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

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Message-ID: <e6ab5becf5908d83857fcfd57823ffd259e6db90.camel@microchip.com>
Date: Thu, 25 Sep 2025 09:09:04 +0000
From: <Marius.Cristea@...rochip.com>
To: <linux@...ck-us.net>, <jic23@...nel.org>
CC: <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

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
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> 
> 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.

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.

Thanks and Best Regards,
Marius