Re: [PATCH 0/4] Add valid sample channel

[Lars-Peter Clausen <lars@metafoo.de>]

On 11/26/2014 01:58 PM, Daniel Baluta wrote:
> On Tue, Nov 25, 2014 at 7:29 PM, Jonathan Cameron <jic23@kernel.org> wrote:
>>
>>
>> On November 25, 2014 5:00:11 PM GMT+00:00, Lars-Peter Clausen <lars@metafoo.de> wrote:
>>> On 11/25/2014 05:55 PM, Daniel Baluta wrote:
>>>> On Tue, Nov 25, 2014 at 6:36 PM, Lars-Peter Clausen <lars@metafoo.de>
>>> 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.
>
> I think this makes a lot of sense for kmx61 and offers a cleaner
> interface to user space.
>
>>>
>>> - 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!
>
> I looked into iio/adc/ and iio/imu/ but couldn't find any driver which
> has one IIO device  and multiple buffers. I don't see how this can
> work :).
>
> User space application will read /dev/iio:deviceX to get data
> samples. How would they know the source of the data samples?

What exactly do you mean by source?

>
> Let me know where is the source code for the 8 buffers ADC driver,
> I am very curious about the implementation :).

I think that one never made it into upstream or got reworked before.

- Lars