From 7cd90ecd34cef1ddc5d2d87025eb4ce197014ddc Mon Sep 17 00:00:00 2001
From: Aaron Kling <webgeek1234@gmail.com>
Date: Tue, 15 Jul 2025 20:32:33 -0500
Subject: [PATCH] kernel: Support building from kernel platform

This expects a few build variables to be set:

* TARGET_KERNEL_PLATFORM_TARGET: The base target name. For example,
  'tegra' will indicate that the dist target is tegra_dist, abi is
  tegra_abi, etc.
* TARGET_KERNEL_VERSION: Used to determine the kernel checkout path. For
  example, a value of 6.6 will expect the kernel platform repo to be
  checked out to $BUILD_TOP/../kernel-6.6.
* TARGET_KERNEL_SOURCE: Relative to the top of the kernel platform
  checkout, the path to the kernel build rules. For example,
  vendor/nvidia/tegra.
* BOARD_KERNEL_IMAGE_NAME: The kernel image to use. For example, Image.

Using the examples above, this will run bazel in the kernel-6.6
directory on the target //vendor/nvidia/tegra:tegra_dist, then source
the output from $OUT/tegra/dist, with the prebuilt kernel image being
Image.

Change-Id: If96e96dffa2c0bfd9bd824bb3d8064eb861c9d00
---

diff --git a/build/soong/Android.bp b/build/soong/Android.bp
index 5dac859..6b27c94 100644
--- a/build/soong/Android.bp
+++ b/build/soong/Android.bp
@@ -21,7 +21,16 @@
     name: "generated_kernel_includes",
 
     // The headers make command
-    cmd: "$(PATH_OVERRIDE_SOONG) $(KERNEL_MAKE_CMD) $(KERNEL_MAKE_FLAGS) -C $(TARGET_KERNEL_SOURCE) O=$(KERNEL_BUILD_OUT_PREFIX)$(genDir) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) headers_install && vendor/lineage/tools/clean_headers.sh $(KERNEL_BUILD_OUT_PREFIX)$(genDir)",
+    cmd: "if [ -n \"$(TARGET_KERNEL_PLATFORM_TARGET)\" ]; then " +
+         "    pushd $(KERNEL_PATH); " +
+         "    ./tools/bazel --output_user_root=$(KERNEL_BUILD_OUT_PREFIX)$(genDir)/bazel-out run --experimental_convenience_symlinks=ignore --cpu=$(KERNEL_ARCH) //$(TARGET_KERNEL_SOURCE):$(TARGET_KERNEL_PLATFORM_TARGET)_uapi_headers_dist -- --destdir=$(KERNEL_BUILD_OUT_PREFIX)$(genDir); " +
+         "    popd; " +
+         "    gzip -d $(KERNEL_BUILD_OUT_PREFIX)$(genDir)/kernel-uapi-headers.tar.gz; " +
+         "    tar -xf $(KERNEL_BUILD_OUT_PREFIX)$(genDir)/kernel-uapi-headers.tar -C $(KERNEL_BUILD_OUT_PREFIX)$(genDir); " +
+         "else " +
+         "    $(PATH_OVERRIDE_SOONG) $(KERNEL_MAKE_CMD) $(KERNEL_MAKE_FLAGS) -C $(TARGET_KERNEL_SOURCE) O=$(KERNEL_BUILD_OUT_PREFIX)$(genDir) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) headers_install; " +
+         "fi; " +
+         "vendor/lineage/tools/clean_headers.sh $(KERNEL_BUILD_OUT_PREFIX)$(genDir)",
 
     // Directories that can be imported by a cc_* module generated_headers property
     export_include_dirs: [
diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index 6f7d92a..62b3dfa 100644
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -84,6 +84,9 @@
 #   TARGET_DTB_LIST_WILDCARD           = Optional, limits the .dtb files used to generate the
 #                                          final DTB image when NOT using QCOM's merge_dtbs
 #                                          script. Allows multiple patterns.
+#
+#   TARGET_KERNEL_PLATFORM_TARGET      = Optional, enables building an external kernel
+#                                          platform tree, this specifies the base target name
 
 ifneq ($(TARGET_NO_KERNEL),true)
 ifneq ($(TARGET_NO_KERNEL_OVERRIDE),true)
@@ -102,6 +105,7 @@
 TARGET_DTB_LIST_WILDCARD ?= *
 # recovery modules.load fallback - optional
 BOARD_RECOVERY_KERNEL_MODULES_LOAD ?= $(BOARD_RECOVERY_RAMDISK_KERNEL_MODULES_LOAD)
+TARGET_KERNEL_MIXED_MODE ?= true
 
 ## Internal variables
 DTC := $(HOST_OUT_EXECUTABLES)/dtc
@@ -153,7 +157,22 @@
                 $(eval HAS_PREBUILT_KERNEL := true)))
     endif
 
-    ifneq ($(HAS_PREBUILT_KERNEL),)
+    ifneq ($(TARGET_KERNEL_PLATFORM_TARGET),)
+        ifeq "$(wildcard $(abspath $(BUILD_TOP)/../kernel-$(TARGET_KERNEL_VERSION))/$(KERNEL_SRC) )" ""
+            $(warning ***************************************************************)
+            $(warning *                                                             *)
+            $(warning * No kernel platform source found.                            *)
+            $(warning * Please make sure your device is properly configured to      *)
+            $(warning * download the kernel repository to $(KERNEL_SRC))
+            $(warning *                                                             *)
+            $(warning ***************************************************************)
+            $(error "NO KERNEL")
+        endif
+        NEEDS_KERNEL_COPY := true
+        FULL_KERNEL_BUILD := false
+        TARGET_PREBUILT_INT_KERNEL := $(KERNEL_OUT)/$(BOARD_KERNEL_IMAGE_NAME)
+        KERNEL_BIN := $(TARGET_PREBUILT_INT_KERNEL)
+    else ifneq ($(HAS_PREBUILT_KERNEL),)
         ifeq ($(TARGET_PREBUILT_KERNEL_HEADERS),)
             $(warning ***************************************************************)
             $(warning * Using prebuilt kernel binary instead of source              *)
@@ -337,6 +356,10 @@
 $(call internal-make-kernel-target,$(DTB_OUT),$(1))
 endef
 
+endif # FULL_KERNEL_BUILD
+
+ifneq ($(filter $(FULL_KERNEL_BUILD),true)$(TARGET_KERNEL_PLATFORM_TARGET),)
+
 # $(1): modules list
 # $(2): output dir
 # $(3): mount point
@@ -390,9 +413,9 @@
     fi;
 endef
 
-endif # FULL_KERNEL_BUILD
+endif # FULL_KERNEL_BUILD or TARGET_KERNEL_PLATFORM_TARGET
 
-ifeq ($(FULL_KERNEL_BUILD),true)
+ifneq ($(filter $(FULL_KERNEL_BUILD),true)$(TARGET_KERNEL_PLATFORM_TARGET),)
 
 ifeq ($(NEED_KERNEL_MODULE_ROOT),true)
 KERNEL_MODULES_OUT := $(TARGET_ROOT_OUT)
@@ -431,7 +454,7 @@
 SYSTEM_KERNEL_MODULE_MOUNTPOINT := system_dlkm
 SYSTEM_KERNEL_MODULES_PARTITION_FILE_LIST := $(system_dlkmimage_intermediates)/file_list.txt
 $(INSTALLED_SYSTEM_DLKMIMAGE_TARGET): $(TARGET_PREBUILT_INT_KERNEL)
-else ifneq ($(SYSTEM_KERNEL_MODULES),)
+else ifneq ($(SYSTEM_KERNEL_MODULES)$(filter $(TARGET_KERNEL_MIXED_MODE),true),)
 SYSTEM_KERNEL_MODULES_OUT := $(TARGET_OUT)
 SYSTEM_KERNEL_DEPMOD_STAGING_DIR := $(KERNEL_BUILD_OUT_PREFIX)$(call intermediates-dir-for,PACKAGING,depmod_system)
 SYSTEM_KERNEL_MODULE_MOUNTPOINT := system
@@ -470,6 +493,10 @@
 $(recovery_uncompressed_ramdisk): $(TARGET_PREBUILT_INT_KERNEL)
 endif
 
+endif # TARGET_KERNEL_PLATFORM_TARGET or FULL_KERNEL_BUILD
+
+ifeq ($(FULL_KERNEL_BUILD),true)
+
 $(KERNEL_OUT):
 	mkdir -p $(KERNEL_OUT)
 
@@ -684,6 +711,27 @@
 
 endif # FULL_KERNEL_BUILD
 
+ifneq ($(TARGET_KERNEL_PLATFORM_TARGET),)
+KERNEL_PATH := $(abspath $(BUILD_TOP)/../kernel-$(TARGET_KERNEL_VERSION))
+$(TARGET_PREBUILT_INT_KERNEL): $(DEPMOD) $(KERNEL_MODULES_PARTITION_FILE_LIST) $(SYSTEM_KERNEL_MODULES_PARTITION_FILE_LIST)
+	@echo "Building $(BOARD_KERNEL_IMAGE_NAME)"
+	@mkdir -p $(KERNEL_OUT)
+	@rm -rf $(KERNEL_PATH)/out
+	$(hide) cd $(KERNEL_PATH) && ./tools/bazel --output_user_root=$(abspath $(KERNEL_OUT)/bazel-out) run --experimental_convenience_symlinks=ignore --cpu=$(KERNEL_ARCH) //$(KERNEL_SRC):$(TARGET_KERNEL_PLATFORM_TARGET)_dist -- --destdir=$(KERNEL_OUT)
+	$(if $(BOOT_KERNEL_MODULES),\
+		$(call build-image-kernel-modules-lineage,$(addprefix $(KERNEL_OUT)/,$(BOOT_KERNEL_MODULES)),$(KERNEL_VENDOR_RAMDISK_MODULES_OUT),,$(KERNEL_VENDOR_RAMDISK_DEPMOD_STAGING_DIR),$(KERNEL_VENDOR_RAMDISK_KERNEL_MODULES_LOAD),,,)\
+	)
+	$(if $(RECOVERY_KERNEL_MODULES),\
+		$(call build-image-kernel-modules-lineage,$(addprefix $(KERNEL_OUT)/,$(RECOVERY_KERNEL_MODULES)),$(KERNEL_RECOVERY_MODULES_OUT),,$(KERNEL_RECOVERY_DEPMOD_STAGING_DIR),$(BOARD_RECOVERY_KERNEL_MODULES_LOAD),,,)\
+	)
+	$(if $(filter $(TARGET_KERNEL_MIXED_MODE),true),\
+		system_dlkm_modules=$$(awk -F'/' '{ print "$(KERNEL_OUT)/"$$NF }' $(KERNEL_OUT)/system_dlkm.modules.load); \
+		($(call build-image-kernel-modules-lineage,$$system_dlkm_modules,$(SYSTEM_KERNEL_MODULES_OUT),$(SYSTEM_KERNEL_MODULE_MOUNTPOINT)/,$(SYSTEM_KERNEL_DEPMOD_STAGING_DIR),,,$(SYSTEM_KERNEL_MODULES_PARTITION_FILE_LIST),))\
+	)
+	vendor_modules=$$(comm -23 <(find $(KERNEL_OUT) -maxdepth 1 -type f -name '*.ko' | awk -F'/' '{ print $$NF }' | sort) <(awk -F'/' '{ print $$NF }' $(KERNEL_OUT)/system_dlkm.modules.load | sort) | sed 's|^|$(KERNEL_OUT)/|'); \
+	($(call build-image-kernel-modules-lineage,$$vendor_modules,$(KERNEL_MODULES_OUT),$(KERNEL_MODULE_MOUNTPOINT)/,$(KERNEL_DEPMOD_STAGING_DIR),$(BOARD_VENDOR_KERNEL_MODULES_LOAD),,$(KERNEL_MODULES_PARTITION_FILE_LIST),$(SYSTEM_KERNEL_DEPMOD_STAGING_DIR)/lib/modules/0.0/$(SYSTEM_KERNEL_MODULE_MOUNTPOINT)))
+endif
+
 ifeq ($(NEEDS_KERNEL_COPY),true)
 $(INSTALLED_KERNEL_TARGET): $(KERNEL_BIN)
 	$(transform-prebuilt-to-target)
diff --git a/config/BoardConfigKernel.mk b/config/BoardConfigKernel.mk
index 2c7b3d5..acb5b46 100644
--- a/config/BoardConfigKernel.mk
+++ b/config/BoardConfigKernel.mk
@@ -271,3 +271,7 @@
 ifeq ($(OUT_DIR_PREFIX),out)
     KERNEL_BUILD_OUT_PREFIX := $(BUILD_TOP)/
 endif
+
+ifneq ($(TARGET_KERNEL_PLATFORM_TARGET),)
+KERNEL_PATH := $(abspath $(BUILD_TOP)/../kernel-$(TARGET_KERNEL_VERSION))
+endif
diff --git a/config/BoardConfigSoong.mk b/config/BoardConfigSoong.mk
index d510717..cd65d4b 100644
--- a/config/BoardConfigSoong.mk
+++ b/config/BoardConfigSoong.mk
@@ -7,9 +7,11 @@
     KERNEL_CROSS_COMPILE \
     KERNEL_MAKE_CMD \
     KERNEL_MAKE_FLAGS \
+    KERNEL_PATH \
     PATH_OVERRIDE_SOONG \
     TARGET_KERNEL_CONFIG \
     TARGET_KERNEL_SOURCE \
+    TARGET_KERNEL_PLATFORM_TARGET \
     TARGET_PREBUILT_KERNEL_HEADERS
 
 # Setup SOONG_CONFIG_* vars to export the vars listed above.