On 20/11/14 12:00, Vlad Dogaru wrote:
> This version of the code avoids extra memory copy operations and is
> somewhat smaller in code size.
>
> Signed-off-by: Vlad Dogaru <vlad.dogaru@xxxxxxxxx>
Thanks for doing this - I'm happy with the result, but would like to
let Hartmut have a few days to take a look if he wants to so will
let it sit on the list for now.
Thanks,
Jonathan
> ---
> drivers/iio/pressure/bmp280.c | 140 ++++++++++++++++--------------------------
> 1 file changed, 52 insertions(+), 88 deletions(-)
>
> diff --git a/drivers/iio/pressure/bmp280.c b/drivers/iio/pressure/bmp280.c
> index 75038da..47dfd34 100644
> --- a/drivers/iio/pressure/bmp280.c
> +++ b/drivers/iio/pressure/bmp280.c
> @@ -80,16 +80,12 @@ struct bmp280_data {
> s32 t_fine;
> };
>
> -/* Compensation parameters. */
> -struct bmp280_comp_temp {
> - u16 dig_t1;
> - s16 dig_t2, dig_t3;
> -};
> -
> -struct bmp280_comp_press {
> - u16 dig_p1;
> - s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_p9;
> -};
> +/*
> + * These enums are used for indexing into the array of compensation
> + * parameters.
> + */
> +enum { T1, T2, T3 };
> +enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };
>
> static const struct iio_chan_spec bmp280_channels[] = {
> {
> @@ -141,54 +137,6 @@ static const struct regmap_config bmp280_regmap_config = {
> .volatile_reg = bmp280_is_volatile_reg,
> };
>
> -static int bmp280_read_compensation_temp(struct bmp280_data *data,
> - struct bmp280_comp_temp *comp)
> -{
> - int ret;
> - __le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];
> -
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
> - buf, BMP280_COMP_TEMP_REG_COUNT);
> - if (ret < 0) {
> - dev_err(&data->client->dev,
> - "failed to read temperature calibration parameters\n");
> - return ret;
> - }
> -
> - comp->dig_t1 = (u16) le16_to_cpu(buf[0]);
> - comp->dig_t2 = (s16) le16_to_cpu(buf[1]);
> - comp->dig_t3 = (s16) le16_to_cpu(buf[2]);
> -
> - return 0;
> -}
> -
> -static int bmp280_read_compensation_press(struct bmp280_data *data,
> - struct bmp280_comp_press *comp)
> -{
> - int ret;
> - __le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
> -
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
> - buf, BMP280_COMP_PRESS_REG_COUNT);
> - if (ret < 0) {
> - dev_err(&data->client->dev,
> - "failed to read pressure calibration parameters\n");
> - return ret;
> - }
> -
> - comp->dig_p1 = (u16) le16_to_cpu(buf[0]);
> - comp->dig_p2 = (s16) le16_to_cpu(buf[1]);
> - comp->dig_p3 = (s16) le16_to_cpu(buf[2]);
> - comp->dig_p4 = (s16) le16_to_cpu(buf[3]);
> - comp->dig_p5 = (s16) le16_to_cpu(buf[4]);
> - comp->dig_p6 = (s16) le16_to_cpu(buf[5]);
> - comp->dig_p7 = (s16) le16_to_cpu(buf[6]);
> - comp->dig_p8 = (s16) le16_to_cpu(buf[7]);
> - comp->dig_p9 = (s16) le16_to_cpu(buf[8]);
> -
> - return 0;
> -}
> -
> /*
> * Returns temperature in DegC, resolution is 0.01 DegC. Output value of
> * "5123" equals 51.23 DegC. t_fine carries fine temperature as global
> @@ -197,16 +145,33 @@ static int bmp280_read_compensation_press(struct bmp280_data *data,
> * Taken from datasheet, Section 3.11.3, "Compensation formula".
> */
> static s32 bmp280_compensate_temp(struct bmp280_data *data,
> - struct bmp280_comp_temp *comp,
> s32 adc_temp)
> {
> + int ret;
> s32 var1, var2, t;
> + __le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];
> +
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
> + buf, BMP280_COMP_TEMP_REG_COUNT);
> + if (ret < 0) {
> + dev_err(&data->client->dev,
> + "failed to read temperature calibration parameters\n");
> + return ret;
> + }
>
> - var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *
> - ((s32) comp->dig_t2)) >> 11;
> - var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *
> - ((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *
> - ((s32) comp->dig_t3)) >> 14;
> + /*
> + * The double casts are necessary because le16_to_cpu returns an
> + * unsigned 16-bit value. Casting that value directly to a
> + * signed 32-bit will not do proper sign extension.
> + *
> + * Conversely, T1 and P1 are unsigned values, so they can be
> + * cast straight to the larger type.
> + */
> + var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *
> + ((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;
> + var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *
> + ((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *
> + ((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;
>
> data->t_fine = var1 + var2;
> t = (data->t_fine * 5 + 128) >> 8;
> @@ -222,27 +187,36 @@ static s32 bmp280_compensate_temp(struct bmp280_data *data,
> * Taken from datasheet, Section 3.11.3, "Compensation formula".
> */
> static u32 bmp280_compensate_press(struct bmp280_data *data,
> - struct bmp280_comp_press *comp,
> s32 adc_press)
> {
> + int ret;
> s64 var1, var2, p;
> + __le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
> +
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
> + buf, BMP280_COMP_PRESS_REG_COUNT);
> + if (ret < 0) {
> + dev_err(&data->client->dev,
> + "failed to read pressure calibration parameters\n");
> + return ret;
> + }
>
> - var1 = ((s64) data->t_fine) - 128000;
> - var2 = var1 * var1 * (s64) comp->dig_p6;
> - var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);
> - var2 = var2 + (((s64) comp->dig_p4) << 35);
> - var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +
> - ((var1 * (s64) comp->dig_p2) << 12);
> - var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;
> + var1 = ((s64)data->t_fine) - 128000;
> + var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);
> + var2 = var2 + ((var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17);
> + var2 = var2 + (((s64)(s16)le16_to_cpu(buf[P4])) << 35);
> + var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +
> + ((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);
> + var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;
>
> if (var1 == 0)
> return 0;
>
> - p = ((((s64) 1048576 - adc_press) << 31) - var2) * 3125;
> + p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
> p = div64_s64(p, var1);
> - var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;
> - var2 = (((s64) comp->dig_p8) * p) >> 19;
> - p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_p7) << 4);
> + var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;
> + var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;
> + p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);
>
> return (u32) p;
> }
> @@ -253,11 +227,6 @@ static int bmp280_read_temp(struct bmp280_data *data,
> int ret;
> __be32 tmp = 0;
> s32 adc_temp, comp_temp;
> - struct bmp280_comp_temp comp;
> -
> - ret = bmp280_read_compensation_temp(data, &comp);
> - if (ret < 0)
> - return ret;
>
> ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
> (u8 *) &tmp, 3);
> @@ -267,7 +236,7 @@ static int bmp280_read_temp(struct bmp280_data *data,
> }
>
> adc_temp = be32_to_cpu(tmp) >> 12;
> - comp_temp = bmp280_compensate_temp(data, &comp, adc_temp);
> + comp_temp = bmp280_compensate_temp(data, adc_temp);
>
> /*
> * val might be NULL if we're called by the read_press routine,
> @@ -288,11 +257,6 @@ static int bmp280_read_press(struct bmp280_data *data,
> __be32 tmp = 0;
> s32 adc_press;
> u32 comp_press;
> - struct bmp280_comp_press comp;
> -
> - ret = bmp280_read_compensation_press(data, &comp);
> - if (ret < 0)
> - return ret;
>
> /* Read and compensate temperature so we get a reading of t_fine. */
> ret = bmp280_read_temp(data, NULL);
> @@ -307,7 +271,7 @@ static int bmp280_read_press(struct bmp280_data *data,
> }
>
> adc_press = be32_to_cpu(tmp) >> 12;
> - comp_press = bmp280_compensate_press(data, &comp, adc_press);
> + comp_press = bmp280_compensate_press(data, adc_press);
>
> *val = comp_press;
> *val2 = 256000;
>
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