On 30/12/15 14:26, Harald Geyer wrote:
> 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 <harald@xxxxxxxxx>
Seems sensible, but ideally I'd like a tested by! Sounds like
Jonathan Bell might be able to provide one.
Changes to this driver always worry me given how fiddly the hardware
interface is.
Jonathan
> ---
> Jonathan Bell:
> Can you test if this fixes the problems you reported on RPi?
>
> (It does fix problems I noticed when I slowed down my test HW with
> enabling the debug logging introduced later in this series, so including
> this patch is a good thing even if it doesn't fix Jonathan's problems.)
>
> 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 1165b1c..1ca284a 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;
> }
>
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