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OCLP Boot Fan Daemon — Integration Guide

Overview

This adds a LaunchDaemon that applies saved fan minimum RPM settings at boot, before the user logs in. This is critical for OCLP (OpenCore Legacy Patcher) Macs where the SMC fan controller defaults to maximum speed until software sets the minimum RPM.

Architecture

Boot → launchd loads com.smcfancontrol.bootdaemon.plist
     → runs /Library/Application Support/smcFanControl/smcfancontrold
     → detects OCLP (skips if not OCLP, unless forced)
     → reads /Library/Application Support/smcFanControl/fan-settings.plist
     → writes F{n}Mn keys to SMC
     → logs to /var/log/smcfancontrold.log
     → exits

Files

New files (daemon):

  • FanControlHelper/smcfancontrold.c — The daemon binary source
  • FanControlHelper/OCLPDetect.h — OCLP detection API (C header)
  • FanControlHelper/OCLPDetect.c — OCLP detection implementation
  • FanControlHelper/com.smcfancontrol.bootdaemon.plist — LaunchDaemon plist
  • FanControlHelper/fan-settings-example.plist — Example config
  • FanControlHelper/Makefile — Standalone build/install

New files (app integration):

  • Classes/OCLPHelper.h — Objective-C OCLP helper API
  • Classes/OCLPHelper.m — OCLP detection, daemon install/uninstall, settings sync

Modified files:

  • Classes/FanControl.m — Added OCLPHelper import, first-launch prompt, settings sync

Xcode Project Integration

1. Add a new target for smcfancontrold

  1. In Xcode, File → New → Target → macOS → Command Line Tool
  2. Name: smcfancontrold, Language: C
  3. Add these source files to the target:
    • FanControlHelper/smcfancontrold.c
    • FanControlHelper/OCLPDetect.c
    • FanControlHelper/OCLPDetect.h
  4. Link frameworks: IOKit.framework, CoreFoundation.framework
  5. Build Settings:
    • MACOSX_DEPLOYMENT_TARGET = 10.13
    • GCC_PREPROCESSOR_DEFINITIONS = (none needed, this is standalone)
  6. Under the main app target → Build Phases → Copy Bundle Resources:
    • Add the built smcfancontrold binary
    • Add com.smcfancontrol.bootdaemon.plist
  7. Add a "Target Dependency" from the main app to smcfancontrold

2. Add OCLPHelper to the main app target

  1. Add Classes/OCLPHelper.h and Classes/OCLPHelper.m to the smcFanControl target
  2. The #import "OCLPHelper.h" is already added to FanControl.m

3. Build and test

# Build daemon standalone
cd FanControlHelper
make

# Test OCLP detection (dry run)
sudo ./smcfancontrold -n

# Test with force flag (non-OCLP Mac)
sudo ./smcfancontrold -f -c fan-settings-example.plist

# Full install
sudo make install

How Settings Flow

  1. User adjusts fan slider in smcFanControl.app
  2. fanSliderChanged: writes to SMC and saves to NSUserDefaults
  3. [OCLPHelper syncFanSettingsWithDaemon] writes to system-level plist
  4. On next boot, smcfancontrold reads that plist and applies via SMC

OCLP Detection Methods

The daemon checks four indicators (any one is sufficient):

Method Check Reliability
Directory /Library/OpenCore exists High — OCLP always creates this
NVRAM opencore-version key present High — set by OpenCore bootloader
Directory /Library/Application Support/Dortania Medium — OCLP support files
Boot args amfi_get_out_of_my_way, revpatch=, etc. Medium — common OCLP flags

Daemon CLI Options

Usage: smcfancontrold [options]
  -c <path>   Config plist path (default: /Library/Application Support/smcFanControl/fan-settings.plist)
  -f          Force apply even if OCLP is not detected
  -n          Dry run (detect OCLP and read config, but don't write SMC)
  -q          Quiet mode (no log file, stderr only)
  -h          Show help

Security Notes

  • The daemon runs as root (required for SMC writes)
  • The LaunchDaemon plist must be owned by root:wheel with 644 permissions
  • The daemon binary must be owned by root:wheel with 755 permissions
  • Installation requires admin authentication (shown via standard macOS dialog)
  • The fan-settings.plist is readable by all but only writable with admin privileges