5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mert Seftali [ Upstream commit aa58ecc73466d0cb8c418de98e2225490bf600e3 ] Reading the in_accel_scale attribute on the DMARD09 has always returned -EINVAL: the channels advertise scale via info_mask_shared_by_type so the IIO core exposes the attribute, but dmard09_read_raw() only handles IIO_CHAN_INFO_RAW, so a SCALE read falls through to 'default: return -EINVAL': $ cat .../iio:deviceX/in_accel_scale cat: in_accel_scale: Invalid argument leaving userspace with raw counts it cannot convert to m/s^2. The driver was written from a vendor source [1] without a datasheet, and the scale was declared but never implemented. The vendor source carries the sensitivity: its conversion is acc = raw * GRAVITY_EARTH_1000 / sensitivity (then / 1000 -> m/s^2) with sensitivity = 32 and GRAVITY_EARTH_1000 = 9807 ("about (9.80665)*1000"), i.e. 32 counts correspond to 1 g. That sensitivity applies to the value this driver already reports as raw: the vendor reduces each 16-bit sample to a signed 9-bit value, and the preparation in dmard09_read_raw() yields the same value. It is self-consistent: 256 counts / 32 = 8 g full scale, matching the +/-8g range. Implement the scale derived from that sensitivity using standard gravity: scale = 9.80665 / 32 = 0.3064578125 m/s^2 per LSB Link: https://github.com/minstrelsy/mediatek/blob/1f49d8c87b839651bc89afc870277e8e0f2e2d55/custom/common/kernel/accelerometer/dmard09/dmard09.c [1] Fixes: a4fa6509dda4 ("iio: accel: add support for the Domintech DMARD09 3-axis accelerometer") Signed-off-by: Mert Seftali Reviewed-by: Joshua Crofts Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin --- drivers/iio/accel/dmard09.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/iio/accel/dmard09.c b/drivers/iio/accel/dmard09.c index e6e28c9647776..e2f470d801493 100644 --- a/drivers/iio/accel/dmard09.c +++ b/drivers/iio/accel/dmard09.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #define DMARD09_DRV_NAME "dmard09" @@ -79,6 +80,12 @@ static int dmard09_read_raw(struct iio_dev *indio_dev, *val = accel; return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: + *val = 0; + /* 1 g / 32 LSB, in m/s^2 */ + *val2 = IIO_G_TO_M_S_2(NANO / 32); + + return IIO_VAL_INT_PLUS_NANO; default: return -EINVAL; } -- 2.53.0