Add support for Lenovo Legion Slim 5 16AHP9 (NRCN) and fix legiond segfault

[Hashim-K]

Summary

This PR adds support for the Lenovo Legion Slim 5 16AHP9 (BIOS: NRCN) and fixes a critical segmentation fault in the legiond daemon caused by NULL pointer dereference when reading power supply status.

Changes

1. Add Legion Slim 5 16AHP9 Support

Commit: 46939a7
File: kernel_module/legion-laptop.c

Adds model_nrcn configuration for Legion Slim 5 16AHP9 (Model 83DH).

Hardware Details:

• Model: 83DH
• BIOS: NRCN17WW
• CPU: AMD Ryzen 7 8845HS
• EC Chip ID: 0x8227
• EC Version: 0x2a4

Features Verified Working:

• ✅ Temperature monitoring (CPU, GPU via WMI3)
• ✅ Fan speed monitoring (1900-3500+ RPM range observed)
• ✅ Automatic BIOS fan control
• ✅ Power mode switching (quiet/balanced/performance/balanced-performance)
• ✅ Toggle features (G-Sync, Overdrive, keyboard backlight)
• ✅ Fn+Q hardware button integration
• ✅ Platform profile support

Known Hardware Limitations:

• Manual fan control not supported (BIOS-locked by design on this model)
• Fan curve reading/writing not available
• These are expected hardware behaviors, not software issues

Closes: #218

2. Fix legiond Segmentation Fault

Commit: 66c1ba3
File: extra/service/legiond/modules/powerstate.c

Fixed NULL pointer dereference in get_powerstate() causing immediate daemon crash on startup.

Problem:
The function called fscanf() on NULL file pointers when AC power supply paths failed to open. This occurred when both /sys/class/power_supply/ADP0/online and /sys/class/power_supply/ACAD/online don't exist on the system.

Stack trace of crash:
Process legiond (PID 101198) dumped core
#0 0x00007fad7a4423fb __vfscanf_internal (libc.so.6 + 0x423fb)
#1 0x00007fad7a435d3f __isoc99_fscanf (libc.so.6 + 0x35d3f)
#2 0x0000000000401f86 get_powerstate (/usr/bin/legiond + 0x1f86)
#3 0x00000000004025eb timer_handler (/usr/bin/legiond + 0x25eb)

Solution:
// Added NULL check after fopen attempts
fp = fopen(ac_path, "r");
if (fp == NULL)
fp = fopen(ac_path_alt, "r");

+if (fp == NULL) {

printf("failed to open AC power status file\n");

return P_ERROR_AC;
+}

// Similar checks added for platform_profile path

[awsms]

Hi Hashim, and thanks for the patch!
Are you sure it’s a BIOS limitation regarding setting custom RPMs for the fans?
Could we reach out to Lenovo about it, or is this an intentional restriction that they won’t change?
I don’t know if this is also restricted on Windows, but for reference, I’ve had my fan replaced on this laptop (16AHP9) after a failure, so maybe it’s a known defect on their side?