On Tue, Aug 19, 2025 at 09:47:54PM +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. I'm confused because you say this, but then the .dtsi files are common. > > Add a schema so that we can describe the available sensors for a given > Apple Silicon device in the Devicetree. > > Signed-off-by: James Calligeros <jcalligeros99@xxxxxxxxx> > --- > .../bindings/hwmon/apple,smc-hwmon.yaml | 148 +++++++++++++++++++++++++ > .../bindings/mfd/apple,smc.yaml | 45 ++++++++ > 2 files changed, 193 insertions(+) > > diff --git a/Documentation/devicetree/bindings/hwmon/apple,smc-hwmon.yaml b/Documentation/devicetree/bindings/hwmon/apple,smc-hwmon.yaml > new file mode 100644 > index 0000000000000000000000000000000000000000..3ebc0463be4e1ce54005418feaa87ec7254dab6e > --- /dev/null > +++ b/Documentation/devicetree/bindings/hwmon/apple,smc-hwmon.yaml > @@ -0,0 +1,148 @@ > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/hwmon/apple,smc-hwmon.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: Apple SMC Hardware Monitoring > + > +description: > + Apple's System Management Controller (SMC) exposes a vast array of > + hardware monitoring sensors, including temperature probes, current and > + voltage sense, power meters, and fan speeds. It also provides endpoints > + to manually control the speed of each fan individually. Each Apple > + Silicon device exposes a different set of endpoints via SMC keys. This > + is true even when two machines share an SoC. The CPU core temperature > + sensor keys on an M1 Mac mini are different to those on an M1 MacBook > + Pro, for example. > + > +maintainers: > + - James Calligeros <jcalligeros99@xxxxxxxxx> > + > +properties: > + compatible: > + const: apple,smc-hwmon > + > + current: I don't see any need to group these and I would remove the intermediate node. We have an iterator to iterate over a matching node name prefix if that was the reasoning. > + description: SMC current sense endpoints > + type: object > + additionalProperties: false blank line > + patternProperties: > + "^current-[A-Za-z0-9]{4}": Missing a '$' anchor on the end. > + type: object > + additionalProperties: false blank line. > + required: > + - apple,key-id 'required' goes after 'properties'. blank lines in between. > + properties: > + apple,key-id: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: The SMC FourCC key of the desired current sensor. > + Should match the node's suffix, but doesn't have to. blank line > + label: > + $ref: /schemas/types.yaml#/definitions/string Already has a type, don't need to re-define it. > + description: Human-readable name for the sensor Instead of duplicating these properties, You can do it once under a '$defs' key and then reference it here. > + > + fan: > + description: SMC fan control endpoints. A fan is made up of five > + SMC keys - the fan's current speed, its minimum speed, its maximum > + speed, a writeable target speed, and a writeable mode. The SMC will > + automatically manage system fans unless a 1 is written to the fan's > + mode key. > + type: object > + additionalProperties: false blank line. And so on... > + patternProperties: > + "^fan-[A-Za-z0-9]{4}": > + type: object > + additionalProperties: false > + required: > + - apple,key-id > + properties: > + apple,key-id: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: The SMC FourCC key of the desired fan. This is the > + main key, which reports the fan's current speed. Sould match typo > + the node's suffix, but doesn't have to. Why can't we require that they match? (Other than we can't express that in schema?) > + apple,fan-minimum: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: The minimum speed the current fan can run at This is not the speed, but the identifier key to retrieve the min speed, right? That's not clear. It's a bit odd that everything is a key id, but one property has that in the name and the others don't. I don't have any better suggestion though... > + apple,fan-maximum: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: The maximum speed the current fan can run at > + apple,fan-target: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: Writeable endpoint for setting desired fan speed > + apple,fan-mode: > + $ref: /schemas/types.yaml#/definitions/string > + pattern: "^[A-Za-z0-9]{4}" > + description: Writeable endpoint to enable/disable manual fan > + control > + label: > + $ref: /schemas/types.yaml#/definitions/string > + description: Human-readable name for the sensor Surely more than apple,key-id is required? How would it be useful with only that? You can know how many fans you have, but have no info or control over them? Rob
