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List:       gpsd-dev
Subject:    [Gpsd-dev] Better test diff for serial.c
From:       gpsd-dev () lists ! berlios ! de (Eric S !  Raymond)
Date:       2006-06-14 13:58:23
Message-ID: 200606141358.k5EDwNar017718 () golux ! thyrsus ! com
[Download RAW message or body]

This is especially for Til to try:

--- serial.c	(revision 3335)
+++ serial.c	(working copy)
@@ -50,7 +51,7 @@
 void gpsd_set_speed(struct gps_device_t *session, 
 		   speed_t speed, unsigned char parity, unsigned int stopbits)
 {
-    speed_t	rate;
+    speed_t	rate, oldrate = cfgetispeed(&session->ttyset);
 
     if (speed < 300)
 	rate = B0;
@@ -73,7 +74,7 @@
     else
       rate =  B115200;
 
-    if (rate!=cfgetispeed(&session->ttyset) || (unsigned \
int)parity!=session->gpsdata.parity || stopbits!=session->gpsdata.stopbits) { +    if \
(rate!=oldrate || (unsigned int)parity!=session->gpsdata.parity || \
stopbits!=session->gpsdata.stopbits) {  
 	/*@ignore@*/
 	(void)cfsetispeed(&session->ttyset, rate);
@@ -145,10 +146,19 @@
 	 * flush followed by a 200-millisecond delay followed by flush has
 	 * been found to work reliably on the pl2303.  It is also known
 	 * from testing that a 100-millisec delay is too short, allowing
-	 * occasional failure to lock.
+	 * occasional failure to lock.  A straight delay of 500 milliseconds
+	 * without a following flush also seems to work; we don't know 
+	 * whether the second flush is doing something real to the state of 
+	 * the system or merely acting as an additional delay.
+	 *
+	 * The formula below tries to compute flush time for a device with
+	 * a 96-byte fifo like the pl2303.  10 is the actual number of bits
+	 * in an 8N1 serial frame.  At 4800bps this yields 200000.  For
+	 * higher speeds the delay will be less.
 	 */
+#define min(x, y)	((x) < (y) ? (x) : (y))
 	(void)tcflush(session->gpsdata.gps_fd, TCIOFLUSH);
-	(void)usleep(200000);
+	(void)usleep((1e6 / min(rate, oldrate)) * 10 * 96);
 	(void)tcflush(session->gpsdata.gps_fd, TCIOFLUSH);
     }
     gpsd_report(1, "speed %d, %d%c%d\n", speed, 9-stopbits, parity, stopbits);
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>

"Boys who own legal firearms have much lower rates of delinquency and
drug use and are even slightly less delinquent than nonowners of guns."
	-- U.S. Department of Justice, National Institute of
	   Justice, Office of Juvenile Justice and Delinquency Prevention,
	   NCJ-143454, "Urban Delinquency and Substance Abuse," August 1995.


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