linux-kernel - Re: [PATCH v3 02/13] dt-bindings: hwmon: Add Apple System Management Controller hwmon schema

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Message-ID: <175997061547.377977.15400204653916198003.robh@kernel.org>
Date: Wed, 8 Oct 2025 19:43:41 -0500
From: "Rob Herring (Arm)" <robh@...nel.org>
To: James Calligeros <jcalligeros99@...il.com>
Cc: linux-input@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-rtc@...r.kernel.org, asahi@...ts.linux.dev,
	linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	linux-doc@...r.kernel.org,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	devicetree@...r.kernel.org, linux-hwmon@...r.kernel.org,
	Alyssa Rosenzweig <alyssa@...enzweig.io>,
	Janne Grunau <j@...nau.net>, Lee Jones <lee@...nel.org>,
	Jean Delvare <jdelvare@...e.com>,
	linux-arm-kernel@...ts.infradead.org,
	Conor Dooley <conor+dt@...nel.org>,
	Guenter Roeck <linux@...ck-us.net>, Neal Gompa <neal@...pa.dev>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Sven Peter <sven@...nel.org>
Subject: Re: [PATCH v3 02/13] dt-bindings: hwmon: Add Apple System Management
 Controller hwmon schema


On Tue, 07 Oct 2025 21:16:43 +1000, James Calligeros wrote:
> Apple Silicon devices integrate a vast array of sensors, monitoring
> current, power, temperature, and voltage across almost every part of
> the system. The sensors themselves are all connected to the System
> Management Controller (SMC). The SMC firmware exposes the data
> reported by these sensors via its standard FourCC-based key-value
> API. The SMC is also responsible for monitoring and controlling any
> fans connected to the system, exposing them in the same way.
> 
> For reasons known only to Apple, each device exposes its sensors with
> an almost totally unique set of keys. This is true even for devices
> which share an SoC. An M1 Mac mini, for example, will report its core
> temperatures on different keys to an M1 MacBook Pro. Worse still, the
> SMC does not provide a way to enumerate the available keys at runtime,
> nor do the keys follow any sort of reasonable or consistent naming
> rules that could be used to deduce their purpose. We must therefore
> know which keys are present on any given device, and which function
> they serve, ahead of time.
> 
> Add a schema so that we can describe the available sensors for a given
> Apple Silicon device in the Devicetree.
> 
> Reviewed-by: Neal Gompa <neal@...pa.dev>
> Signed-off-by: James Calligeros <jcalligeros99@...il.com>
> ---
>  .../bindings/hwmon/apple,smc-hwmon.yaml  | 86 +++++++++++++++++++++++++
>  .../bindings/mfd/apple,smc.yaml          | 36 +++++++++++
>  MAINTAINERS                              |  1 +
>  3 files changed, 123 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@...nel.org>