On Thu, May 31, 2018 at 7:31 AM, Phil Reid <preid@xxxxxxxxxxxxxxxxx> wrote: > On 30/05/2018 22:23, Tomasz Duszynski wrote: >> >> On Wed, May 30, 2018 at 03:20:37PM +0800, Matt Ranostay wrote: >>> >>> On Wed, May 30, 2018 at 1:05 PM, Matt Ranostay >>> <matt.ranostay@xxxxxxxxxxxx> wrote: >>>> >>>> On Wed, May 30, 2018 at 9:17 AM, Phil Reid <preid@xxxxxxxxxxxxxxxxx> >>>> wrote: >>>>> >>>>> On 30/05/2018 08:44, Matt Ranostay wrote: >>>>>> >>>>>> >>>>>> On Mon, May 28, 2018 at 11:38 PM, Tomasz Duszynski >>>>>> <tduszyns@xxxxxxxxx> >>>>>> wrote: >>>>>>> >>>>>>> >>>>>>> According to IIO ABI relative humidity reading should be >>>>>>> returned in milli percent. >>>>>>> >>>>>>> This patch addresses that by applying proper scaling and >>>>>>> returning integer instead of fractional format type specifier. >>>>>>> >>>>>> >>>>>> *sigh* seems this is my mistake, but good catch. Slight nitpick >>>>>> below.. otherwise looks good >>>>>> >>>>>>> Signed-off-by: Tomasz Duszynski <tduszyns@xxxxxxxxx> >>>>>>> --- >>>>>>> drivers/iio/pressure/bmp280-core.c | 5 ++--- >>>>>>> 1 file changed, 2 insertions(+), 3 deletions(-) >>>>>>> >>>>>>> diff --git a/drivers/iio/pressure/bmp280-core.c >>>>>>> b/drivers/iio/pressure/bmp280-core.c >>>>>>> index 5ec3e41b65f2..fe87d27779d9 100644 >>>>>>> --- a/drivers/iio/pressure/bmp280-core.c >>>>>>> +++ b/drivers/iio/pressure/bmp280-core.c >>>>>>> @@ -415,10 +415,9 @@ static int bmp280_read_humid(struct bmp280_data >>>>>>> *data, int *val, int *val2) >>>>>>> } >>>>>>> comp_humidity = bmp280_compensate_humidity(data, >>>>>>> adc_humidity); >>>>>>> >>>>>>> - *val = comp_humidity; >>>>>>> - *val2 = 1024; >>>>>>> + *val = comp_humidity * 1000 / 1024; >>>>>> >>>>>> >>>>>> >>>>>> Minor nitpick that it would look cleaner as: (comp_humidity / 1024) >>>>>> * >>>>>> 1000 >>>>>> >>>>> be careful of integer division. >>>>> >>>> >>>> Ah yes good point. You will have to check if comp_humidity isn't zero >>>> or it is possible to have a divide-by-zero. >>> >>> >>> D'oh actually divide by zero would be an issue. But you'll want to be >>> sure of possible overflows (doubt that would be an issue here). >> >> >> What kind of division-by-zero are you meaning? When would that happen >> in this case? >> > > I meant something like this: > > 10 / 1024 = 0 > 0 * 1000 = 0 > > 10 * 1000 = 10000 > 10000 / 1024 = 9 > > patch looks like the right way to me > provided comp_humidity * 1000 is not going to overflow. > > Ah right.. forgot about order of operations does matter in integer division. > >>> >>> However it may be better to just add the scaling factor of 1000 with >>> IIO_CHAN_INFO_SCALE and make the processed value now a raw one. >> >> >> Is measurement precision your concern here? I would not bother with that >> since the sensor is not a top-notch anyway. Even datasheet itself >> specifies >> error margin of +/-3% for relative humidity. >> >>> >>>> >>>> - Matt >>>> >>>>> >>>>>>> >>>>>>> - return IIO_VAL_FRACTIONAL; >>>>>>> + return IIO_VAL_INT; >>>>>>> } >>>>>>> >>>>>>> static int bmp280_read_raw(struct iio_dev *indio_dev, >>>>>>> -- >>>>>>> 2.17.0 >>>>> >>>>> >>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> Regards >>>>> Phil Reid >>>>> >> >> > > > -- > Regards > Phil Reid > > ElectroMagnetic Imaging Technology Pty Ltd > Development of Geophysical Instrumentation & Software > www.electromag.com.au > > 3 The Avenue, Midland WA 6056, AUSTRALIA > Ph: +61 8 9250 8100 > Fax: +61 8 9250 7100 > Email: preid@xxxxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
