kernel: allow target configs to be multiple files again

Clean up kernel configs again, hopefully this one will stick. Avoids
the need for "realpath" calls in the Makefile (since the merge tool
should be the one handling it), records the sources used to build the
config (instead of copying them around), and makes the source and output
variables easier to read.

Change-Id: Ie2b6fc222077b20f8b8f931c4c3084c6e692b38e

2 files changed, 46 insertions, 51 deletions

diff --git a/kernel.mk b/kernel.mk
index 294def8..e5511d9 100644
--- a/kernel.mk
+++ b/kernel.mk
@@ -23,7 +23,7 @@
 #
 # The following maybe set:
 # TARGET_KERNEL_CROSS_COMPILE_PREFIX to override toolchain.
-# TARGET_KERNEL_CONFIGS to specify a set of additional kernel configs.
+# TARGET_KERNEL_CONFIGS to specify a set of additional kernel config files.
 # TARGET_KERNEL_DTB to define a DTB to build.
 # TARGET_KERNEL_DTB_APPEND to append the built DTB to the kernel.
 
@@ -45,11 +45,6 @@ ifeq ($(TARGET_KERNEL_ARCH),)
 $(error TARGET_KERNEL_ARCH not defined)
 endif
 
-# This is optional, but we'd like to use it as a dependency.
-ifndef TARGET_KERNEL_CONFIGS
-TARGET_KERNEL_CONFIGS := /dev/null
-endif
-
 # Check target arch.
 KERNEL_TOOLCHAIN_ABS := $(realpath $(TARGET_TOOLCHAIN_ROOT)/bin)
 TARGET_KERNEL_ARCH := $(strip $(TARGET_KERNEL_ARCH))
@@ -111,25 +106,26 @@ endif
 
 # Set the output for the kernel build products.
 KERNEL_OUT := $(TARGET_OUT_INTERMEDIATES)/KERNEL_OBJ
-
-# The kernel configs, in precedence order.
-KERNEL_CONFIG_DEFAULT := $(KERNEL_OUT)/.config.default
-KERNEL_CONFIG_RECOMMENDED := $(KERNEL_OUT)/.config.recommended
-KERNEL_CONFIG_PRODUCT := $(KERNEL_OUT)/.config.product
-KERNEL_CONFIG_REQUIRED := $(KERNEL_OUT)/.config.required
-KERNEL_CONFIG := $(KERNEL_OUT)/.config
-
 KERNEL_BIN := $(KERNEL_OUT)/arch/$(KERNEL_SRC_ARCH)/boot/$(KERNEL_NAME)
 
 # Figure out which kernel version is being built (disregard -stable version).
 KERNEL_VERSION := $(shell $(MAKE) --no-print-directory -C $(TARGET_KERNEL_SRC) -s SUBLEVEL="" kernelversion)
 
-KERNEL_CONFIGS_DIR := device/generic/brillo/kconfig
-KERNEL_CONFIGS_COMMON := $(KERNEL_CONFIGS_DIR)/common.config
-KERNEL_CONFIGS_ARCH := $(KERNEL_CONFIGS_DIR)/$(KERNEL_ARCH).config
-KERNEL_CONFIGS_VER := $(KERNEL_CONFIGS_DIR)/$(KERNEL_VERSION)/common.config
-KERNEL_CONFIGS_VER_ARCH := $(KERNEL_CONFIGS_DIR)/$(KERNEL_VERSION)/$(KERNEL_ARCH).config
-KERNEL_CONFIGS_RECOMMENDED := $(KERNEL_CONFIGS_DIR)/recommended.config
+# Brillo kernel config file sources.
+KERNEL_CONFIG_DIR := device/generic/brillo/kconfig
+KERNEL_CONFIG_DEFAULT := $(TARGET_KERNEL_SRC)/arch/$(KERNEL_SRC_ARCH)/configs/$(TARGET_KERNEL_DEFCONFIG)
+KERNEL_CONFIG_RECOMMENDED := $(KERNEL_CONFIG_DIR)/recommended.config
+KERNEL_CONFIG_REQUIRED_SRC := \
+	$(KERNEL_CONFIG_DIR)/common.config \
+	$(KERNEL_CONFIG_DIR)/$(KERNEL_ARCH).config \
+	$(KERNEL_CONFIG_DIR)/$(KERNEL_VERSION)/common.config \
+	$(KERNEL_CONFIG_DIR)/$(KERNEL_VERSION)/$(KERNEL_ARCH).config
+KERNEL_CONFIG_REQUIRED := $(KERNEL_OUT)/.config.required
+KERNEL_CONFIG_SRC := $(KERNEL_CONFIG_DEFAULT) \
+		     $(KERNEL_CONFIG_RECOMMENDED) \
+		     $(TARGET_KERNEL_CONFIGS) \
+		     $(KERNEL_CONFIG_REQUIRED)
+KERNEL_CONFIG := $(KERNEL_OUT)/.config
 
 KERNEL_MERGE_CONFIG := device/generic/brillo/mergeconfig.sh
 KERNEL_HEADERS_INSTALL := $(KERNEL_OUT)/usr
@@ -137,32 +133,16 @@ KERNEL_HEADERS_INSTALL := $(KERNEL_OUT)/usr
 $(KERNEL_OUT):
 	mkdir -p $(KERNEL_OUT)
 
-$(KERNEL_CONFIG_DEFAULT): $(TARGET_KERNEL_SRC)/arch/$(KERNEL_SRC_ARCH)/configs/$(TARGET_KERNEL_DEFCONFIG) | $(KERNEL_OUT)
-	$(hide) cat $< > $@
-
-$(KERNEL_CONFIG_RECOMMENDED): $(KERNEL_CONFIGS_RECOMMENDED) | $(KERNEL_OUT)
-	$(hide) cat $< > $@
-
-$(KERNEL_CONFIG_PRODUCT): $(TARGET_KERNEL_CONFIGS) | $(KERNEL_OUT)
-	$(hide) cat $< > $@
-
-# Merge the required kernel config elements.
-$(KERNEL_CONFIG_REQUIRED): $(KERNEL_CONFIGS_COMMON) $(KERNEL_CONFIGS_ARCH) \
-			   $(KERNEL_CONFIGS_VER) $(KERNEL_CONFIGS_VER_ARCH) \
-			   | $(KERNEL_OUT)
-	$(hide) cat $(filter-out $(KERNEL_OUT),$^) > $@
+# Merge the required kernel config elements into a single file.
+$(KERNEL_CONFIG_REQUIRED): $(KERNEL_CONFIG_REQUIRED_SRC) | $(KERNEL_OUT)
+	$(hide) cat $^ > $@
 
 # Merge the final target kernel config.
-$(KERNEL_CONFIG): $(KERNEL_CONFIG_DEFAULT) $(KERNEL_CONFIG_RECOMMENDED) \
-		  $(KERNEL_CONFIG_PRODUCT) $(KERNEL_CONFIG_REQUIRED) \
-		  | $(KERNEL_OUT)
+$(KERNEL_CONFIG): $(KERNEL_CONFIG_SRC) | $(KERNEL_OUT)
 	$(hide) echo Merging kernel config
 	$(KERNEL_MERGE_CONFIG) $(TARGET_KERNEL_SRC) $(realpath $(KERNEL_OUT)) \
 		$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) \
-		$(realpath $(KERNEL_CONFIG_DEFAULT)) \
-		$(realpath $(KERNEL_CONFIG_RECOMMENDED)) \
-		$(realpath $(KERNEL_CONFIG_PRODUCT)) \
-		$(realpath $(KERNEL_CONFIG_REQUIRED))
+		$^
 
 # Disable CCACHE_DIRECT so that header location changes are noticed.
 define build_kernel
diff --git a/mergeconfig.sh b/mergeconfig.sh
index 0bdfed2..faa27b7 100755
--- a/mergeconfig.sh
+++ b/mergeconfig.sh
@@ -15,18 +15,33 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-array=( "$@" )
+args=( "$@" )
+confs=( )
 
-KERNEL_PATH=${array[0]}
-OUTPUT=${array[1]}
-TARGET_ARCH=${array[2]}
-TARGET_CROSS_COMPILE=${array[3]}
+KERNEL_PATH=${args[0]}
+OUTPUT=${args[1]}
+TARGET_ARCH=${args[2]}
+TARGET_CROSS_COMPILE=${args[3]}
 
-unset "array[0]"
-unset "array[1]"
-unset "array[2]"
-unset "array[3]"
+unset "args[0]"
+unset "args[1]"
+unset "args[2]"
+unset "args[3]"
+
+curdir=$(pwd)
+
+# Explicitly record the list of config files used to build .config, and
+# canonicalize the path since we have to have our current directory in
+# the kernel source tree.
+for conf in ${args[*]} ; do
+	fullpath=$conf
+	if [ ${fullpath:0:1} != "/" ] ; then
+		fullpath=$curdir/$fullpath
+	fi
+	confs+=($fullpath)
+	echo $conf
+done > $OUTPUT/config.list
 
 cd $KERNEL_PATH
 
-ARCH=$TARGET_ARCH CROSS_COMPILE=$TARGET_CROSS_COMPILE ./scripts/kconfig/merge_config.sh -O $OUTPUT ${array[*]}
+ARCH=$TARGET_ARCH CROSS_COMPILE=$TARGET_CROSS_COMPILE ./scripts/kconfig/merge_config.sh -O $OUTPUT ${confs[*]}