From 22acc120a141ce0a3b6e98799d15970ef687bc70 Mon Sep 17 00:00:00 2001 From: Harald Geyer Date: Sun, 17 Jan 2016 16:13:29 +0000 Subject: [PATCH] iio: dht11: Improve reliability - be more tolerant about missing start bits Instead of guessing where the data starts, we now just try to decode from every possible start position. This causes no additional overhead if we properly received the full preamble and only costs a few extra CPU cycles in the case where the preamble is corrupted. This is much more efficient than to return an error to userspace and start over again. Signed-off-by: Harald Geyer Signed-off-by: Jonathan Cameron --- drivers/iio/humidity/dht11.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c index 1165b1c4f9d6..1ca284aaacfc 100644 --- a/drivers/iio/humidity/dht11.c +++ b/drivers/iio/humidity/dht11.c @@ -161,7 +161,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev, int *val, int *val2, long m) { struct dht11 *dht11 = iio_priv(iio_dev); - int ret, timeres; + int ret, timeres, offset; mutex_lock(&dht11->lock); if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) { @@ -208,11 +208,14 @@ static int dht11_read_raw(struct iio_dev *iio_dev, if (ret < 0) goto err; - ret = dht11_decode(dht11, - dht11->num_edges == DHT11_EDGES_PER_READ ? - DHT11_EDGES_PREAMBLE : - DHT11_EDGES_PREAMBLE - 2, - timeres); + offset = DHT11_EDGES_PREAMBLE + + dht11->num_edges - DHT11_EDGES_PER_READ; + for (; offset >= 0; --offset) { + ret = dht11_decode(dht11, offset, timeres); + if (!ret) + break; + } + if (ret) goto err; }