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iio: light: Simplify the current to lux LUT 

The look-up-table for currens to lux is simply specifying
all currents from 5..47 mA, if we add some values for 0..5
we can just select the index for the lux value in an array
from the mA value. Use clamp() to get the value in the
range of values in the array.

Cc: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Gregor Riepl <onitake@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Gregor Riepl 2020-02-20 22:20:53 +01:00 committed by Jonathan Cameron
parent 317d4bcca7
commit 070bd30a51
1 changed files with 13 additions and 77 deletions
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90
drivers/iio/light/gp2ap002.c
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@ -205,71 +205,27 @@ err_retrig:
return IRQ_HANDLED; return IRQ_HANDLED;
} }
struct gp2ap002_illuminance {
unsigned int curr;
unsigned int lux;
};
/* /*
* This array maps current and lux. * This array maps current and lux.
* *
* Ambient light sensing range is 3 to 55000 lux. * Ambient light sensing range is 3 to 55000 lux.
* *
* This mapping is based on the following formula. * This mapping is based on the following formula.
* illuminance = 10 ^ (current / 10) * illuminance = 10 ^ (current[mA] / 10)
*
* When the ADC measures 0, return 0 lux.
*/ */
static const struct gp2ap002_illuminance gp2ap002_illuminance_table[] = { static const u16 gp2ap002_illuminance_table[] = {
{ .curr = 5, .lux = 3 }, 0, 1, 1, 2, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 25, 32, 40, 50, 63, 79,
{ .curr = 6, .lux = 4 }, 100, 126, 158, 200, 251, 316, 398, 501, 631, 794, 1000, 1259, 1585,
{ .curr = 7, .lux = 5 }, 1995, 2512, 3162, 3981, 5012, 6310, 7943, 10000, 12589, 15849, 19953,
{ .curr = 8, .lux = 6 }, 25119, 31623, 39811, 50119,
{ .curr = 9, .lux = 8 },
{ .curr = 10, .lux = 10 },
{ .curr = 11, .lux = 12 },
{ .curr = 12, .lux = 16 },
{ .curr = 13, .lux = 20 },
{ .curr = 14, .lux = 25 },
{ .curr = 15, .lux = 32 },
{ .curr = 16, .lux = 40 },
{ .curr = 17, .lux = 50 },
{ .curr = 18, .lux = 63 },
{ .curr = 19, .lux = 79 },
{ .curr = 20, .lux = 100 },
{ .curr = 21, .lux = 126 },
{ .curr = 22, .lux = 158 },
{ .curr = 23, .lux = 200 },
{ .curr = 24, .lux = 251 },
{ .curr = 25, .lux = 316 },
{ .curr = 26, .lux = 398 },
{ .curr = 27, .lux = 501 },
{ .curr = 28, .lux = 631 },
{ .curr = 29, .lux = 794 },
{ .curr = 30, .lux = 1000 },
{ .curr = 31, .lux = 1259 },
{ .curr = 32, .lux = 1585 },
{ .curr = 33, .lux = 1995 },
{ .curr = 34, .lux = 2512 },
{ .curr = 35, .lux = 3162 },
{ .curr = 36, .lux = 3981 },
{ .curr = 37, .lux = 5012 },
{ .curr = 38, .lux = 6310 },
{ .curr = 39, .lux = 7943 },
{ .curr = 40, .lux = 10000 },
{ .curr = 41, .lux = 12589 },
{ .curr = 42, .lux = 15849 },
{ .curr = 43, .lux = 19953 },
{ .curr = 44, .lux = 25119 },
{ .curr = 45, .lux = 31623 },
{ .curr = 46, .lux = 39811 },
{ .curr = 47, .lux = 50119 },
}; };
static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002) static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002)
{ {
const struct gp2ap002_illuminance *ill1;
const struct gp2ap002_illuminance *ill2;
int ret, res; int ret, res;
int i; u16 lux;
ret = iio_read_channel_processed(gp2ap002->alsout, &res); ret = iio_read_channel_processed(gp2ap002->alsout, &res);
if (ret < 0) if (ret < 0)
@ -277,31 +233,11 @@ static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002)
dev_dbg(gp2ap002->dev, "read %d mA from ADC\n", res); dev_dbg(gp2ap002->dev, "read %d mA from ADC\n", res);
ill1 = &gp2ap002_illuminance_table[0]; /* ensure we don't under/overflow */
if (res < ill1->curr) { res = clamp(res, 0, (int)ARRAY_SIZE(gp2ap002_illuminance_table) - 1);
dev_dbg(gp2ap002->dev, "total darkness\n"); lux = gp2ap002_illuminance_table[res];
return 0;
}
for (i = 0; i < ARRAY_SIZE(gp2ap002_illuminance_table) - 1; i++) {
ill1 = &gp2ap002_illuminance_table[i];
ill2 = &gp2ap002_illuminance_table[i + 1];
if (res > ill2->curr) return (int)lux;
continue;
if ((res <= ill1->curr) && (res >= ill2->curr))
break;
}
if (res > ill2->curr) {
dev_info_once(gp2ap002->dev, "max current overflow\n");
return ill2->curr;
}
/* Interpolate and return */
dev_dbg(gp2ap002->dev, "interpolate index %d and %d\n", i, i + 1);
/* How many steps along the curve */
i = res - ill1->curr; /* x - x0 */
/* Linear interpolation */
return ill1->lux + i *
((ill2->lux - ill1->lux) / (ill2->curr - ill1->curr));
} }
static int gp2ap002_read_raw(struct iio_dev *indio_dev, static int gp2ap002_read_raw(struct iio_dev *indio_dev,