regmap: Return a sensible error code if we fail to read the cache

If a register isn't cached then let callers know that so they can fall
back or error handle appropriately.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache-indexed.c

@@ -20,11 +20,10 @@ static int regcache_indexed_read(struct regmap *map, unsigned int reg,
 	int ret;
 
 	ret = regcache_lookup_reg(map, reg);
-	if (ret < 0)
-		*value = 0;
-	else
+	if (ret >= 0)
 		*value = map->reg_defaults[ret].def;
-	return 0;
+
+	return ret;
 }
 
 static int regcache_indexed_write(struct regmap *map, unsigned int reg,

drivers/base/regmap/regcache-lzo.c

@@ -232,7 +232,6 @@ static int regcache_lzo_read(struct regmap *map,
 	size_t blksize, tmp_dst_len;
 	void *tmp_dst;
 
-	*value = 0;
 	/* index of the compressed lzo block */
 	blkindex = regcache_lzo_get_blkindex(map, reg);
 	/* register index within the decompressed block */
@@ -261,7 +260,8 @@ static int regcache_lzo_read(struct regmap *map,
 	/* restore the pointer and length of the compressed block */
 	lzo_block->dst = tmp_dst;
 	lzo_block->dst_len = tmp_dst_len;
-	return 0;
+
+	return ret;
 }
 
 static int regcache_lzo_write(struct regmap *map,

drivers/base/regmap/regcache-rbtree.c

@@ -193,8 +193,7 @@ static int regcache_rbtree_read(struct regmap *map,
 		*value = regcache_rbtree_get_register(rbnode, reg_tmp,
 						      map->cache_word_size);
 	} else {
-		/* uninitialized registers default to 0 */
-		*value = 0;
+		return -ENOENT;
 	}
 
 	return 0;

drivers/base/regmap/regcache.c

@@ -378,7 +378,7 @@ int regcache_lookup_reg(struct regmap *map, unsigned int reg)
 	if (r)
 		return r - map->reg_defaults;
 	else
-		return -1;
+		return -ENOENT;
 }
 
 int regcache_insert_reg(struct regmap *map, unsigned int reg,