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

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Jun 28, 2013 at 05:24:43PM +0200, Lars-Peter Clausen wrote:
> 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.
> 
Agreed.

Guenter