[PATCH] Fix divizion by zero in ad-hoc mode

This would happen if the card gets more than one management packet in a
jiffy.  Fix it by updating qual->qual at most once a second.
Measuremensts over a shorter period are meaningless anyway.
Signed-off-by: Pavel Roskin <proski@gnu.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/at76_usb.c b/at76_usb.c
index 59a5ed5..b3ed6fb 100644
--- a/at76_usb.c
+++ b/at76_usb.c
@@ -3202,9 +3202,15 @@ static void calc_qual(struct at76c503 *dev, struct at76c503_rx_buffer *buf, stru
 	   (dev->board_type == BOARDTYPE_503_INTERSIL_3863)) {
 	    qual->qual=buf->link_quality;
 	} else {
+	    unsigned long msec;
+
+	    /* Update qual at most once a second */
+	    msec = jiffies_to_msecs(jiffies) - dev->beacons_last_qual;
+	    if (msec < 1000)
+		return;
+
 	    qual->qual = qual->level * dev->beacons_received *
-	    		        dev->beacon_period /
-	                        (jiffies_to_msecs(jiffies) - dev->beacons_last_qual);
+			 dev->beacon_period / msec;
 		
 	    dev->beacons_last_qual = jiffies_to_msecs(jiffies);
 	    dev->beacons_received = 0;