[PATCH] iio: accel: st_accel: Fix invalid mount_matrix on devices without ACPI _ONT method

[Hans de Goede <hdegoede@redhat.com>]

When apply_acpi_orientation() fails, st_accel_common_probe() will fall back
to iio_read_mount_matrix(), which checks for a mount-matrix device property
and if that is not set falls back to the identity matrix.

But when a sensor has no ACPI companion fwnode, or when the ACPI fwnode
does not have a "_ONT" method apply_acpi_orientation() was returning 0,
causing iio_read_mount_matrix() to never get called resulting in an
invalid mount_matrix:

[root@fedora ~]# cat /sys/bus/iio/devices/iio\:device0/mount_matrix
(null), (null), (null); (null), (null), (null); (null), (null), (null)

Fix this by making apply_acpi_orientation() always return an error when
it did not set the mount_matrix.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/iio/accel/st_accel_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/accel/st_accel_core.c b/drivers/iio/accel/st_accel_core.c
index 1628b177d0ed..f7b823ebc96b 100644
--- a/drivers/iio/accel/st_accel_core.c
+++ b/drivers/iio/accel/st_accel_core.c
@@ -1291,12 +1291,12 @@ static int apply_acpi_orientation(struct iio_dev *indio_dev)
 
 	adev = ACPI_COMPANION(indio_dev->dev.parent);
 	if (!adev)
-		return 0;
+		return -ENXIO;
 
 	/* Read _ONT data, which should be a package of 6 integers. */
 	status = acpi_evaluate_object(adev->handle, "_ONT", NULL, &buffer);
 	if (status == AE_NOT_FOUND) {
-		return 0;
+		return -ENXIO;
 	} else if (ACPI_FAILURE(status)) {
 		dev_warn(&indio_dev->dev, "failed to execute _ONT: %d\n",
 			 status);
-- 
2.39.2