iio: hi8435: avoid garbage event at first enable
authorNikita Yushchenko <nikita.yoush@cogentembedded.com>
Fri, 19 May 2017 14:48:00 +0000 (17:48 +0300)
committerJonathan Cameron <jic23@kernel.org>
Sat, 20 May 2017 16:33:52 +0000 (17:33 +0100)
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>
drivers/iio/adc/hi8435.c

index cb8e6342eddfad96793db3c87adf5171c8e96bc0..45a92e3e8f2b6e88289eac6073a251e3983135bd 100644 (file)
@@ -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;
 }