Re: [PATCH V3 2/2] thermal: generic-adc: Add ADC based thermal sensor driver

[Laxman Dewangan]

On Monday 18 April 2016 11:01 PM, Jonathan Cameron wrote:
> On 18 April 2016 17:49:39 BST, Laxman Dewangan <ldewangan@xxxxxxxxxx> wrote:
> > On Sunday 17 April 2016 04:24 PM, Jonathan Cameron wrote:
> > > On 14/04/16 15:41, Laxman Dewangan wrote:
> > > +static int gadc_thermal_read_channel(struct gadc_thermal_info *gti,
> > int *val)
> > > +{
> > > +	int ret;
> > > +
> > > +	ret = iio_read_channel_processed(gti->channel, val);
> > > +	if (ret < 0)
> > > +		ret = iio_read_channel_raw(gti->channel, val);
> > > Is this case actually useful given it means the scaling of the adc
> > > isn't known?
> > >
> > > I suppose you might have defined the table in terms of raw readings,
> > > but then when someone comes along and 'fixes' the ADC driver to
> > output
> > > it's scale your table will be wrong.
> > Yes, that may be possible if someone just move the implementation of
> > processed read to raw read.
> > I assumed that some of adc driver implemented as raw and some of
> > implemented as processed and so fallback.
> >
> > However, if adc driver has processed implementation then it should not
> > move to raw and deprecate the processed.
> >
> > It seems raw as default should be better option. We can have two option
> > now:
> >
> > - Support raw only, not to processed.
> >
> > - Or support the raw as default and processed as the optional from DT.
> > if (!processed)
> >      read_raw()
> > else
> >    read_processed()
> >
> >
> > Your opinion?
> Processed only. It will compute the right value if raw and scale are provided by the
>   device (which they should be for an ADC). The read_processed function does
>   the maths if needed.
>
>   The only time devices should
>   supply raw without scale is if their is no direct transform ( e.g. an infrared
>   intensity measure where only known transform involves combining it with
>   another signal) or their is an external unknown (e.g. proximity sensors where
>   you have to know what they were close to in order to know the scaling!)
>
> If there is a conventional ADC driver not providing either processed directly or
>   both raw and scale let us know and we will fix it!

Thanks, I will recycle this patch to use processed only.