linux-kernel - Re: [PATCH v2 1/2] dt-bindings: iio: temperature: add support for MCP998X

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Message-ID: <91c1d757a4ac051c115a821779a8c1fba764ea05.camel@microchip.com>
Date: Mon, 2 Jun 2025 14:48:52 +0000
From: <Victor.Duicu@...rochip.com>
To: <conor@...nel.org>, <dlechner@...libre.com>
CC: <nuno.sa@...log.com>, <linux-iio@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <robh@...nel.org>, <jic23@...nel.org>,
	<krzk+dt@...nel.org>, <andy@...nel.org>, <linux-kernel@...r.kernel.org>,
	<Marius.Cristea@...rochip.com>, <conor+dt@...nel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: iio: temperature: add support for
 MCP998X

On Fri, 2025-05-30 at 16:55 +0100, Conor Dooley wrote:
> On Thu, May 29, 2025 at 01:13:38PM -0500, David Lechner wrote:
> > On 5/29/25 4:36 AM, victor.duicu@...rochip.com wrote:
> > > From: Victor Duicu <victor.duicu@...rochip.com>
> > > 
> > > 
Hi Conor,

...

> > > +  microchip,recd12:
> > > +    description:
> > > +      Enable resistance error correction for external channels 1
> > > and 2.
> > > +      Omit this tag to disable REC for channels 1 and 2.
> > > +    type: boolean
> > > +
> > > +  microchip,recd34:
> > > +    description:
> > > +      Enable resistance error correction for external channels 3
> > > and 4.
> > > +      Omit this tag to disable REC for channels 3 and 4.
> 
> Why are these two devicetree properties, rather than runtime
> controls?

The parasitic resistance added to the series resistance is dependent
only on the circuit. 
It is possible for the chip and the transistor to be at some distance
from each other. The manufacturer can approximate the error added and
decide if resistance error correction should be applied.
The user cannot influence the parasitic resistance nor calculate it.

With Kind Regards,
Victor Duicu