Avoid breaking backlight on latops with AMD GPUs

Changelog.md

@@ -1,9 +1,9 @@
 WhateverGreen Changelog
 =======================
 #### v1.2.6
-- Added `-applbkloff` boot argument to termporarily disable `AppleBacklight` patching code
+- Added `applbkl=0` boot argument to termporarily disable `AppleBacklight` patching code
 - Fixed AMD Verde CAIL injection logic
-- Fixed breaking backlight on Apple hardware and on 10.11 or earlier
+- Fixed breaking backlight on Apple hardware, on laptops with AMD GPUs, and on 10.11 or earlier
 - Changed CFL backlight patches to enable by default on CFL drivers only (avoids issues with faux "KBL" 8xxx CPUs)
 
 #### v1.2.5

README.md

@@ -52,6 +52,7 @@ Read [FAQs](https://github.com/acidanthera/WhateverGreen/blob/master/Manual/) an
 - `-igfxdump` to dump IGPU framebuffer kext to `/AppleIntelFramebuffer_X_Y` (available in DEBUG binaries). 
 - `-igfxfbdump` to dump native and patched framebuffer table to ioreg at IOService:/IOResources/WhateverGreen
 - `igfxcflbklt=1` boot argument (and `enable-cfl-backlight-fix` property) to enable CFL backlight patch
+- `applbkl=0` boot argument to disable AppleBacklight.kext patches for IGPU
 
 #### Credits
 - [Apple](https://www.apple.com) for macOS

WhateverGreen/kern_weg.cpp

@@ -79,7 +79,8 @@ void WEG::init() {
 		lilu.onKextLoad(&kextAGDPolicy);
 
 	// Disable backlight patches if asked specifically.
-	if (!checkKernelArgument("-applbkloff"))
+	PE_parse_boot_argn("applbkl", &appleBacklightPatch, sizeof(appleBacklightPatch));
+	if (appleBacklightPatch != APPLBKL_OFF)
 		lilu.onKextLoad(&kextBacklight);
 
 	igfx.init();
@@ -164,7 +165,13 @@ void WEG::processKernel(KernelPatcher &patcher) {
 					resetFramebuffer = FB_COPY;
 			}
 
+			// Note, disabled Optimus will make videoExternal 0, so this case checks for active IGPU only.
 			size_t extNum = devInfo->videoExternal.size();
+			if (appleBacklightPatch == APPLBKL_DETECT && (devInfo->videoBuiltin == nullptr || extNum > 0)) {
+				// Either a builtin IGPU is not available, or some external GPU is available.
+				kextBacklight.switchOff();
+			}
+
 			for (size_t i = 0; i < extNum; i++) {
 				auto &v = devInfo->videoExternal[i];
 				processExternalProperties(v.video, devInfo, v.vendor);
@@ -179,8 +186,8 @@ void WEG::processKernel(KernelPatcher &patcher) {
 
 			if (devInfo->managementEngine)
 				processManagementEngineProperties(devInfo->managementEngine);
-		} else {
-			// Do not patch AppleBacklight on Apple HW!
+		} else if (appleBacklightPatch != APPLBKL_ON){
+			// Do not patch AppleBacklight on Apple HW, unless forced.
 			kextBacklight.switchOff();
 		}
 

WhateverGreen/kern_weg.hpp

@@ -76,6 +76,22 @@ class WEG {
 	 */
 	uint32_t resetFramebuffer {FB_DETECT};
 
+	/**
+	 *  APPLBKL_OFF     disables AppleBacklight patches.
+	 *  APPLBKL_ON      enforces AppleBacklight patches.
+	 *  APPLBKL_DETECT  enables AppleBacklight patches for IGPU-only non-Apple setups.
+	 */
+	enum BacklightPatchMode {
+		APPLBKL_OFF    = 0,
+		APPLBKL_ON     = 1,
+		APPLBKL_DETECT = 2
+	};
+
+	/**
+	 *  applbkkl boot-arg controlled AppleBacklight kext patch
+	 */
+	uint32_t appleBacklightPatch {APPLBKL_DETECT};
+
 	/**
 	 *  Console info structure, taken from osfmk/console/video_console.h
 	 *  Last updated from XNU 4570.1.46.