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

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Message-ID: <de899dde-c0cf-477d-8240-50fbdcbe736a@roeck-us.net>
Date: Thu, 14 Aug 2025 14:57:44 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Nuno Sá <noname.nuno@...il.com>
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 8/14/25 07:15, Nuno Sá wrote:
> 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 only object to squeezing non-hwmon code into hwmon drivers, especially since
a relatively low-overhead alternative is now available. I would not want to
implement a driver such as this one as set of mfd drivers myself, but I won't
object to it either.

Guenter