linux-kernel - [PATCH] regcache: Use bsearch() to search the register defaults

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Date:	Tue,  4 Oct 2011 22:06:36 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
Cc:	patches@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: [PATCH] regcache: Use bsearch() to search the register defaults

Rather than open coding a binary search use the standard bsearch() using
the comparison function we're already using for sort() on insert. This
fixes a lockup I was observing due to iterating on min <= max rather
than min < max when we fail to look up.

Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
---
 drivers/base/regmap/regcache.c |   40 ++++++++++++++++++++--------------------
 1 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 18ab5b3..bf82783 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -13,6 +13,7 @@
 #include <linux/slab.h>
 #include <linux/export.h>
 #include <trace/events/regmap.h>
+#include <linux/bsearch.h>
 #include <linux/sort.h>
 
 #include "internal.h"
@@ -356,25 +357,7 @@ unsigned int regcache_get_val(const void *base, unsigned int idx,
 	return -1;
 }
 
-int regcache_lookup_reg(struct regmap *map, unsigned int reg)
-{
-	unsigned int min, max, index;
-
-	min = 0;
-	max = map->num_reg_defaults - 1;
-	do {
-		index = (min + max) / 2;
-		if (map->reg_defaults[index].reg == reg)
-			return index;
-		if (map->reg_defaults[index].reg < reg)
-			min = index + 1;
-		else
-			max = index;
-	} while (min <= max);
-	return -1;
-}
-
-static int regcache_insert_cmp(const void *a, const void *b)
+static int regcache_default_cmp(const void *a, const void *b)
 {
 	const struct reg_default *_a = a;
 	const struct reg_default *_b = b;
@@ -382,6 +365,23 @@ static int regcache_insert_cmp(const void *a, const void *b)
 	return _a->reg - _b->reg;
 }
 
+int regcache_lookup_reg(struct regmap *map, unsigned int reg)
+{
+	struct reg_default key;
+	struct reg_default *r;
+
+	key.reg = reg;
+	key.def = 0;
+
+	r = bsearch(&key, map->reg_defaults, map->num_reg_defaults,
+		    sizeof(struct reg_default), regcache_default_cmp);
+
+	if (r)
+		return r - map->reg_defaults;
+	else
+		return -1;
+}
+
 int regcache_insert_reg(struct regmap *map, unsigned int reg,
 			unsigned int val)
 {
@@ -397,6 +397,6 @@ int regcache_insert_reg(struct regmap *map, unsigned int reg,
 	map->reg_defaults[map->num_reg_defaults - 1].reg = reg;
 	map->reg_defaults[map->num_reg_defaults - 1].def = val;
 	sort(map->reg_defaults, map->num_reg_defaults,
-	     sizeof(struct reg_default), regcache_insert_cmp, NULL);
+	     sizeof(struct reg_default), regcache_default_cmp, NULL);
 	return 0;
 }
-- 
1.7.6.3

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