On Thu, 20 Feb 2020 22:20:53 +0100
Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> From: Gregor Riepl <onitake@xxxxxxxxx>
>
> 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@xxxxxxx>
> Signed-off-by: Gregor Riepl <onitake@xxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.
Thanks,
Jonathan
> ---
> drivers/iio/light/gp2ap002.c | 92 ++++++------------------------------
> 1 file changed, 14 insertions(+), 78 deletions(-)
>
> diff --git a/drivers/iio/light/gp2ap002.c b/drivers/iio/light/gp2ap002.c
> index f747a42882e0..b24f43f961c8 100644
> --- a/drivers/iio/light/gp2ap002.c
> +++ b/drivers/iio/light/gp2ap002.c
> @@ -204,71 +204,27 @@ static irqreturn_t gp2ap002_prox_irq(int irq, void *d)
> return IRQ_HANDLED;
> }
>
> -struct gp2ap002_illuminance {
> - unsigned int curr;
> - unsigned int lux;
> -};
> -
> /*
> * This array maps current and lux.
> *
> * Ambient light sensing range is 3 to 55000 lux.
> *
> * 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[] = {
> - { .curr = 5, .lux = 3 },
> - { .curr = 6, .lux = 4 },
> - { .curr = 7, .lux = 5 },
> - { .curr = 8, .lux = 6 },
> - { .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 const u16 gp2ap002_illuminance_table[] = {
> + 0, 1, 1, 2, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 25, 32, 40, 50, 63, 79,
> + 100, 126, 158, 200, 251, 316, 398, 501, 631, 794, 1000, 1259, 1585,
> + 1995, 2512, 3162, 3981, 5012, 6310, 7943, 10000, 12589, 15849, 19953,
> + 25119, 31623, 39811, 50119,
> };
>
> static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002)
> {
> - const struct gp2ap002_illuminance *ill1;
> - const struct gp2ap002_illuminance *ill2;
> int ret, res;
> - int i;
> + u16 lux;
>
> ret = iio_read_channel_processed(gp2ap002->alsout, &res);
> if (ret < 0)
> @@ -276,31 +232,11 @@ static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002)
>
> dev_dbg(gp2ap002->dev, "read %d mA from ADC\n", res);
>
> - ill1 = &gp2ap002_illuminance_table[0];
> - if (res < ill1->curr) {
> - dev_dbg(gp2ap002->dev, "total darkness\n");
> - 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)
> - 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));
> + /* ensure we don't under/overflow */
> + res = clamp(res, 0, (int)ARRAY_SIZE(gp2ap002_illuminance_table) - 1);
> + lux = gp2ap002_illuminance_table[res];
> +
> + return (int)lux;
> }
>
> static int gp2ap002_read_raw(struct iio_dev *indio_dev,
