a previous interrupt.
X-    *	o be careful about the divisor latch.  It may be enabled now, and
X-    *	  that used to cause trouble when interrupts were enabled too early
X-    *	  (see comment in rs_config()).  Call rs_config() early to avoid this.
X     */
X    istop(rs);			/* sets modem_ctl_port */
X-   out_byte(rs->int_enab_port, 0);
X    speed = rs_config(minor, DEF_BAUD, DEF_BAUD, LC_NO_PARITY, 1, 8, RAW);
X  
X    /* Clear any harmful leftover interrupts.  An output interrupt is harmless
X--- 331,338 ----
X     *	  mask, but there used to be trouble if the mask was set without
X     *	  handling a previous interrupt.
X     */
X    istop(rs);			/* sets modem_ctl_port */
X    speed = rs_config(minor, DEF_BAUD, DEF_BAUD, LC_NO_PARITY, 1, 8, RAW);
X+   out_byte(rs->int_enab_port, 0);
X  
X    /* Clear any harmful leftover interrupts.  An output interrupt is harmless
END_OF_FILE
if test 1774 -ne `wc -c <'rs232.cdif'`; then
    echo shar: \"'rs232.cdif'\" unpacked with wrong size!
fi
chmod +x 'rs232.cdif'
# end of 'rs232.cdif'
fi
if test -f 'rs232.crc' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'rs232.crc'\"
else
echo shar: Extracting \"'rs232.crc'\" \(58 characters\)
sed "s/^X//" >'rs232.crc' <<'END_OF_FILE'
X27260  20246 /tmp/1.5/kernel/rs232.c
X19451  20391 rs232.c
END_OF_FILE
if test 58 -ne `wc -c <'rs232.crc'`; then
    echo shar: \"'rs232.crc'\" unpacked with wrong size!
fi
chmod +x 'rs232.crc'
# end of 'rs232.crc'
fi
echo shar: End of shell archive.
exit 0
-- 
Bruce Evans		evans@syd.dit.csiro.au