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@@ -194,6 +194,7 @@ static int taos_get_lux(struct iio_dev *indio_dev)
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{
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u16 ch0, ch1; /* separated ch0/ch1 data from device */
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u32 lux; /* raw lux calculated from device data */
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+ u64 lux64;
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u32 ratio;
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u8 buf[5];
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struct taos_lux *p;
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@@ -297,9 +298,19 @@ static int taos_get_lux(struct iio_dev *indio_dev)
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lux = (lux + (chip->als_time_scale >> 1)) /
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chip->als_time_scale;
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- /* adjust for active gain scale */
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- lux >>= 13; /* tables have factor of 8192 builtin for accuracy */
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- lux = (lux * chip->taos_settings.als_gain_trim + 500) / 1000;
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+ /* Adjust for active gain scale.
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+ * The taos_device_lux tables above have a factor of 8192 built in,
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+ * so we need to shift right.
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+ * User-specified gain provides a multiplier.
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+ * Apply user-specified gain before shifting right to retain precision.
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+ * Use 64 bits to avoid overflow on multiplication.
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+ * Then go back to 32 bits before division to avoid using div_u64().
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+ */
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+ lux64 = lux;
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+ lux64 = lux64 * chip->taos_settings.als_gain_trim;
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+ lux64 >>= 13;
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+ lux = lux64;
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+ lux = (lux + 500) / 1000;
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if (lux > TSL258X_LUX_CALC_OVER_FLOW) { /* check for overflow */
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return_max:
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lux = TSL258X_LUX_CALC_OVER_FLOW;
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