Messages in this thread | | | Date | Mon, 18 Apr 2016 23:04:48 +0530 | From | Laxman Dewangan <> | Subject | Re: [PATCH V3 2/2] thermal: generic-adc: Add ADC based thermal sensor driver |
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On Monday 18 April 2016 11:01 PM, Jonathan Cameron wrote: > > On 18 April 2016 17:49:39 BST, Laxman Dewangan <ldewangan@nvidia.com> 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.
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