linux-kernel - Re: [PATCH v6 0/2] add support for MCP998X

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Message-ID: <44a1a1c4-813d-4540-a73e-b136032e79a2@roeck-us.net>
Date: Sat, 4 Oct 2025 07:29:05 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Jonathan Cameron <jic23@...nel.org>, victor.duicu@...rochip.com
Cc: dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 marius.cristea@...rochip.com, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH v6 0/2] add support for MCP998X

On 10/4/25 07:11, Jonathan Cameron wrote:
> On Tue, 30 Sep 2025 16:31:29 +0300
> <victor.duicu@...rochip.com> wrote:
> 
>> From: Victor Duicu <victor.duicu@...rochip.com>
>>
>> Add support for Microchip MCP998X/33 and MCP998XD/33D Multichannel
>> Automotive Temperature Monitor Family.
>>
>> The chips in the family have different numbers of external channels,
>> ranging from 1 (MCP9982) to 4 channels (MCP9985). Reading diodes in
>> anti-parallel connection is supported by MCP9984/85/33 and
>> MCP9984D/85D/33D. Dedicated hardware shutdown circuitry is present
>> only in MCP998XD and MCP9933D.
>>
>> This driver was submitted in the IIO subsystem because the chips could use
>> interrupts to handle threshold events.
> 
> This reasoning isn't particularly strong as hwmon has support for events etc.
> This device is also 'slow' so I'm not immediately seeing a strong reason why
> IIO is the right choice.
> 

Correct. hwmon supports both events and udev events.

> After some recent feedback from Guenter I'm keen to get a clearer set
> of reasoning when I take a temperature monitoring chip into IIO.
> 
> Also asking that we +CC Guenter for his input on devices where the decision
> isn't clear cut.

IMO this _is_ (or should be) clear cut: This is a hardware monitoring device.
It should be a hardware monitoring driver. FWIW, writing one should be
straightforward (including interrupt/event support).

Guenter