From a1aeeacc646dc2e576512988b7f721751c0373ef Mon Sep 17 00:00:00 2001 From: Nikita Yushchenko Date: Fri, 19 May 2017 17:48:00 +0300 Subject: [PATCH] iio: hi8435: avoid garbage event at first enable [ 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 Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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 678e8c7..52b2dcf 100644 --- a/drivers/iio/adc/hi8435.c +++ b/drivers/iio/adc/hi8435.c @@ -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; } -- 2.7.4