From: Trent Piepho <xyzzy@speakeasy.org>
Date: Wed, 11 Jul 2007 23:28:44 +0000 (-0300)
Subject: V4L/DVB (5832): ir-common: optimize bit extract function
X-Git-Tag: v2.6.23-rc1~493^2~12
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d67be61ebe5efaf9c4c11bf168781d678854c966;p=linux-2.6

V4L/DVB (5832): ir-common: optimize bit extract function

New code is simpler, shorter, compiles to about half the size, and is 2
to 4 times faster depending on how many bits in the mask are set.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
---

diff --git a/drivers/media/common/ir-functions.c b/drivers/media/common/ir-functions.c
index fcb1941356..fe447a06e2 100644
--- a/drivers/media/common/ir-functions.c
+++ b/drivers/media/common/ir-functions.c
@@ -107,21 +107,20 @@ void ir_input_keydown(struct input_dev *dev, struct ir_input_state *ir,
 }
 
 /* -------------------------------------------------------------------------- */
-
+/* extract mask bits out of data and pack them into the result */
 u32 ir_extract_bits(u32 data, u32 mask)
 {
-	int mbit, vbit;
-	u32 value;
+	u32 vbit = 1, value = 0;
+
+	do {
+	    if (mask&1) {
+		if (data&1)
+			value |= vbit;
+		vbit<<=1;
+	    }
+	    data>>=1;
+	} while (mask>>=1);
 
-	value = 0;
-	vbit  = 0;
-	for (mbit = 0; mbit < 32; mbit++) {
-		if (!(mask & ((u32)1 << mbit)))
-			continue;
-		if (data & ((u32)1 << mbit))
-			value |= (1 << vbit);
-		vbit++;
-	}
 	return value;
 }