gryphon-led-module: Build against bcmkernel on Broadcom platforms

Due to the complexity of the Broadcom build system which amongst others
puts dynamically generated symlinks into the kernel dir, we have a fake
kernel "bcmlinux" to please the OpenWrt build system. This kernel is not
used for anything but building the OpenWrt toolchain. To compile against
the right kernel that is running on the target, we need to compile the
kernel module against the kernel inside bcmkernel which is the one
compiled by the BCM SDK.

gryphon-led-module/Makefile

@@ -28,6 +28,7 @@ define KernelPackage/$(PKG_NAME)
   FILES:=$(PKG_BUILD_DIR)/$(PKG_NAME).$(LINUX_KMOD_SUFFIX)
   KCONFIG:=CONFIG_PACKAGE_kmod-gryphon-led-kernel-module=y
   AUTOLOAD:=$(call AutoLoad,60,$(PKG_NAME))
+  DEPENDS:= +(TARGET_iopsys_brcm63xx_arm):bcmkernel
   PKG_LICENSE:=GPLv2
   PKG_LICENSE_URL:=
 endef
@@ -40,6 +41,21 @@ EXTRA_KCONFIG:= CONFIG_RGB_LED=m
 
 MODULE_INCLUDE=-I$(PKG_BUILD_DIR)
 
+
+ifeq ($(CONFIG_TARGET_iopsys_brcm63xx_arm),y)
+	LINUX_DIR:=$(BUILD_DIR)/bcmkernel/bcm963xx/kernel/linux-4.19
+	MODULES_SUBDIR:=lib/modules/4.19.183
+	KERNEL_CROSS:=$(CONFIG_BCM_TOOLCHAIN)/bin/$(CONFIG_BCM_TOOLTUPLE)
+
+	ifeq ($(CONFIG_BCM_CHIP_ID),$(filter $(CONFIG_BCM_CHIP_ID),"63158" "6856" "6858"))
+		# These targets use a 64-bit kernel
+		LINUX_KARCH:=arm64
+		KERNEL_CROSS:=/opt/toolchains/crosstools-aarch64-gcc-9.2-linux-4.19-glibc-2.30-binutils-2.32/bin/aarch64-buildroot-linux-gnu-
+	endif
+	# For some reason, Broadcom's kernel does not set the include paths correctly when compiling out-of-tree modules
+	EXTRA_KCPPFLAGS:="-I $(LINUX_DIR)/../bcmkernel/include -I $(LINUX_DIR)/arch/arm/mach-bcm963xx/include"
+endif
+
 define Build/Prepare
 	mkdir -p $(PKG_BUILD_DIR)/kdevlinks/
 	$(CP) -s `pwd`/src/* $(PKG_BUILD_DIR)/kdevlinks/