On Fri, 26 Oct 2018 23:00:04 -0300
Matheus Tavares <matheus.bernardino@xxxxxx> wrote:
> This patch adds the IIO_CHAN_INFO_SCALE mask to ad2s90_chan and
> implements the relative read behavior at ad2s90_read_raw.
>
> Signed-off-by: Victor Colombo <victorcolombo@xxxxxxxxx>
> Signed-off-by: Matheus Tavares <matheus.bernardino@xxxxxx>
Hi,
A suggestion inline. This is a common case that we have infrastructure
to simplify. + I think your scale factor is very slightly wrong.
Jonathan
> ---
> drivers/staging/iio/resolver/ad2s90.c | 32 ++++++++++++++++++---------
> 1 file changed, 22 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/staging/iio/resolver/ad2s90.c b/drivers/staging/iio/resolver/ad2s90.c
> index b4a6a89c11b0..52b656875ed1 100644
> --- a/drivers/staging/iio/resolver/ad2s90.c
> +++ b/drivers/staging/iio/resolver/ad2s90.c
> @@ -34,19 +34,31 @@ static int ad2s90_read_raw(struct iio_dev *indio_dev,
> int ret;
> struct ad2s90_state *st = iio_priv(indio_dev);
>
> - mutex_lock(&st->lock);
> + switch (m) {
> + case IIO_CHAN_INFO_SCALE:
> + /* 2 * Pi / (2^12 - 1) ~= 0.001534355 */
> + *val = 0;
> + *val2 = 1534355;
Definitely 2^12 - 1? That's a bit unusual if true as it would imply
that 2^12 - 1 and 0 were the same value.
Imagine a smaller version with on 2^2 bits so 0, 1, 2, 3
Values of each are
0, M_PI/2, M_PI, 3*M_PI/2
So the multiplier is 2*M_PI/(2^2) not 2*M_PI/(2^2 - 1)
1/2 vs 2/3 * M_PI
Now this is a very common case so we have the return type
IIO_VAL_FRACTIONAL_LOG2 to give a more obvious and potentially
more accurate representation.
> + return IIO_VAL_INT_PLUS_NANO;
> + case IIO_CHAN_INFO_RAW:
> + mutex_lock(&st->lock);
> +
> + ret = spi_read(st->sdev, st->rx, 2);
> + if (ret < 0) {
> + mutex_unlock(&st->lock);
> + return ret;
> + }
> +
> + *val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
>
> - ret = spi_read(st->sdev, st->rx, 2);
> - if (ret < 0) {
> mutex_unlock(&st->lock);
> - return ret;
> - }
>
> - *val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
> -
> - mutex_unlock(&st->lock);
> + return IIO_VAL_INT;
> + default:
> + break;
> + }
>
> - return IIO_VAL_INT;
> + return -EINVAL;
> }
>
> static const struct iio_info ad2s90_info = {
> @@ -57,7 +69,7 @@ static const struct iio_chan_spec ad2s90_chan = {
> .type = IIO_ANGL,
> .indexed = 1,
> .channel = 0,
> - .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> };
>
> static int ad2s90_probe(struct spi_device *spi)
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