[PATCH v2] iio: imu: st_lsm6dsx: Fix selection of ST_LSM6DS3_ID

[Stephan Gerhold <stephan@gerhold.net>]

At the moment, attempting to probe a device with ST_LSM6DS3_ID
(e.g. using the st,lsm6ds3 compatible) fails with:

    st_lsm6dsx_i2c 1-006b: unsupported whoami [69]

... even though 0x69 is the whoami listed for ST_LSM6DS3_ID.

This happens because st_lsm6dsx_check_whoami() also attempts
to match unspecified (zero-initialized) entries in the "id" array.
ST_LSM6DS3_ID = 0 will therefore match any entry in
st_lsm6dsx_sensor_settings (here: the first), because none of them
actually have all 12 entries listed in the "id" array.

Avoid this by additionally checking if "name" is set,
which is only set for valid entries in the "id" array.

Note: Although the problem was introduced earlier it did not surface until
commit 52f4b1f19679 ("iio: imu: st_lsm6dsx: add support for accel/gyro unit of lsm9ds1")
because ST_LSM6DS3_ID was the first entry in st_lsm6dsx_sensor_settings.

Fixes: d068e4a0f921 ("iio: imu: st_lsm6dsx: add support to multiple devices with the same settings")
Cc: <stable@vger.kernel.org> # 5.4
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
---
v1: https://lore.kernel.org/linux-iio/20191209170541.198206-1-stephan@gerhold.net/

Changes in v2:
  - Add Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
  - Add Fixes tag
  - Cc stable@vger.kernel.org
---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index a7d40c02ce6b..b921dd9e108f 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -1301,7 +1301,8 @@ static int st_lsm6dsx_check_whoami(struct st_lsm6dsx_hw *hw, int id,
 
 	for (i = 0; i < ARRAY_SIZE(st_lsm6dsx_sensor_settings); i++) {
 		for (j = 0; j < ST_LSM6DSX_MAX_ID; j++) {
-			if (id == st_lsm6dsx_sensor_settings[i].id[j].hw_id)
+			if (st_lsm6dsx_sensor_settings[i].id[j].name &&
+			    id == st_lsm6dsx_sensor_settings[i].id[j].hw_id)
 				break;
 		}
 		if (j < ST_LSM6DSX_MAX_ID)
-- 
2.24.1