Re: [RFC PATCH 1/2] platform: arm64: qcom-hamoa-ec: monitor Slim 7x legacy sensors

From: Guenter Roeck

Date: Tue Sep 08 2026 - 01:25:19 EST


On 9/7/26 18:57, Birk Skyum wrote:
The Yoga Slim 7x EC returns an all-zero response to the reference-board
thermal capability command. Probe fails even though its legacy RPM and
thermistor queries work and firmware controls the fan automatically.

Select a read-only path for the Lenovo compatible. Expose its first RPM
channel and thermistor through hwmon, validating the transfer length and
RPM payload count and treating the thermistor's 0xff sentinel as ENODATA.
Do not enable SCI, register manual cooling controls or send standby
commands on this path. Keep the reference-board behavior and strict
capability validation unchanged.

The transactions are documented by the Yoga's FC22 and FC29/TZ39 DSDT
methods and Maya Matuszczyk's EC protocol notes. Anvesh Jain P's pending
fan-profile series also documents the RPM query. This change does not
include its calibration, LUT programming or temperature reporting.

Link: https://github.com/aarch64-laptops/build/blob/2e58842f5fa2f87771c2df017ae4d8c65225ef10/misc/lenovo-yoga-slim-7x/acpi/dsdt.dsl
Link: https://lkml.iu.edu/hypermail/linux/kernel/2607.3/08806.html
Signed-off-by: Birk Skyum <birk.skyum@xxxxx>
---
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/qcom-ec.rst | 40 +++++++

Platform drivers are not documented here. This directory is intended
for hardware moitoring drivers in the drivers/hwmon/ directory.

Guenter