linux-kernel - Re: [PATCH v1 09/13] iio: chemical: bme680: Move ambient temperature to attributes

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Message-ID: <20241019145925.5d54e7b4@jic23-huawei>
Date: Sat, 19 Oct 2024 14:59:25 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: lars@...afoo.de, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, anshulusr@...il.com, gustavograzs@...il.com,
 andriy.shevchenko@...ux.intel.com, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 09/13] iio: chemical: bme680: Move ambient
 temperature to attributes

On Mon, 14 Oct 2024 22:14:23 +0200
Vasileios Amoiridis <vassilisamir@...il.com> wrote:

> On Sat, Oct 12, 2024 at 01:01:24PM +0100, Jonathan Cameron wrote:
> > On Thu, 10 Oct 2024 23:00:26 +0200
> > vamoirid <vassilisamir@...il.com> wrote:
> >   
> > > From: Vasileios Amoiridis <vassilisamir@...il.com>
> > > 
> > > Remove the ambient temperature from being a macro and implement it as
> > > an attribute. This way, it is possible to dynamically configure the
> > > ambient temperature of the environment to improve the accuracy of the
> > > measurements.
> > > 
> > > Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>  
> > New ABI? Would need docs.
> > 
> > However, I 'think' we have a few cases where we handle this via the slightly
> > odd interface of out_temp_processed / _raw with a label saying it's
> > ambient temperature.
> > 
> > The tenuous argument is that we have heaters that actually control the
> > temperature and the affect of either heating the thing or just happening
> > to know the external temperature ends up being the same. Hence use
> > an output channel for this control.
> > 
> > Jonathan  
> 
> Hi Jonathan,
> 
> Thanks for taking the time to review this. I saw your previous messages,
> and I am not responding to all of them so as to not flood you with ACK
> messages.
> 
> For this one though I have to ask. The last commit of this series is
> adding support for an output current channel that controls the current
> that is being inserted into an internal plate that is heated up in order
> to have more precise acquisition of humidity and gas measurement. Does
> it makes sense to add an ambient temp output channel as well?

If we need to know that temperature to calculate the meaning of the pressure
channels then I think it does.

I am a little confused though as this device measures the temperature.
Why isn't that the right value to use?  Is that because the heater
is confusing things?


> 
> Cheers,
> Vasilis
>