regmap: Return an error if a caller attempts to do an unsupported raw read

regmaps without raw I/O access can't implement raw I/O operations,
return an error if someone tries to do that rather than crashing.

Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 343263449aff..e2f68807d970 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2255,6 +2255,9 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 
         WARN_ON(!map->bus);
 
+        if (!map->bus || !map->bus->read)
+                return -EINVAL;
+
         range = _regmap_range_lookup(map, reg);
         if (range) {
                 ret = _regmap_select_page(map, &reg, range,