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iio: isl29018: Support fractional ALS scaling.

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The Industrial IO framework supports scaling ADC values by fractions,
but most drivers default to using whole numbers.
This change turns on fractional scaling in the isl29018 driver.

Signed-off-by: Bryan Freed <bfreed@chromium.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Bryan Freed 2012-09-05 20:55:00 +01:00 committed by Jonathan Cameron
parent 7b123c85bb
commit 932323b74e
1 changed files with 15 additions and 2 deletions
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17
drivers/staging/iio/light/isl29018.c
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@ -63,6 +63,7 @@ struct isl29018_chip {
struct regmap *regmap;
struct mutex lock;
unsigned int lux_scale;
unsigned int lux_uscale;
unsigned int range;
unsigned int adc_bit;
int prox_scheme;
@ -145,13 +146,22 @@ static int isl29018_read_sensor_input(struct isl29018_chip *chip, int mode)
static int isl29018_read_lux(struct isl29018_chip *chip, int *lux)
{
int lux_data;
unsigned int data_x_range, lux_unshifted;
lux_data = isl29018_read_sensor_input(chip, COMMMAND1_OPMODE_ALS_ONCE);
if (lux_data < 0)
return lux_data;
*lux = (lux_data * chip->range * chip->lux_scale) >> chip->adc_bit;
/* To support fractional scaling, separate the unshifted lux
* into two calculations: int scaling and micro-scaling.
* lux_uscale ranges from 0-999999, so about 20 bits. Split
* the /1,000,000 in two to reduce the risk of over/underflow.
*/
data_x_range = lux_data * chip->range;
lux_unshifted = data_x_range * chip->lux_scale;
lux_unshifted += data_x_range / 1000 * chip->lux_uscale / 1000;
*lux = lux_unshifted >> chip->adc_bit;
return 0;
}
@ -339,6 +349,8 @@ static int isl29018_write_raw(struct iio_dev *indio_dev,
mutex_lock(&chip->lock);
if (mask == IIO_CHAN_INFO_CALIBSCALE && chan->type == IIO_LIGHT) {
chip->lux_scale = val;
/* With no write_raw_get_fmt(), val2 is a MICRO fraction. */
chip->lux_uscale = val2;
ret = 0;
}
mutex_unlock(&chip->lock);
@ -379,7 +391,8 @@ static int isl29018_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_CALIBSCALE:
if (chan->type == IIO_LIGHT) {
*val = chip->lux_scale;
ret = IIO_VAL_INT;
*val2 = chip->lux_uscale;
ret = IIO_VAL_INT_PLUS_MICRO;
}
break;
default: