Re: [PATCH 3/4] hwmon: Add a simple driver to read the MXS SoC temperature

[Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>]

On 06/28/2013 04:50 PM, Alexandre Belloni wrote:
> On 28/06/2013 16:18, Lars-Peter Clausen wrote:
>> On 06/27/2013 09:26 PM, Alexandre Belloni wrote:
>>>
>>> They are already registered as IIO_TEMP but only implement read_raw. Also,
>>>
>>> iio_hwmon_read_val() is using iio_read_channel_processed() and that will
>>> basically only read one of the 2 channels. As I documented, you actually
>>> need to read both channel 8 and channel 9 and then compute the value in
>>> Kelvins. I'm not sure how you want me to do that in the current framework.
>> What are these two channels actually measuring? Is the value of a single
>> channel meaningful on it's own? If not it might make sense to update the IIO
>> driver to just have one temperature channel.
> 
> It's not actually meaningful on its own. So, what you would do is expose
> one iio channel for two ADC channels and do the computation in read_raw
> ? or read_processed ? Then using iio-hwon to export it. ?
> 
> Regards,
> 

Yes, return channel9 - channel8 as the raw value for the temperature channel
and provide proper scale and offset values, so that
iio_read_channel_processed() will return the correct value.

- Lars