[PATCH v4 1/4] iio: cros_ec: Add sign vector in core for backward compatibility

[Gwendal Grignou]

To allow cros_ec iio core library to be used with legacy device, add a
vector to rotate sensor data if necessary: legacy devices are not
reporting data in HTML5/Android sensor referential.

Check the data is not rotated on recent chromebooks that use the HTML5
standard to present sensor data.

Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
 drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c | 4 ++++
 include/linux/iio/common/cros_ec_sensors_core.h           | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
index 719a0df5aeeb..e8a4d78659c8 100644
--- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
+++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
@@ -66,6 +66,9 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
 		}
 		state->type = state->resp->info.type;
 		state->loc = state->resp->info.location;
+
+		/* Set sign vector, only used for backward compatibility. */
+		memset(state->sign, 1, CROS_EC_SENSOR_MAX_AXIS);
 	}
 
 	return 0;
@@ -254,6 +257,7 @@ static int cros_ec_sensors_read_data_unsafe(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
+		*data *= st->sign[i];
 		data++;
 	}
 
diff --git a/include/linux/iio/common/cros_ec_sensors_core.h b/include/linux/iio/common/cros_ec_sensors_core.h
index ce16445411ac..a1c85ad4df91 100644
--- a/include/linux/iio/common/cros_ec_sensors_core.h
+++ b/include/linux/iio/common/cros_ec_sensors_core.h
@@ -71,6 +71,7 @@ struct cros_ec_sensors_core_state {
 	enum motionsensor_location loc;
 
 	s16 calib[CROS_EC_SENSOR_MAX_AXIS];
+	s8 sign[CROS_EC_SENSOR_MAX_AXIS];
 
 	u8 samples[CROS_EC_SAMPLE_SIZE];
 
-- 
2.22.0.410.gd8fdbe21b5-goog