linux-kernel - Re: [PATCH 0/2] Add support for Microchip EMC1812

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Message-ID: <36c4794d-2116-4d3e-8ad5-ac3ec764a7a1@roeck-us.net>
Date: Thu, 25 Sep 2025 07:32:22 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Marius.Cristea@...rochip.com
Cc: jic23@...nel.org, dlechner@...libre.com, linux-hwmon@...r.kernel.org,
	jdelvare@...e.com, nuno.sa@...log.com, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, robh@...nel.org,
	linux-kernel@...r.kernel.org, andy@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org
Subject: Re: [PATCH 0/2] Add support for Microchip EMC1812

On Thu, Sep 25, 2025 at 09:09:04AM +0000, Marius.Cristea@...rochip.com wrote:
> Hi Guenter,
> 
> Thank you for the feedback.
> 
> On Tue, 2025-09-23 at 19:11 -0700, Guenter Roeck wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you
> > know the content is safe
> > 
> > On 9/20/25 04:33, Jonathan Cameron wrote:
> > > On Wed, 17 Sep 2025 15:21:56 +0300
> > > Marius Cristea <marius.cristea@...rochip.com> wrote:
> > > 
> > > > This is the iio driver for EMC1812/13/14/15/33 multichannel Low-
> > > > Voltage
> > > > Remote Diode Sensor Family. The chips in the family have one
> > > > internal
> > > > and different numbers of external channels, ranging from 1
> > > > (EMC1812) to
> > > > 4 channels (EMC1815).
> > > > Reading diodes in anti-parallel connection is supported by
> > > > EMC1814, EMC1815
> > > > and EMC1833.
> > > > 
> > > > Current version of driver does not support interrupts, events and
> > > > data
> > > > buffering.
> > > Hi Marius,
> > > 
> > > For a temperature monitoring device like this, the opening question
> > > is
> > > always why not HWMON?
> > > 
> > > There are various reasons we have temp sensors in IIO but mostly
> > > they are not
> > > described as being monitors and this one is.
> > > 
> > > IIO may well be the right choice for this part, but good to lay out
> > > your
> > > reasoning and +CC the hwmon list and maintainers.  There is an
> > > emc1403
> > > driver already in hwmon, so perhaps compare and contrast with that.
> > > 
> > > I've +CC Jean, Guenter and list to save sending a v2 just to do
> > > that.
> > > 
> > 
> > At first glance it looks like the series is (mostly ?) register
> > compatible
> > to the chips supported by the emc1403 driver, so it should be
> > straightforward
> > to add support for the emc180x series to that driver.
> > 
> > Guenter
> 
> Most of the register address are compatible. The EMC181X is an update 
> (a newer generation) then the EMC1403.
> 
> The biggest improvement is that the EMC18XX has a continuous block of
> registers in order to improve the temperature reading (that means some
> addresses are overlapping with the older register maps) and a new set
> of registers to  handle the "Rate Of Change" functionality.
> Also the older EMC14XX has some hardcoded configuration/features based
> on the part number.
> 
> Considering all of the above I consider that the complexity of the
> EMC1403 will increase quite a lot without any real benefit and it will
> be harder to be maintained.
> 
Ok.

> I have submitted this as the fist iteration from a longer list of
> feature that I want to add to the driver, including events and maybe
> interrupts.
> 
> If nobody has anything against, I would like to add a separate driver
> for EMC18XX into the IIO.

IMO this should be a hwmon driver.

Guenter