linux-kernel - Re: Question about nct6775 regarding MFD

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Message-ID: <074a2561-1c9b-4138-9ade-bdd1b34825f2@roeck-us.net>
Date: Mon, 16 Jun 2025 05:14:48 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: "Niedermayr, BENEDIKT" <benedikt.niedermayr@...mens.com>,
 "zev@...ilderbeest.net" <zev@...ilderbeest.net>,
 "jdelvare@...e.com" <jdelvare@...e.com>
Cc: "Lopes Ivo, Diogo Miguel" <diogo.ivo@...mens.com>,
 "Kiszka, Jan" <jan.kiszka@...mens.com>,
 "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Question about nct6775 regarding MFD

On 6/16/25 03:34, Niedermayr, BENEDIKT wrote:
> Hi folks,
> 
> we are currently refactoring some parts of the
> "drivers/platform/x86/siemens/*" which has references to some
> 
> Nuvoton Super-I/O chips. One of them is the nct6775.
> 
> The driver in question is not implemented as MFD, even though MFD would
> have fit perfectly for it (or am I wrong?).
> 
> 
> My question now:
> 
> Why wasn't the driver implemented as an MFD? Was MFD discussed during
> your upstreaming-related conversations?
> 

Super-IO chips have historically not been implemented as MFD since the functionality
is well separated except for configuration register access, and that is well handled
with the various superio_enter() functions which use a multiplexed memory region
to (temporarily) request chip access. Implementing those drivers as MFD would only
add complexity with no gain or benefit.

Guenter