fix(cros-kernel2.eclass): Move kernel defconfig along side ebuilds

This makes it possible to have multiple kernel ebuilds in the tree at
once since the defconfig can be versioned along side the ebuilds instead
of being global.

sdk_container/src/third_party/coreos-overlay/eclass/cros-kernel2.eclass

@@ -21,17 +21,27 @@ STRIP_MASK="/usr/lib/debug/boot/vmlinux"
 : ${CROS_WORKON_INCREMENTAL_BUILD:=1}
 
 
-# If an overlay has eclass overrides, but doesn't actually override this
-# eclass, we'll have ECLASSDIR pointing to the active overlay's
-# eclass/ dir, but this eclass is still in the main chromiumos tree.  So
-# add a check to locate the cros-kernel/ regardless of what's going on.
-ECLASSDIR_LOCAL=${BASH_SOURCE[0]%/*}
-defconfig_dir() {
-        local d="${ECLASSDIR}/cros-kernel"
-        if [[ ! -d ${d} ]] ; then
-                d="${ECLASSDIR_LOCAL}/cros-kernel"
+# Search for an apropriate defconfig in ${FILESDIR}. The config should reflect
+# the kernel version but partial matching is allowed if the config is
+# applicalbe to multiple ebuilds, such as different -r revisions or stable
+# kernel releases. For an amd64 ebuild with version 3.12.4-r2 the order is:
+#  - x86_64_defconfig-3.12.4-r2
+#  - x86_64_defconfig-3.12.4
+#  - x86_64_defconfig-3.12
+#  - x86_64_defconfig
+# The first matching config is used, die otherwise.
+find_defconfig() {
+	local base_path="${FILESDIR}/$(tc-arch-kernel)_defconfig"
+	local try_suffix try_path
+	for try_suffix in "-${PVR}" "-${PV}" "-${PV%.*}" ""; do
+		try_path="${base_path}${try_suffix}"
+		if [[ -f "${try_path}" ]]; then
+			echo "${try_path}"
+			return
 		fi
-        echo "${d}"
+	done
+
+	die "No defconfig found for $(tc-arch-kernel) and ${PVR} in ${FILESDIR}"
 }
 
 # @FUNCTION: kernelversion
@@ -200,8 +210,7 @@ emit_its_script() {
 }
 
 kmake() {
-	# Allow override of kernel arch.
-	local kernel_arch=${CHROMEOS_KERNEL_ARCH:-$(tc-arch-kernel)}
+	local kernel_arch=$(tc-arch-kernel)
 
 	local cross=${CHOST}-
 	# Hack for using 64-bit kernel with 32-bit user-space
@@ -232,57 +241,17 @@ cros-kernel2_src_prepare() {
 }
 
 cros-kernel2_src_configure() {
-	# Use a single or split kernel config as specified in the board or variant
-	# make.conf overlay. Default to the arch specific split config if an
-	# overlay or variant does not set either CHROMEOS_KERNEL_CONFIG or
-	# CHROMEOS_KERNEL_SPLITCONFIG. CHROMEOS_KERNEL_CONFIG is set relative
-	# to the root of the kernel source tree.
-	local config
-	local cfgarch="$(get_build_arch)"
-
-	if [ -n "${CHROMEOS_KERNEL_CONFIG}" ]; then
-		config="${S}/${CHROMEOS_KERNEL_CONFIG}"
-	else
-		config=${CHROMEOS_KERNEL_SPLITCONFIG:-"chromiumos-${cfgarch}"}
-	fi
+	local config="$(find_defconfig)"
 
 	elog "Using kernel config: ${config}"
-
-	# Keep a handle on the old .config in case it hasn't changed.  This way
-	# we can keep the old timestamp which will avoid regenerating stuff that
-	# hasn't actually changed.
-	local temp_config="${T}/old-kernel-config"
-	if [[ -e $(get_build_cfg) ]] ; then
-		cp -a "$(get_build_cfg)" "${temp_config}"
-	else
-		rm -f "${temp_config}"
-	fi
-
-	if [ -n "${CHROMEOS_KERNEL_CONFIG}" ]; then
 	cp -f "${config}" "$(get_build_cfg)" || die
-	else
-		if [ -e chromeos/scripts/prepareconfig ] ; then
-			chromeos/scripts/prepareconfig ${config} \
-				"$(get_build_cfg)" || die
-		else
-			config="$(defconfig_dir)/${cfgarch}_defconfig"
-			ewarn "Can't prepareconfig, falling back to default " \
-				"${config}"
-			cp "${config}" "$(get_build_cfg)" || die
-		fi
-	fi
 
 	# copy the cpio initrd to the output build directory so we can tack it
 	# onto the kernel image itself.
 	cp "${ROOT}"/usr/share/bootengine/bootengine.cpio "$(cros-workon_get_build_dir)" || die "copy of dracut cpio failed."
 
-	# Use default for any options not explitly set in splitconfig
+	# Use default for any options not explitly set in defconfig
 	yes "" | kmake oldconfig
-
-	# Restore the old config if it is unchanged.
-	if cmp -s "$(get_build_cfg)" "${temp_config}" ; then
-		touch -r "${temp_config}" "$(get_build_cfg)"
-	fi
 }
 
 # @FUNCTION: get_dtb_name
@@ -353,7 +322,6 @@ cros-kernel2_src_compile() {
 	fi
 
 	local src_dir="$(cros-workon_get_build_dir)/source"
-	local kernel_arch=${CHROMEOS_KERNEL_ARCH:-$(tc-arch-kernel)}
 	SMATCH_ERROR_FILE="${src_dir}/chromeos/check/smatch_errors.log"
 
 	if use test && [[ -e "${SMATCH_ERROR_FILE}" ]]; then