drivers: sensor: bme280: use int math in decode q31 conv

Fix decoder to use integer math when converting readings to Q31.

Fixes #77295

Signed-off-by: Lauren Murphy <[email protected]>

Author: laurenmurphyx64

drivers/sensor/bosch/bme280/bme280.h

@@ -160,6 +160,17 @@ extern const struct bme280_bus_io bme280_bus_io_i2c;
 					 BME280_TEMP_OVER |  \
 					 BME280_MODE_SLEEP)
 
+/* Convert to Q15.16 */
+#define BME280_TEMP_CONV         100
+#define BME280_TEMP_SHIFT        16
+/* Treat UQ24.8 as Q23.8
+ * Need to divide by 1000 to convert to kPa
+ */
+#define BME280_PRESS_CONV_KPA    1000
+#define BME280_PRESS_SHIFT       23
+/* Treat UQ22.10 as Q21.10 */
+#define BME280_HUM_SHIFT         21
+
 struct bme280_reading {
 	/* Compensated values. */
 	int32_t comp_temp;

drivers/sensor/bosch/bme280/bme280_decoder.c

@@ -54,50 +54,8 @@ static int bme280_decoder_get_size_info(struct sensor_chan_spec chan_spec, size_
 	}
 }
 
-#define BME280_HUM_SHIFT (22)
-#define BME280_PRESS_SHIFT (24)
-#define BME280_TEMP_SHIFT (24)
-
-static void bme280_convert_double_to_q31(double reading, int32_t shift, q31_t *out)
-{
-	reading = reading * pow(2, 31 - shift);
-
-	int64_t reading_round = (reading < 0) ? (reading - 0.5) : (reading + 0.5);
-	int32_t reading_q31 = CLAMP(reading_round, INT32_MIN, INT32_MAX);
-
-	if (reading_q31 < 0) {
-		reading_q31 = abs(reading_q31);
-		reading_q31 = ~reading_q31;
-		reading_q31++;
-	}
-
-	*out = reading_q31;
-}
-
-/* Refer to bme280.c bme280_channel_get() */
-static void bme280_convert_signed_temp_raw_to_q31(int32_t reading, q31_t *out)
-{
-	double temp_double = reading / 100.0;
-
-	bme280_convert_double_to_q31(temp_double, BME280_TEMP_SHIFT, out);
-}
-
-static void bme280_convert_unsigned_pressure_raw_to_q31(uint32_t reading, q31_t *out)
-{
-	double press_double = (reading / 256.0) / 1000.0; /* Pa -> hPa */
-
-	bme280_convert_double_to_q31(press_double, BME280_PRESS_SHIFT, out);
-}
-
-static void bme280_convert_unsigned_humidity_raw_to_q31(uint32_t reading, q31_t *out)
-{
-	double hum_double = (reading / 1024.0);
-
-	bme280_convert_double_to_q31(hum_double, BME280_HUM_SHIFT, out);
-}
-
 static int bme280_decoder_decode(const uint8_t *buffer, struct sensor_chan_spec chan_spec,
-				    uint32_t *fit, uint16_t max_count, void *data_out)
+				 uint32_t *fit, uint16_t max_count, void *data_out)
 {
 	const struct bme280_encoded_data *edata = (const struct bme280_encoded_data *)buffer;
 
@@ -113,26 +71,33 @@ static int bme280_decoder_decode(const uint8_t *buffer, struct sensor_chan_spec
 	switch (chan_spec.chan_type) {
 	case SENSOR_CHAN_AMBIENT_TEMP:
 		if (edata->has_temp) {
-			bme280_convert_signed_temp_raw_to_q31(edata->reading.comp_temp,
-				&out->readings[0].temperature);
+			int32_t readq = edata->reading.comp_temp * pow(2, 31 - BME280_TEMP_SHIFT);
+			int32_t convq = BME280_TEMP_CONV * pow(2, 31 - BME280_TEMP_SHIFT);
+
+			out->readings[0].temperature =
+				(int32_t)((((int64_t)readq) << (31 - BME280_TEMP_SHIFT)) /
+					  ((int64_t)convq));
 			out->shift = BME280_TEMP_SHIFT;
 		} else {
 			return -ENODATA;
 		}
 		break;
 	case SENSOR_CHAN_PRESS:
 		if (edata->has_press) {
-			bme280_convert_unsigned_pressure_raw_to_q31(edata->reading.comp_press,
-				&out->readings[0].pressure);
+			int32_t readq = edata->reading.comp_press;
+			int32_t convq = BME280_PRESS_CONV_KPA * pow(2, 31 - BME280_PRESS_SHIFT);
+
+			out->readings[0].pressure =
+				(int32_t)((((int64_t)readq) << (31 - BME280_PRESS_SHIFT)) /
+					  ((int64_t)convq));
 			out->shift = BME280_PRESS_SHIFT;
 		} else {
 			return -ENODATA;
 		}
 		break;
 	case SENSOR_CHAN_HUMIDITY:
 		if (edata->has_humidity) {
-			bme280_convert_unsigned_humidity_raw_to_q31(edata->reading.comp_humidity,
-				&out->readings[0].humidity);
+			out->readings[0].humidity = edata->reading.comp_humidity;
 			out->shift = BME280_HUM_SHIFT;
 		} else {
 			return -ENODATA;
@@ -147,7 +112,6 @@ static int bme280_decoder_decode(const uint8_t *buffer, struct sensor_chan_spec
 	return 1;
 }
 
-
 SENSOR_DECODER_API_DT_DEFINE() = {
 	.get_frame_count = bme280_decoder_get_frame_count,
 	.get_size_info = bme280_decoder_get_size_info,