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

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Message-ID: <CACRpkdYQa21PeAHTUPY2XRVnknnDS+v3Ci8DGyiYSdJdYVJCEA@mail.gmail.com>
Date: Thu, 21 Aug 2025 14:06:10 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: nuno.sa@...log.com, Jonathan Cameron <jic23@...nel.org>, 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 Tue, Aug 19, 2025 at 6:11 PM Guenter Roeck <linux@...ck-us.net> wrote:
> 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.

It was mainly because the text talks about regulating currents and current
rush, and an onboard ADC. There is admittedly even a bit of regulator
framework-related business going on.

On second look it's fine to keep as hwmon, discard my previous
opinion, I should have looked closer and now I changed my mind.
I'ts good with some pushback!

Yours,
Linus Walleij