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>
---
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;
--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
