[PATCH v4 3/4] iio: accel: adxl345: Implement event scaling for ABI compliance

[Taha Ed-Dafili <0rayn.dev@gmail.com>]

The ADXL345 uses a fixed threshold resolution of 62.5 mg/LSB for
event-related registers. Previously, the driver reported raw
values without a scale factor.

Implement IIO_EV_INFO_SCALE for all event types to provide the
conversion factor (0.612915 m/s^2) as required by the IIO ABI.

Consequently, remove the obsolete comment in adxl345_read_event_value()
which stated that the scale factor is not applied.

Add explicit write rejection for IIO_EV_INFO_SCALE in
adxl345_write_event_value() returning -EINVAL.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Taha Ed-Dafili <0rayn.dev@gmail.com>
---
 drivers/iio/accel/adxl345_core.c | 37 ++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 78e3f799ecc1..eac4ab052fa2 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -213,7 +213,8 @@ static const struct iio_event_spec adxl345_events[] = {
 		.dir = IIO_EV_DIR_RISING,
 		.mask_shared_by_type =
 			BIT(IIO_EV_INFO_ENABLE) |
-			BIT(IIO_EV_INFO_VALUE),
+			BIT(IIO_EV_INFO_VALUE)	|
+			BIT(IIO_EV_INFO_SCALE),
 	},
 	{
 		/* activity, ac bit set */
@@ -221,22 +222,27 @@ static const struct iio_event_spec adxl345_events[] = {
 		.dir = IIO_EV_DIR_RISING,
 		.mask_shared_by_type =
 			BIT(IIO_EV_INFO_ENABLE) |
-			BIT(IIO_EV_INFO_VALUE),
+			BIT(IIO_EV_INFO_VALUE)	|
+			BIT(IIO_EV_INFO_SCALE),
 	},
 	{
 		/* single tap */
 		.type = IIO_EV_TYPE_GESTURE,
 		.dir = IIO_EV_DIR_SINGLETAP,
 		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
-		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
+		.mask_shared_by_type =
+			BIT(IIO_EV_INFO_VALUE)	|
+			BIT(IIO_EV_INFO_SCALE)	|
 			BIT(IIO_EV_INFO_TIMEOUT),
 	},
 	{
 		/* double tap */
 		.type = IIO_EV_TYPE_GESTURE,
 		.dir = IIO_EV_DIR_DOUBLETAP,
-		.mask_shared_by_type = BIT(IIO_EV_INFO_ENABLE) |
-			BIT(IIO_EV_INFO_RESET_TIMEOUT) |
+		.mask_shared_by_type =
+			BIT(IIO_EV_INFO_ENABLE)		|
+			BIT(IIO_EV_INFO_SCALE)		|
+			BIT(IIO_EV_INFO_RESET_TIMEOUT)  |
 			BIT(IIO_EV_INFO_TAP2_MIN_DELAY),
 	},
 };
@@ -275,6 +281,7 @@ static const struct iio_event_spec adxl345_fake_chan_events[] = {
 		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
 		.mask_shared_by_type =
 			BIT(IIO_EV_INFO_VALUE) |
+			BIT(IIO_EV_INFO_SCALE) |
 			BIT(IIO_EV_INFO_PERIOD),
 	},
 	{
@@ -284,6 +291,7 @@ static const struct iio_event_spec adxl345_fake_chan_events[] = {
 		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
 		.mask_shared_by_type =
 			BIT(IIO_EV_INFO_VALUE) |
+			BIT(IIO_EV_INFO_SCALE) |
 			BIT(IIO_EV_INFO_PERIOD),
 	},
 };
@@ -1341,6 +1349,16 @@ static int adxl345_read_event_value(struct iio_dev *indio_dev,
 	unsigned int tap_threshold;
 	int ret;
 
+	/*
+	 * The event threshold LSB is fixed at 62.5 mg/LSB
+	 * 0.0625 * 9.80665 = 0.612915625 m/s^2
+	 */
+	if (info == IIO_EV_INFO_SCALE) {
+		*val = 0;
+		*val2 = 612915;
+		return IIO_VAL_INT_PLUS_MICRO;
+	}
+
 	switch (type) {
 	case IIO_EV_TYPE_MAG:
 		return adxl345_read_mag_value(st, dir, info,
@@ -1355,12 +1373,6 @@ static int adxl345_read_event_value(struct iio_dev *indio_dev,
 	case IIO_EV_TYPE_GESTURE:
 		switch (info) {
 		case IIO_EV_INFO_VALUE:
-			/*
-			 * The scale factor would be 62.5mg/LSB (i.e. 0xFF = 16g) but
-			 * not applied here. In context of this general purpose sensor,
-			 * what imports is rather signal intensity than the absolute
-			 * measured g value.
-			 */
 			ret = regmap_read(st->regmap, ADXL345_REG_THRESH_TAP,
 					  &tap_threshold);
 			if (ret)
@@ -1401,6 +1413,9 @@ static int adxl345_write_event_value(struct iio_dev *indio_dev,
 	if (ret)
 		return ret;
 
+	if (info == IIO_EV_INFO_SCALE)
+		return -EINVAL;
+
 	switch (type) {
 	case IIO_EV_TYPE_MAG:
 		ret = adxl345_write_mag_value(st, dir, info,
-- 
2.47.3