From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Date: Mon, 01 Jun 2015 23:48:33 +0000 Subject: Re: [lm-sensors] [PATCH v3] hwmon: ntc: fix iio raw to microvolts conversion Message-Id: <556CEF51.50100@roeck-us.net> List-Id: References: <1433176057-26446-1-git-send-email-chris.lesiak@licor.com> In-Reply-To: <1433176057-26446-1-git-send-email-chris.lesiak@licor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lm-sensors@vger.kernel.org On 06/01/2015 03:06 PM, Chris Lesiak wrote: [ ... ] . >>> >>> I think things could be improved in one of two ways: >>> 1. Accept the precision that you get by doing the calculation millivolts. >>> Simplify things by using millivolts throughout, although pullup_uv >>> needs to remain becaus it is part of the interface. >>> 2. Create an additional patch doing the calculations with microvolts >>> instead of millivolts. >>> >>> What are your thoughts? >>> >> >> You explain above that doing the calculations in mV looses precision. >> Given that, what would be the point of the first proposal, especially >> since the uV are already available (and may still be needed in >> ntc_adc_iio_read if conversion through iio is not available) ? >> >> Thanks, >> Guenter >> > > I do think that option 2 is the better choice. If you'd like, I'll create a patch. > Your call. > But if 1 were implemented, ntc_adc_iio_read would give a value in millivolts > even when iio_convert_raw_to_processed failed. Something like: > > ret = iio_convert_raw_to_processed(channel, raw, &mv, 1); > if (ret < 0) { > /* Assume 12 bit ADC with vref at pullup_uv*/ > mv = (pdata->pullup_uv * (s64)raw / 1000) >> 12; > } > But what would be the point ? I don't see how that would improve anything. Since iio internally supports uV, at least optionally, you would then always loose accuracy. So we might as well leave everything as-is. Thanks, Guenter _______________________________________________ lm-sensors mailing list lm-sensors@lm-sensors.org http://lists.lm-sensors.org/mailman/listinfo/lm-sensors