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iio: hi8435: avoid garbage event at first enable 

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>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Nikita Yushchenko 2017-05-19 17:48:00 +03:00 committed by Jonathan Cameron
parent fa7662e1bd
commit ee19ac340c
1 changed files with 13 additions and 2 deletions
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15
drivers/iio/adc/hi8435.c
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@ -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;
}