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

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Message-ID: <2svr42ee7akwxwj5nizwe4a4hqdk4rslv7ivxraqg3jy6m3mxz@lfpn2nx4jdmm>
Date: Thu, 14 Aug 2025 15:15:29 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: nuno.sa@...log.com, 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>, 
	Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 0/6] mfd: Add support for the LTC4283 Hot Swap Controller

On Thu, Aug 14, 2025 at 05:54:26AM -0700, Guenter Roeck wrote:
> On 8/14/25 03:52, Nuno Sá via B4 Relay 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.
> > 
> > Also to note that the device has some similarities with the already
> > supported ltc4282 hwmon driver but it is different enough to be in it's own
> > driver (apart from being added as MFD). The register map is also fairly
> > different.
> > 
> > Last time (for the ltc4282) I tried to add the gpio bits directly in the
> > hwmon driver but Guenter did not really liked it and so this time I'm doing
> > it as MFD.
> > 
> Nowadays I suggest that people use auxiliary drivers in such situations.

I see. But do you have any issue with it being MFD?

I'm anyways tempted to the auxiliary device idea. The main usage for
this device is HWMON and I dunno anyone would use it only as a GPIO
controller. With the auxiliary device we would only need one bindings file
and slightly better bindings for the pins functionality.

- Nuno Sá

> 
> Guenter
>