regmap: verify if register is writeable before writing operations

regmap provides a couple of ways to validate the register range used.
a) maxim allowed register, b) writable/readable register tables,
c) callback function that can be provided by the driver to validate
a register. regmap framework should verify if registers
are writeable before every write operation. However this doesn't
seems to happen in every situation.

The method `_regmap_raw_write_impl` is only using the `writeable_reg`
callback to verify if register is writeable, ignoring the other two.
This can lead to undefined behaviour since this allows to write to
registers that could be declared un-writeable by using any other
option.

Change `_regmap_raw_write_impl` to use the `regmap_writeable` method
to verify if registers are writable before the write operation.
Signed-off-by: NNandor Han <nandor.han@vaisala.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/base/regmap/regmap.c

@@ -1493,11 +1493,10 @@ static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 	WARN_ON(!map->bus);
 
 	/* Check for unwritable registers before we start */
-	if (map->writeable_reg)
-		for (i = 0; i < val_len / map->format.val_bytes; i++)
-			if (!map->writeable_reg(map->dev,
-					       reg + regmap_get_offset(map, i)))
-				return -EINVAL;
+	for (i = 0; i < val_len / map->format.val_bytes; i++)
+		if (!regmap_writeable(map,
+				     reg + regmap_get_offset(map, i)))
+			return -EINVAL;
 
 	if (!map->cache_bypass && map->format.parse_val) {
 		unsigned int ival;