From d6ca5c9353413c5a61db9d6a3e1fe4b9365748e6 Mon Sep 17 00:00:00 2001
From: Daniel Schaefer <dhs@frame.work>
Date: Sun, 18 May 2025 20:09:32 +0800
Subject: [PATCH] Start documenting kernel support of EC

Signed-off-by: Daniel Schaefer <dhs@frame.work>
---
 kernel-support.md | 80 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 kernel-support.md

diff --git a/kernel-support.md b/kernel-support.md
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+# ChromeOS Kernel Modules
+
+Much of the functionality of `framework_tool` is to interact with the EC.
+On Linux there are kernel modules to do similar tasks
+
+## EC Version
+
+```
+> cat /sys/class/chromeos/cros_ec/version
+RO version:    lilac-3.0.3-413f018
+RW version:    lilac-3.0.3-413f018
+Firmware copy: RO
+Build info:    lilac-3.0.3-413f018 2025-03-06 05:45:28 marigold2@ip-172-26-3-226
+Chip vendor:   Nuvoton
+Chip name:     npcx9m3f
+Chip revision: 00160207
+Board version: 8
+```
+
+### Reboot EC
+
+```
+> cat /sys/class/chromeos/cros_ec/reboot
+ro|rw|cancel|cold|disable-jump|hibernate|cold-ap-off [at-shutdown]
+```
+
+## Sensors (Fan Speed) and Temperature
+
+```
+> cat /sys/class/chromeos/cros_ec/device/cros-ec-hwmon.8.auto/hwmon/hwmon13/temp*
+> sensors cros_ec-isa-0000
+cros_ec-isa-0000
+Adapter: ISA adapter
+fan1:               0 RPM
+local_f75303@4d:  +42.9°C
+cpu_f75303@4d:    +46.9°C
+ddr_f75303@4d:    +34.9°C
+cpu@4c:           +48.9°C
+
+> ls -l /sys/class/chromeos/cros_ec/device/cros-ec-hwmon.*.auto/hwmon/hwmon*/
+total 0
+lrwxrwxrwx 1 root root    0 May 18 13:47 device -> ../../../cros-ec-hwmon.8.auto/
+-r--r--r-- 1 root root 4096 May 18 13:47 fan1_fault
+-r--r--r-- 1 root root 4096 May 18 13:47 fan1_input
+-r--r--r-- 1 root root 4096 May 18 17:40 name
+drwxr-xr-x 2 root root    0 May 18 17:37 power/
+lrwxrwxrwx 1 root root    0 May 18 13:52 subsystem -> ../../../../../../../class/hwmon/
+-r--r--r-- 1 root root 4096 May 18 13:47 temp1_fault
+-r--r--r-- 1 root root 4096 May 18 17:42 temp1_input
+-r--r--r-- 1 root root 4096 May 18 17:42 temp1_label
+-r--r--r-- 1 root root 4096 May 18 13:47 temp2_fault
+-r--r--r-- 1 root root 4096 May 18 13:47 temp2_input
+-r--r--r-- 1 root root 4096 May 18 17:42 temp2_label
+-r--r--r-- 1 root root 4096 May 18 13:47 temp3_fault
+-r--r--r-- 1 root root 4096 May 18 13:47 temp3_input
+-r--r--r-- 1 root root 4096 May 18 17:42 temp3_label
+-r--r--r-- 1 root root 4096 May 18 13:47 temp4_fault
+-r--r--r-- 1 root root 4096 May 18 13:47 temp4_input
+-r--r--r-- 1 root root 4096 May 18 17:42 temp4_label
+-rw-r--r-- 1 root root 4096 May 18 13:52 uevent
+```
+
+## Keyboard backlight LEDs (Framework 12, Framework 13)
+
+Module: `leds_cros_ec`
+
+```
+# Check current brightness
+# This changes even if you adjust with fn+space
+> cat /sys/class/leds/chromeos::kbd_backlight/brightness
+0
+
+# Check max brightness
+> cat /sys/class/leds/chromeos::kbd_backlight/max_brightness
+100
+
+# Change brightness
+> echo 100 | sudo tee /sys/class/leds/chromeos::kbd_backlight/brightness
+100
+```