On Tue, Nov 25, 2014 at 7:29 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > > > On November 25, 2014 5:00:11 PM GMT+00:00, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote: >>On 11/25/2014 05:55 PM, Daniel Baluta wrote: >>> On Tue, Nov 25, 2014 at 6:36 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> >>wrote: >>>> On 11/25/2014 01:48 PM, Vlad Dogaru wrote: >>>>> >>>>> This is an attempt to address the problem of buffering in devices >>which >>>>> have >>>>> different scan frequencies for different channels. >>>> >>>> >>>> Will these frequencies still be related or completely arbitrary? >>> >>> For Kionix KMX61 we have the same set of frequencies for >>> accelerometer and magnetometer (12.5, 25, 50, 100 Hz, etc) >>> but for example at some point accel can be configured with 100 Hz >>> and magnetometer with 12.5Hz. >>> >>> Does this matter? >> >>I'm wondering if it makes more sense to register multiple buffers or >>devices >>if the frequencies are completely unrelated. E.g. in the KMX61 case it >>looks >>as if its simply two logical devices in the same physical package. >> >>- Lars > That is how we have handled this so far. > Sometimes we have separate iio_devices for > the logical functions e.g. hid-sensors and sometimes just multiple buffers.. I am > struggling to find it now but one of the ADC drivers had a insanely complex nest > sampling arrangement requiring 8 buffers. Final driver might have been simplified though... We might still need a few tweaks > for multiple buffers not to having naming clashes.... Moving house so only have phone to hand! > The main usage I see for a single device / buffer and multiple channels is to reduce the user/kernel context switch overhead in a sensor hub environment with lots of sensors (i.e. do a single read instead of one for each sensor). The improvements are going to be even bigger if the sensor hub supports a hardware buffer. Some people are quite vocal about that, although I didn't see data that can be used to draw a relevant conclusion yet. Time to do some experiments, I guess :) -- 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
