linux-kernel - Re: [PATCH 0/6] mfd: Add support for the LTC4283 Hot Swap Controller

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Message-ID: <5f456224-d26f-4cca-a2f2-31418da287c2@roeck-us.net>
Date: Tue, 19 Aug 2025 09:10:57 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Linus Walleij <linus.walleij@...aro.org>, nuno.sa@...log.com,
 Jonathan Cameron <jic23@...nel.org>
Cc: linux-hwmon@...r.kernel.org, linux-gpio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, Lee Jones <lee@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Jean Delvare <jdelvare@...e.com>,
 Jonathan Corbet <corbet@....net>, Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 0/6] mfd: Add support for the LTC4283 Hot Swap Controller

On 8/19/25 05:36, Linus Walleij wrote:
> On Thu, Aug 14, 2025 at 12:52 PM Nuno Sá via B4 Relay
> <devnull+nuno.sa.analog.com@...nel.org> wrote:
> 
>> The LTC4283 device features programmable current limit with foldback and
>> independently adjustable inrush current to optimize the MOSFET safe
>> operating area (SOA). The SOA timer limits MOSFET temperature rise for
>> reliable protection against overstresses.
>>
>> An I2C interface and onboard ADC allow monitoring of board current, voltage,
>> power, energy, and fault status.
>>
>> It also features 8 pins that can be configured as GPIO devices. But since
>> the main usage for this device is monitoring, the GPIO part is optional
>> while the HWMON is being made as required.
> 
> This main device just screams Industrial I/O, IIO.
> 

Really ? I would have assumed that the sensors on a chip like this are supposed
to be used for hardware monitoring, and that IIO is supposed to be used in cases
where the data itself is the relevant information. What exactly makes a hot swap
controller screaming IIO ? Am I missing something here ?

I am not going to argue about this if IIO wants to extend into hardware monitoring,
I just wonder about the rationale behind it.

Thanks,
Guenter

> (I think it's fine to use an MFD core and split off GPIO to a
> separate driver, and I suggest maybe you merge MFD and
> GPIO ahead of the main driver.)
> 
> Jonathan (Cameron) will have the last word on it but IMO this firmly
> belongs below drivers/iio.
> 
> Perhaps not in one of the existing subdirs there but then it is time to
> be brave and create a new one.
> 
> It will take some time and consideration, but I think it would be better
> for everyone.
> 
> Yours,
> Linus Walleij
>