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iio: hi8435: avoid garbage event at first enable

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[ Upstream commit ee19ac340c5fdfd89c6348be4563453c61ab54a9 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nikita Yushchenko 2017-05-19 17:48:00 +03:00 committed by Greg Kroah-Hartman
parent 1799ba22a8
commit ce839ed818
1 changed files with 13 additions and 2 deletions
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15
drivers/iio/adc/hi8435.c
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@ -121,10 +121,21 @@ 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;
}