iio: maxim_thermocouple: detect invalid storage size in read()

As found by gcc -Wmaybe-uninitialized, having a storage_bytes value other
than 2 or 4 will result in undefined behavior:

drivers/iio/temperature/maxim_thermocouple.c: In function 'maxim_thermocouple_read':
drivers/iio/temperature/maxim_thermocouple.c:141:5: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This probably cannot happen, but returning -EINVAL here is appropriate
and makes gcc happy and the code more robust.

Fixes: 10f5ee3c74fa ("iio: maxim_thermocouple: Align 16 bit big endian value of raw reads")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
(cherry picked from commit 32cb7d27e65df9daa7cee8f1fdf7b259f214bee2)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/temperature/maxim_thermocouple.c b/drivers/iio/temperature/maxim_thermocouple.c
index 066161a4bccd90e7df35fd0c20e2648dee551a18..f962f31a5eb223c4f41d273743ed75f30e648a18 100644 (file)
--- a/drivers/iio/temperature/maxim_thermocouple.c
+++ b/drivers/iio/temperature/maxim_thermocouple.c
@@ -136,6 +136,8 @@ static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
                ret = spi_read(data->spi, (void *)&buf32, storage_bytes);
                *val = be32_to_cpu(buf32);
                break;
+       default:
+               ret = -EINVAL;
        }
 
        if (ret)