[PATCH v2] iio: imu: bmi160: Remove potential undefined behavior in bmi160_config_pin()

[Josh Poimboeuf <jpoimboe@kernel.org>]

If 'pin' is not one of its expected values, the value of
'int_out_ctrl_shift' is undefined.  With UBSAN enabled, this causes
Clang to generate undefined behavior, resulting in the following
warning:

  drivers/iio/imu/bmi160/bmi160_core.o: warning: objtool: bmi160_setup_irq() falls through to next function __cfi_bmi160_core_runtime_resume()

Prevent the UB and improve error handling by returning an error if 'pin'
has an unexpected value.

While at it, simplify the code a bit by moving the 'pin_name' assignment
to the first switch statement.

Fixes: 895bf81e6bbf ("iio:bmi160: add drdy interrupt support")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/a426d669-58bb-4be1-9eaa-6f3d83109e2d@app.fastmail.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 drivers/iio/imu/bmi160/bmi160_core.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/imu/bmi160/bmi160_core.c b/drivers/iio/imu/bmi160/bmi160_core.c
index 5f47708b4c5d..4abb83b75e2e 100644
--- a/drivers/iio/imu/bmi160/bmi160_core.c
+++ b/drivers/iio/imu/bmi160/bmi160_core.c
@@ -573,12 +573,16 @@ static int bmi160_config_pin(struct regmap *regmap, enum bmi160_int_pin pin,
 		int_out_ctrl_shift = BMI160_INT1_OUT_CTRL_SHIFT;
 		int_latch_mask = BMI160_INT1_LATCH_MASK;
 		int_map_mask = BMI160_INT1_MAP_DRDY_EN;
+		pin_name = "INT1";
 		break;
 	case BMI160_PIN_INT2:
 		int_out_ctrl_shift = BMI160_INT2_OUT_CTRL_SHIFT;
 		int_latch_mask = BMI160_INT2_LATCH_MASK;
 		int_map_mask = BMI160_INT2_MAP_DRDY_EN;
+		pin_name = "INT2";
 		break;
+	default:
+		return -EINVAL;
 	}
 	int_out_ctrl_mask = BMI160_INT_OUT_CTRL_MASK << int_out_ctrl_shift;
 
@@ -612,17 +616,8 @@ static int bmi160_config_pin(struct regmap *regmap, enum bmi160_int_pin pin,
 	ret = bmi160_write_conf_reg(regmap, BMI160_REG_INT_MAP,
 				    int_map_mask, int_map_mask,
 				    write_usleep);
-	if (ret) {
-		switch (pin) {
-		case BMI160_PIN_INT1:
-			pin_name = "INT1";
-			break;
-		case BMI160_PIN_INT2:
-			pin_name = "INT2";
-			break;
-		}
+	if (ret)
 		dev_err(dev, "Failed to configure %s IRQ pin", pin_name);
-	}
 
 	return ret;
 }
-- 
2.53.0