On 11/15/2011 04:30 PM, Lars-Peter Clausen wrote:
> We basically use the same for formating the DACs scale in almost all DAC
> drivers. So put this into a common helper function which does the job for us.
> The helper function uses 64-bit math to be as accurate as possible to minimize
> the error we get when multiplying out_voltage_scale with out_voltage_raw.
>
Nice idea.
As stated below, I do wonder if this isn't more general than dacs and
perhaps needs a more descriptive name?
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
> drivers/staging/iio/dac/ad5064.c | 15 ++++++---------
> drivers/staging/iio/dac/ad5360.c | 15 ++++++---------
> drivers/staging/iio/dac/ad5446.c | 7 +------
> drivers/staging/iio/dac/ad5504.c | 7 +------
> drivers/staging/iio/dac/ad5624r_spi.c | 7 +------
> drivers/staging/iio/dac/ad5686.c | 8 +-------
> drivers/staging/iio/dac/ad5791.c | 4 +---
> drivers/staging/iio/dac/dac.h | 24 ++++++++++++++++++++++++
> 8 files changed, 41 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/staging/iio/dac/ad5064.c b/drivers/staging/iio/dac/ad5064.c
> index 867e4ab..a3ffb4f 100644
> --- a/drivers/staging/iio/dac/ad5064.c
> +++ b/drivers/staging/iio/dac/ad5064.c
> @@ -281,7 +281,7 @@ static int ad5064_read_raw(struct iio_dev *indio_dev,
> {
> struct ad5064_state *st = iio_priv(indio_dev);
> unsigned int vref;
> - int scale_uv;
> + int vref_uv;
>
> switch (m) {
> case 0:
> @@ -289,14 +289,11 @@ static int ad5064_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> vref = st->chip_info->shared_vref ? 0 : chan->channel;
> - scale_uv = regulator_get_voltage(st->vref_reg[vref].consumer);
> - if (scale_uv < 0)
> - return scale_uv;
> -
> - scale_uv = (scale_uv * 100) >> chan->scan_type.realbits;
> - *val = scale_uv / 100000;
> - *val2 = (scale_uv % 100000) * 10;
> - return IIO_VAL_INT_PLUS_MICRO;
> + vref_uv = regulator_get_voltage(st->vref_reg[vref].consumer);
> + if (vref_uv < 0)
> + return vref_uv;
> +
> + return iio_dac_format_scale(vref_uv, chan, val, val2);
> default:
> break;
> }
> diff --git a/drivers/staging/iio/dac/ad5360.c b/drivers/staging/iio/dac/ad5360.c
> index 012d714..8fbd68b 100644
> --- a/drivers/staging/iio/dac/ad5360.c
> +++ b/drivers/staging/iio/dac/ad5360.c
> @@ -372,7 +372,7 @@ static int ad5360_read_raw(struct iio_dev *indio_dev,
> {
> struct ad5360_state *st = iio_priv(indio_dev);
> unsigned int ofs_index;
> - int scale_uv;
> + int vref_uv;
> int ret;
>
> switch (m) {
> @@ -385,14 +385,11 @@ static int ad5360_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> /* vout = 4 * vref * dac_code */
> - scale_uv = ad5360_get_channel_vref(st, chan->channel) * 4 * 100;
> - if (scale_uv < 0)
> - return scale_uv;
> -
> - scale_uv >>= (chan->scan_type.realbits);
> - *val = scale_uv / 100000;
> - *val2 = (scale_uv % 100000) * 10;
> - return IIO_VAL_INT_PLUS_MICRO;
> + vref_uv = ad5360_get_channel_vref(st, chan->channel) * 4 * 100;
> + if (vref_uv < 0)
> + return vref_uv;
> +
> + return iio_dac_format_scale(vref_uv, chan, val, val2);
> case IIO_CHAN_INFO_CALIBBIAS:
> ret = ad5360_read(indio_dev, AD5360_READBACK_OFFSET,
> chan->address);
> diff --git a/drivers/staging/iio/dac/ad5446.c b/drivers/staging/iio/dac/ad5446.c
> index ef1ad11..6b0fe7f 100644
> --- a/drivers/staging/iio/dac/ad5446.c
> +++ b/drivers/staging/iio/dac/ad5446.c
> @@ -278,15 +278,10 @@ static int ad5446_read_raw(struct iio_dev *indio_dev,
> long m)
> {
> struct ad5446_state *st = iio_priv(indio_dev);
> - unsigned long scale_uv;
>
> switch (m) {
> case IIO_CHAN_INFO_SCALE:
> - scale_uv = (st->vref_mv * 1000) >> chan->scan_type.realbits;
> - *val = scale_uv / 1000;
> - *val2 = (scale_uv % 1000) * 1000;
> - return IIO_VAL_INT_PLUS_MICRO;
> -
> + return iio_dac_format_scale(st->vref_mv * 1000, chan, val, val2);
> }
> return -EINVAL;
> }
> diff --git a/drivers/staging/iio/dac/ad5504.c b/drivers/staging/iio/dac/ad5504.c
> index f20a5dc..7021e83 100644
> --- a/drivers/staging/iio/dac/ad5504.c
> +++ b/drivers/staging/iio/dac/ad5504.c
> @@ -77,7 +77,6 @@ static int ad5504_read_raw(struct iio_dev *indio_dev,
> long m)
> {
> struct ad5504_state *st = iio_priv(indio_dev);
> - unsigned long scale_uv;
> int ret;
>
> switch (m) {
> @@ -90,11 +89,7 @@ static int ad5504_read_raw(struct iio_dev *indio_dev,
>
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> - scale_uv = (st->vref_mv * 1000) >> chan->scan_type.realbits;
> - *val = scale_uv / 1000;
> - *val2 = (scale_uv % 1000) * 1000;
> - return IIO_VAL_INT_PLUS_MICRO;
> -
> + return iio_dac_format_scale(st->vref_mv * 1000, chan, val, val2);
> }
> return -EINVAL;
> }
> diff --git a/drivers/staging/iio/dac/ad5624r_spi.c b/drivers/staging/iio/dac/ad5624r_spi.c
> index 6cb00e1..76d6a34 100644
> --- a/drivers/staging/iio/dac/ad5624r_spi.c
> +++ b/drivers/staging/iio/dac/ad5624r_spi.c
> @@ -99,15 +99,10 @@ static int ad5624r_read_raw(struct iio_dev *indio_dev,
> long m)
> {
> struct ad5624r_state *st = iio_priv(indio_dev);
> - unsigned long scale_uv;
>
> switch (m) {
> case IIO_CHAN_INFO_SCALE:
> - scale_uv = (st->vref_mv * 1000) >> chan->scan_type.realbits;
> - *val = scale_uv / 1000;
> - *val2 = (scale_uv % 1000) * 1000;
> - return IIO_VAL_INT_PLUS_MICRO;
> -
> + return iio_dac_format_scale(st->vref_mv * 1000, chan, val, val2);
> }
> return -EINVAL;
> }
> diff --git a/drivers/staging/iio/dac/ad5686.c b/drivers/staging/iio/dac/ad5686.c
> index bbaa928..845f79d 100644
> --- a/drivers/staging/iio/dac/ad5686.c
> +++ b/drivers/staging/iio/dac/ad5686.c
> @@ -293,7 +293,6 @@ static int ad5686_read_raw(struct iio_dev *indio_dev,
> long m)
> {
> struct ad5686_state *st = iio_priv(indio_dev);
> - unsigned long scale_uv;
> int ret;
>
> switch (m) {
> @@ -307,12 +306,7 @@ static int ad5686_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
> break;
> case IIO_CHAN_INFO_SCALE:
> - scale_uv = (st->vref_mv * 100000)
> - >> (chan->scan_type.realbits);
> - *val = scale_uv / 100000;
> - *val2 = (scale_uv % 100000) * 10;
> - return IIO_VAL_INT_PLUS_MICRO;
> -
> + return iio_dac_format_scale(st->vref_mv * 1000, chan, val, val2);
> }
> return -EINVAL;
> }
> diff --git a/drivers/staging/iio/dac/ad5791.c b/drivers/staging/iio/dac/ad5791.c
> index 79c4821..462c423 100644
> --- a/drivers/staging/iio/dac/ad5791.c
> +++ b/drivers/staging/iio/dac/ad5791.c
> @@ -238,9 +238,7 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
> *val >>= chan->scan_type.shift;
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> - *val = 0;
> - *val2 = (((u64)st->vref_mv) * 1000000ULL) >> chan->scan_type.realbits;
> - return IIO_VAL_INT_PLUS_MICRO;
> + return iio_dac_format_scale(st->vref_mv * 1000, chan, val, val2);
> case IIO_CHAN_INFO_OFFSET:
> val64 = (((u64)st->vref_neg_mv) << chan->scan_type.realbits);
> do_div(val64, st->vref_mv);
> diff --git a/drivers/staging/iio/dac/dac.h b/drivers/staging/iio/dac/dac.h
> index 0754d71..ad43e2f 100644
> --- a/drivers/staging/iio/dac/dac.h
> +++ b/drivers/staging/iio/dac/dac.h
> @@ -2,5 +2,29 @@
> * dac.h - sysfs attributes associated with DACs
> */
>
> +#include <linux/math64.h>
> +
> #define IIO_DEV_ATTR_OUT_RAW(_num, _store, _addr) \
> IIO_DEVICE_ATTR(out_voltage##_num##_raw, S_IWUSR, NULL, _store, _addr)
> +
This is actually pretty similar to that used for some adc's as well.
Maybe it wants a less dac focused and more descriptive name?
> +/* iio_dac_format_scale: Helper function for formating the scale attribute for a
> + * DAC.
kernel doc formatting please. Close, but few minor differences..
> + *
> + * @vref_span_uv: span of the reference voltage in microvolts
> + * @chan: channel to format for
> + * @val: val of iio raw_write callback
> + * @val2: val2 of the iio raw_write callback
> + */
> +static inline int iio_dac_format_scale(unsigned long vref_span_uv,
> + const struct iio_chan_spec *chan, unsigned int *val, unsigned int *val2)
> +{
> + u64 result;
> + u32 _val2;
> +
> + result = (((u64)vref_span_uv) * 1000) >> chan->scan_type.realbits;
> +
> + *val = div_u64_rem(result, 1000000, &_val2);
> + *val2 = _val2;
> +
> + return IIO_VAL_INT_PLUS_MICRO;
> +}
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