Re: [PATCH v3 3/6] iio: pressure: Generalize read_{temp/press/humid}() functions

From: Jonathan Cameron
Date: Sun Mar 24 2024 - 07:36:40 EST

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On Tue, 19 Mar 2024 01:29:22 +0100
Vasileios Amoiridis <vassilisamir@xxxxxxxxx> wrote:

> Add the coefficients for the IIO standard units and the return
> IIO value inside the chip_info structure.
>
> Remove the calculations with the coefficients for the IIO unit
> compatibility from inside the read_{temp/press/humid}() functions
> and move it to the general read_raw() function.
>
> Execute the calculations with the coefficients inside the read_raw()
> oneshot capture function.
>
> In this way, all the data for the calculation of the value are
> located in the chip_info structure of the respective sensor.
>
> Signed-off-by: Vasileios Amoiridis <vassilisamir@xxxxxxxxx>
Hi,

Perhaps it's later in the series, but I still don't much like the hidden nature
of t_fine. I'd much rather that was explicitly 'returned' by the function
- by that I mean read_temp takes an s32 *t_fine and provides that if the pointer
isn't NULL.

Then drop the cached value in bmp280_data which I think just serves to make
this code less readable than it could be.

Then bmp280_compensate_pressure() can take a struct bmp280_calib, s32 adc_press and
s32 t_fine so it just has the data it needs.
Something similar for bmp280_compenstate_temp()

Obviously this is cleaning up stuff that's been there a long time, but
given you are generalizing these functions this seems like the time to
make these other changes.

As it stands, I don't think this code works as t_fine isn't updated
everywhere it needs to be and that is hidden away by it being updated
as a side effect of other calls.

Jonathan

> ---
> drivers/iio/pressure/bmp280-core.c | 189 +++++++++++++++--------------
> drivers/iio/pressure/bmp280.h | 13 +-
> 2 files changed, 106 insertions(+), 96 deletions(-)
>
> diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> index f7a13ff6f26c..6d6173c4b744 100644
> --- a/drivers/iio/pressure/bmp280-core.c
> +++ b/drivers/iio/pressure/bmp280-core.c
> @@ -363,10 +363,9 @@ static u32 bmp280_compensate_press(struct bmp280_data *data,
> return (u32)p;
> }
>
> -static int bmp280_read_temp(struct bmp280_data *data,
> - int *val, int *val2)
> +static int bmp280_read_temp(struct bmp280_data *data, s32 *comp_temp)
> {
> - s32 adc_temp, comp_temp;
> + s32 adc_temp;
> int ret;
>
> ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
> @@ -382,29 +381,20 @@ static int bmp280_read_temp(struct bmp280_data *data,
> dev_err(data->dev, "reading temperature skipped\n");
> return -EIO;
> }
> - comp_temp = bmp280_compensate_temp(data, adc_temp);
>
> - /*
> - * val might be NULL if we're called by the read_press routine,
> - * who only cares about the carry over t_fine value.
> - */
> - if (val) {
> - *val = comp_temp * 10;
> - return IIO_VAL_INT;
> - }
> + if (comp_temp)
> + *comp_temp = bmp280_compensate_temp(data, adc_temp);

As below, I don't think this is updating t_fine.
Another reason to make that update very obvious rather than burried
in this function call.

>
> return 0;
> }
>
> -static int bmp280_read_press(struct bmp280_data *data,
> - int *val, int *val2)
> +static int bmp280_read_press(struct bmp280_data *data, u32 *comp_press)
> {
> - u32 comp_press;
> s32 adc_press;
> int ret;
>
> /* Read and compensate temperature so we get a reading of t_fine. */
> - ret = bmp280_read_temp(data, NULL, NULL);
> + ret = bmp280_read_temp(data, NULL);
> if (ret < 0)
> return ret;
>
> @@ -421,22 +411,19 @@ static int bmp280_read_press(struct bmp280_data *data,
> dev_err(data->dev, "reading pressure skipped\n");
> return -EIO;
> }
> - comp_press = bmp280_compensate_press(data, adc_press);
>
> - *val = comp_press;
> - *val2 = 256000;
> + *comp_press = bmp280_compensate_press(data, adc_press);
>
> - return IIO_VAL_FRACTIONAL;
> + return 0;
> }
>
> -static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
> +static int bmp280_read_humid(struct bmp280_data *data, u32 *comp_humidity)
> {
> - u32 comp_humidity;
> s32 adc_humidity;
> int ret;
>
> /* Read and compensate temperature so we get a reading of t_fine. */
> - ret = bmp280_read_temp(data, NULL, NULL);
> + ret = bmp280_read_temp(data, NULL);
> if (ret < 0)
> return ret;
>
> @@ -453,11 +440,10 @@ static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
> dev_err(data->dev, "reading humidity skipped\n");
> return -EIO;
> }
> - comp_humidity = bmp280_compensate_humidity(data, adc_humidity);
>
> - *val = comp_humidity * 1000 / 1024;
> + *comp_humidity = bmp280_compensate_humidity(data, adc_humidity);
>
> - return IIO_VAL_INT;
> + return 0;
> }
>
> static int bmp280_read_raw_guarded(struct iio_dev *indio_dev,
> @@ -465,6 +451,8 @@ static int bmp280_read_raw_guarded(struct iio_dev *indio_dev,
> int *val, int *val2, long mask)
> {
> struct bmp280_data *data = iio_priv(indio_dev);
> + int chan_value;
> + int ret;
>
> guard(mutex)(&data->lock);
>
> @@ -472,11 +460,29 @@ static int bmp280_read_raw_guarded(struct iio_dev *indio_dev,
> case IIO_CHAN_INFO_PROCESSED:
> switch (chan->type) {
> case IIO_HUMIDITYRELATIVE:
> - return data->chip_info->read_humid(data, val, val2);
> + ret = data->chip_info->read_humid(data, &chan_value);
> + if (ret)
> + return ret;
> +
> + *val = data->chip_info->humid_coeffs[0] * chan_value;
> + *val2 = data->chip_info->humid_coeffs[1];
> + return data->chip_info->humid_coeffs_type;
> case IIO_PRESSURE:
> - return data->chip_info->read_press(data, val, val2);
> + ret = data->chip_info->read_press(data, &chan_value);
> + if (ret)
> + return ret;
> +
> + *val = data->chip_info->press_coeffs[0] * chan_value;
> + *val2 = data->chip_info->press_coeffs[1];
> + return data->chip_info->press_coeffs_type;
> case IIO_TEMP:
> - return data->chip_info->read_temp(data, val, val2);
> + ret = data->chip_info->read_temp(data, &chan_value);
> + if (ret)
> + return ret;
> +
> + *val = data->chip_info->temp_coeffs[0] * chan_value;
> + *val2 = data->chip_info->temp_coeffs[1];
> + return data->chip_info->temp_coeffs_type;
> default:
> return -EINVAL;
> }
> @@ -787,6 +793,8 @@ static int bmp280_chip_config(struct bmp280_data *data)
>
> static const int bmp280_oversampling_avail[] = { 1, 2, 4, 8, 16 };
> static const u8 bmp280_chip_ids[] = { BMP280_CHIP_ID };
> +static const int bmp280_temp_coeffs[] = { 10, 1 };
> +static const int bmp280_press_coeffs[] = { 1, 256000 };
>
> const struct bmp280_chip_info bmp280_chip_info = {
> .id_reg = BMP280_REG_ID,
> @@ -815,6 +823,11 @@ const struct bmp280_chip_info bmp280_chip_info = {
> .num_oversampling_press_avail = ARRAY_SIZE(bmp280_oversampling_avail),
> .oversampling_press_default = BMP280_OSRS_PRESS_16X - 1,
>
> + .temp_coeffs = bmp280_temp_coeffs,
> + .temp_coeffs_type = IIO_VAL_FRACTIONAL,
> + .press_coeffs = bmp280_press_coeffs,
> + .press_coeffs_type = IIO_VAL_FRACTIONAL,
> +
> .chip_config = bmp280_chip_config,
> .read_temp = bmp280_read_temp,
> .read_press = bmp280_read_press,
> @@ -841,6 +854,7 @@ static int bme280_chip_config(struct bmp280_data *data)
> }
>
> static const u8 bme280_chip_ids[] = { BME280_CHIP_ID };
> +static const int bme280_humid_coeffs[] = { 1000, 1024 };
>
> const struct bmp280_chip_info bme280_chip_info = {
> .id_reg = BMP280_REG_ID,
> @@ -863,6 +877,14 @@ const struct bmp280_chip_info bme280_chip_info = {
> .num_oversampling_humid_avail = ARRAY_SIZE(bmp280_oversampling_avail),
> .oversampling_humid_default = BMP280_OSRS_HUMIDITY_16X - 1,
>
> + .temp_coeffs = bmp280_temp_coeffs,
> + .temp_coeffs_type = IIO_VAL_FRACTIONAL,
> + .press_coeffs = bmp280_press_coeffs,
> + .press_coeffs_type = IIO_VAL_FRACTIONAL,
> + .humid_coeffs = bme280_humid_coeffs,
> + .humid_coeffs_type = IIO_VAL_FRACTIONAL,
> +
> +
One blank line is almost always enough.

> .chip_config = bme280_chip_config,
> .read_temp = bmp280_read_temp,
> .read_press = bmp280_read_press,
> @@ -988,9 +1010,8 @@ static u32 bmp380_compensate_press(struct bmp280_data *data, u32 adc_press)
> return comp_press;
> }
>
> -static int bmp380_read_temp(struct bmp280_data *data, int *val, int *val2)
> +static int bmp380_read_temp(struct bmp280_data *data, s32 *comp_temp)
> {
> - s32 comp_temp;
> u32 adc_temp;
> int ret;
>
> @@ -1006,29 +1027,20 @@ static int bmp380_read_temp(struct bmp280_data *data, int *val, int *val2)
> dev_err(data->dev, "reading temperature skipped\n");
> return -EIO;
> }
> - comp_temp = bmp380_compensate_temp(data, adc_temp);
>
> - /*
> - * Val might be NULL if we're called by the read_press routine,
> - * who only cares about the carry over t_fine value.
> - */
> - if (val) {
> - /* IIO reports temperatures in milli Celsius */
> - *val = comp_temp * 10;
> - return IIO_VAL_INT;
> - }
> + if (comp_temp)
> + *comp_temp = bmp380_compensate_temp(data, adc_temp);
>

I'm confused. If comp_temp is not provided then t_fine isn't updated
so this function isn't doing anything?

> return 0;
> }
>
> -static int bmp380_read_press(struct bmp280_data *data, int *val, int *val2)
> +static int bmp380_read_press(struct bmp280_data *data, u32 *comp_press)
> {
> - s32 comp_press;
> u32 adc_press;
> int ret;
>
> /* Read and compensate for temperature so we get a reading of t_fine */

As above, I don't think it does.

> - ret = bmp380_read_temp(data, NULL, NULL);
> + ret = bmp380_read_temp(data, NULL);
> if (ret)
> return ret;
>
> @@ -1044,13 +1056,10 @@ static int bmp380_read_press(struct bmp280_data *data, int *val, int *val2)
> dev_err(data->dev, "reading pressure skipped\n");
> return -EIO;
> }
> - comp_press = bmp380_compensate_press(data, adc_press);
>
> - *val = comp_press;
> - /* Compensated pressure is in cPa (centipascals) */
> - *val2 = 100000;
> + *comp_press = bmp380_compensate_press(data, adc_press);
>
> - return IIO_VAL_FRACTIONAL;
> + return 0;
> }
>

J

Next message: Russell King (Oracle): "Re: [PATCH 0/3] Fix EEE support for MT7531 and MT7988 SoC switch"
Previous message: Andy Yan: "[PATCH] arm64: dts: rockchip: Fix the i2c address of es8316 on Cool Pi CM5"
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