Messages in this thread Patch in this message | | | From | Bryan Freed <> | Subject | [PATCH 2/2] light sensor: Preserve granularity of amplified tsl2583 light sensor values. | Date | Fri, 10 Jun 2011 13:26:20 -0700 |
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Use 64bit lux64 to amplify lux values while preserving granularity. Normalize illuminance_calibbias amplification value at 1024 instead of 1000 so we can avoid 64bit division (div_u64).
Signed-off-by: Bryan Freed <bfreed@chromium.org> --- drivers/staging/iio/light/tsl2583.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/iio/light/tsl2583.c b/drivers/staging/iio/light/tsl2583.c index 5694610..0324ac1 100644 --- a/drivers/staging/iio/light/tsl2583.c +++ b/drivers/staging/iio/light/tsl2583.c @@ -146,7 +146,7 @@ static void taos_defaults(struct tsl2583_chip *chip) chip->taos_settings.als_gain = 0; /* this is actually an index into the gain table */ /* assume clear glass as default */ - chip->taos_settings.als_gain_trim = 1000; + chip->taos_settings.als_gain_trim = 1024; /* default gain trim to account for aperture effects */ chip->taos_settings.als_cal_target = 130; /* Known external ALS reading used for calibration */ @@ -195,6 +195,7 @@ static int taos_get_lux(struct i2c_client *client) { u16 ch0, ch1; /* separated ch0/ch1 data from device */ u32 lux; /* raw lux calculated from device data */ + u64 lux64; u32 ratio; u8 buf[5]; struct taos_lux *p; @@ -298,8 +299,10 @@ static int taos_get_lux(struct i2c_client *client) chip->als_time_scale; /* adjust for active gain scale */ - lux >>= 13; /* tables have factor of 8192 builtin for accuracy */ - lux = (lux * chip->taos_settings.als_gain_trim + 500) / 1000; + lux64 = lux; + lux64 = (lux64 * chip->taos_settings.als_gain_trim + 512) >> 10; + lux64 >>= 13; /* tables have factor of 8192 builtin for accuracy */ + lux = lux64; if (lux > TSL258X_LUX_CALC_OVER_FLOW) { /* check for overflow */ return_max: lux = TSL258X_LUX_CALC_OVER_FLOW; -- 1.7.3.1
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