On 10/19/11 13:23, Lars-Peter Clausen wrote:
> The ad5791 currently assumes that the negative and positive supply have the
> same absolute value, which is not necessarily true. This patch introduces a
> offset attribute which will contain the negative supply voltage scaled
> according to the iio spec. The raw attribute now accepts values in the range
> of 0 to max instead of -max/2 to max/2.
>
> While we are at it also fix the vref span calculation. Since both positive and
> negative reference voltages are specificed as absolute values we need to add
> them and not subtract them to get the reference voltage span.
Everything commented here is fine, but one odd looking removal...
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
> drivers/staging/iio/dac/ad5791.c | 24 ++++++++++++++++--------
> drivers/staging/iio/dac/ad5791.h | 2 ++
> 2 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/staging/iio/dac/ad5791.c b/drivers/staging/iio/dac/ad5791.c
> index 9a76c43..c465fcf 100644
> --- a/drivers/staging/iio/dac/ad5791.c
> +++ b/drivers/staging/iio/dac/ad5791.c
> @@ -77,7 +77,8 @@ static int ad5791_spi_read(struct spi_device *spi, u8 addr, u32 *val)
> .indexed = 1, \
> .address = AD5791_ADDR_DAC0, \
> .channel = 0, \
> - .info_mask = (1 << IIO_CHAN_INFO_SCALE_SHARED), \
> + .info_mask = (1 << IIO_CHAN_INFO_SCALE_SHARED) | \
> + (1 << IIO_CHAN_INFO_OFFSET_SHARED), \
> .scan_type = IIO_ST('u', bits, 24, shift) \
> }
>
> @@ -225,6 +226,7 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
> long m)
> {
> struct ad5791_state *st = iio_priv(indio_dev);
> + u64 val64;
> int ret;
>
> switch (m) {
> @@ -234,12 +236,16 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
> return ret;
> *val &= AD5791_DAC_MASK;
> *val >>= chan->scan_type.shift;
> - *val -= (1 << (chan->scan_type.realbits - 1));
> return IIO_VAL_INT;
> case (1 << IIO_CHAN_INFO_SCALE_SHARED):
> *val = 0;
> *val2 = (st->vref_mv * 1000) >> chan->scan_type.realbits;
> return IIO_VAL_INT_PLUS_MICRO;
> + case (1 << IIO_CHAN_INFO_OFFSET_SHARED):
> + val64 = (((u64)st->vref_neg_mv) << chan->scan_type.realbits);
> + do_div(val64, st->vref_mv);
> + *val = -val64;
> + return IIO_VAL_INT;
> default:
> return -EINVAL;
> }
> @@ -257,7 +263,6 @@ static int ad5791_write_raw(struct iio_dev *indio_dev,
>
> switch (mask) {
> case 0:
> - val += (1 << (chan->scan_type.realbits - 1));
This line looks suspicious. What is it doing in this patch?
I'll be honest and say I'm not sure why it was there in the first place, but
I can't immediately see what it has to do with the rest of the patch.
> val &= AD5791_RES_MASK(chan->scan_type.realbits);
> val <<= chan->scan_type.shift;
>
> @@ -309,12 +314,15 @@ static int __devinit ad5791_probe(struct spi_device *spi)
> st->pwr_down = true;
> st->spi = spi;
>
> - if (!IS_ERR(st->reg_vss) && !IS_ERR(st->reg_vdd))
> - st->vref_mv = (pos_voltage_uv - neg_voltage_uv) / 1000;
> - else if (pdata)
> - st->vref_mv = pdata->vref_pos_mv - pdata->vref_neg_mv;
> - else
> + if (!IS_ERR(st->reg_vss) && !IS_ERR(st->reg_vdd)) {
> + st->vref_mv = (pos_voltage_uv + neg_voltage_uv) / 1000;
> + st->vref_neg_mv = neg_voltage_uv / 1000;
> + } else if (pdata) {
> + st->vref_mv = pdata->vref_pos_mv + pdata->vref_neg_mv;
> + st->vref_neg_mv = pdata->vref_neg_mv;
> + } else {
> dev_warn(&spi->dev, "reference voltage unspecified\n");
> + }
>
> ret = ad5791_spi_write(spi, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
> if (ret)
> diff --git a/drivers/staging/iio/dac/ad5791.h b/drivers/staging/iio/dac/ad5791.h
> index 2a50a11..fd7edbd 100644
> --- a/drivers/staging/iio/dac/ad5791.h
> +++ b/drivers/staging/iio/dac/ad5791.h
> @@ -82,6 +82,7 @@ struct ad5791_chip_info {
> * @reg_vss: negative supply regulator
> * @chip_info: chip model specific constants
> * @vref_mv: actual reference voltage used
> + * @vref_neg_mv: voltage of the negative supply
> * @pwr_down_mode current power down mode
> */
>
> @@ -91,6 +92,7 @@ struct ad5791_state {
> struct regulator *reg_vss;
> const struct ad5791_chip_info *chip_info;
> unsigned short vref_mv;
> + unsigned int vref_neg_mv;
> unsigned ctrl;
> unsigned pwr_down_mode;
> bool pwr_down;
--
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