linux-kernel - Re: [PATCH v3 2/2] thermal: thermal-generic-adc: add temperature sensor channel

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Message-ID: <20250405161504.6d2cc27d@jic23-huawei>
Date: Sat, 5 Apr 2025 16:15:04 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>
Cc: Svyatoslav Ryhel <clamor95@...il.com>, linux-pm@...r.kernel.org,
 devicetree@...r.kernel.org, Laxman Dewangan <ldewangan@...dia.com>, Conor
 Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Rob
 Herring <robh@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>,
 Zhang Rui <rui.zhang@...el.com>, linux-kernel@...r.kernel.org, "Rafael J.
 Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v3 2/2] thermal: thermal-generic-adc: add temperature
 sensor channel

On Thu, 6 Mar 2025 10:04:01 +0000
Lukasz Luba <lukasz.luba@....com> wrote:

> On 3/6/25 09:49, Svyatoslav Ryhel wrote:
> > ср, 5 бер. 2025 р. о 16:37 Lukasz Luba <lukasz.luba@....com> пише:  
> >>
> >>
> >>
> >> On 3/5/25 10:06, Svyatoslav Ryhel wrote:  
> >>> ср, 5 бер. 2025 р. о 11:52 Lukasz Luba <lukasz.luba@....com> пише:  
> >>>>
> >>>>
> >>>>
> >>>> On 3/3/25 12:21, Svyatoslav Ryhel wrote:  
> >>>>> To avoid duplicating sensor functionality and conversion tables, this design
> >>>>> allows converting an ADC IIO channel's output directly into a temperature IIO
> >>>>> channel. This is particularly useful for devices where hwmon isn't suitable
> >>>>> or where temperature data must be accessible through IIO.
> >>>>>
> >>>>> One such device is, for example, the MAX17040 fuel gauge.
> >>>>>
> >>>>> Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> >>>>> ---
> >>>>>     drivers/thermal/thermal-generic-adc.c | 54 ++++++++++++++++++++++++++-
> >>>>>     1 file changed, 53 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/drivers/thermal/thermal-generic-adc.c b/drivers/thermal/thermal-generic-adc.c  
> >>> ...  
> >>>>>
> >>>>> +static const struct iio_chan_spec gadc_thermal_iio_channel[] = {
> >>>>> +     {
> >>>>> +             .type = IIO_TEMP,
> >>>>> +             .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),  
> >>>>
> >>>> I would add the IIO_CHAN_INFO_SCALE and say it's in milli-degrees.
> >>>>  
> >>>
> >>> I have hit this issue already with als sensor. This should definitely
> >>> be a IIO_CHAN_INFO_PROCESSED since there is no raw temp data we have,
> >>> it gets processed into temp data via conversion table. I will add
> >>> Jonathan Cameron to list if you don't mind, he might give some good
> >>> advice.  
> >>
> >> I'm not talking about 'PROCESSED' vs 'RAW'...
> >> I'm asking if you can add the 'SCALE' case to handle and report
> >> that this device will report 'processed' temp value in milli-degrees
> >> of Celsius.
> >>  
> > 
> > It seems that SCALE is not applied to PROCESSED channel. I can use RAW
> > which would work as intended and I will add a note in commit
> > description why I used RAW. Would that be acceptable?

Indeed. SCALE is only about RAW channels because if they are processed
you have already applied the scale (typically because it wasn't linear)

> >   
> 
> In that case, yes that would be the preferred solution.

I nearly missed this entirely as it was buried in my unfiltered email.
Thanks for the +CC.

Given this is a IIO driver (be it in thermal)
please +CC linux-iio@...r.kernel.org to get review of that part of it.

Note, in general if you do a driver out of subsystem (and there
are good reasons to do that!) please +CC the other subsystem and
maintainers as well. We do that for IIO drivers that have a gpio
chip for instance. I specifically check they are +CC and wait for
an Ack before merging such drivers.

Thanks,

Jonathan