From: Frank Mori Hess <fmhess@speakeasy.net>
Date: Mon, 21 Feb 2005 20:52:55 +0000 (+0000)
Subject: patch from Ian Abbott <abbotti@mev.co.uk>:
X-Git-Tag: r0_7_70~44
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=f40b0e226417334db8a7ad7b3c26498bbc6d6e90;p=comedi.git

patch from Ian Abbott <abbotti@mev.co.uk>:

Here's a couple more minor patches for the
i8253_cascade_ns_to_timer_2div function, which I should have spotted
earlier.

8253_dupcalc.patch gets rid of a duplicate calculation
8253_overflow.patch adds some arithmetic overflow checks to the "early
exit" test.
---

diff --git a/comedi/drivers/8253.h b/comedi/drivers/8253.h
index 97066b71..12f9ae44 100644
--- a/comedi/drivers/8253.h
+++ b/comedi/drivers/8253.h
@@ -133,9 +133,14 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
 	 * and execution) */
 	div1 = *d1 ? *d1 : 0x10000;
 	div2 = *d2 ? *d2 : 0x10000;
+	divider = div1 * div2;
 	if(div1 * div2 * i8253_osc_base == *nanosec &&
 		div1 > 1 && div1 <= 0x10000 &&
-		div2 > 1 && div2 <= 0x10000)
+		div2 > 1 && div2 <= 0x10000 &&
+		/* check for overflow */
+		divider > div1 && divider > div2 &&
+		divider * i8253_osc_base > divider &&
+		divider * i8253_osc_base > i8253_osc_base)
 	{
 		return;
 	}
@@ -160,7 +165,6 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
 				div2_glb = div2;
 			}
 			if (div2 <= 0x10000) {
-				ns = i8253_osc_base * div1 * div2;
 				if (ns >= *nanosec && ns < ns_lub) {
 					ns_lub = ns;
 					div1_lub = div1;