Jonathan Cameron writes:
> 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.
Probably this should have been part of the commit message:
Tested on imx233-olinuxino with both DHT11 and DHT22 the following
patch combinations: 2+3 and 1+2+3.
Of course tests by people who already had problems with the driver in
the past are highly appreciated.
> Changes to this driver always worry me given how fiddly the hardware
> interface is.
Yeah, looks like I already got it wrong in various ways in the past.
Thanks,
Harald
> 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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