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SubjectRe: [PATCH 2/4] iio: hi8435: avoid garbage event at first enable
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On 19/05/17 15:48, Nikita Yushchenko wrote:
> Currently, driver generates events for channels if new reading differs
> from previous one. This "previous value" is initialized to zero, which
> results into event if value is constant-one.
>
> Fix that by initializing "previous value" by reading at event enable
> time.
>
> This provides reliable sequence for userspace:
> - enable event,
> - AFTER THAT read current value,
> - AFTER THAT each event will correspond to change.
>
> Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
I'm hoping there aren't any userspace apps out there relying on this
'unusual' behaviour. *cross fingers*

Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan
> ---
> drivers/iio/adc/hi8435.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/hi8435.c b/drivers/iio/adc/hi8435.c
> index cb8e6342eddf..45a92e3e8f2b 100644
> --- a/drivers/iio/adc/hi8435.c
> +++ b/drivers/iio/adc/hi8435.c
> @@ -141,10 +141,21 @@ static int hi8435_write_event_config(struct iio_dev *idev,
> enum iio_event_direction dir, int state)
> {
> struct hi8435_priv *priv = iio_priv(idev);
> + int ret;
> + u32 tmp;
> +
> + if (state) {
> + ret = hi8435_readl(priv, HI8435_SO31_0_REG, &tmp);
> + if (ret < 0)
> + return ret;
> + if (tmp & BIT(chan->channel))
> + priv->event_prev_val |= BIT(chan->channel);
> + else
> + priv->event_prev_val &= ~BIT(chan->channel);
>
> - priv->event_scan_mask &= ~BIT(chan->channel);
> - if (state)
> priv->event_scan_mask |= BIT(chan->channel);
> + } else
> + priv->event_scan_mask &= ~BIT(chan->channel);
>
> return 0;
> }
>

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