dist-kernel-utils.eclass: Introduce eclass for helper functions

Move some of the utility functions from kernel-install.eclass
into dist-kernel-utils.eclass, in order to permit using them without
having all kernel-install phases exported.  This will be used in order
to support rebuilding initramfs in sys-fs/zfs-kmod.

Since the eclasses are used only by dist-kernel project eclasses
and ebuilds, update the function prefix while moving them.

Signed-off-by: Michał Górny <mgorny@gentoo.org>

3 files changed, 108 insertions, 76 deletions

diff --git a/eclass/dist-kernel-utils.eclass b/eclass/dist-kernel-utils.eclass
new file mode 100644
index 000000000000..cf7165d89947
--- /dev/null
+++ b/eclass/dist-kernel-utils.eclass
@@ -0,0 +1,96 @@
+# Copyright 2020-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: dist-kernel-utils.eclass
+# @MAINTAINER:
+# Distribution Kernel Project <dist-kernel@gentoo.org>
+# @AUTHOR:
+# Michał Górny <mgorny@gentoo.org>
+# @SUPPORTED_EAPIS: 7
+# @BLURB: Utility functions related to Distribution Kernels
+# @DESCRIPTION:
+# This eclass provides various utility functions related to Distribution
+# Kernels.
+
+if [[ ! ${_DIST_KERNEL_UTILS} ]]; then
+
+case "${EAPI:-0}" in
+	0|1|2|3|4|5|6)
+		die "Unsupported EAPI=${EAPI:-0} (too old) for ${ECLASS}"
+		;;
+	7)
+		;;
+	*)
+		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
+		;;
+esac
+
+# @FUNCTION: dist-kernel_build_initramfs
+# @USAGE: <output> <version>
+# @DESCRIPTION:
+# Build an initramfs for the kernel.  <output> specifies the absolute
+# path where initramfs will be created, while <version> specifies
+# the kernel version, used to find modules.
+#
+# Note: while this function uses dracut at the moment, other initramfs
+# variants may be supported in the future.
+dist-kernel_build_initramfs() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -eq 2 ]] || die "${FUNCNAME}: invalid arguments"
+	local output=${1}
+	local version=${2}
+
+	ebegin "Building initramfs via dracut"
+	dracut --force "${output}" "${version}"
+	eend ${?} || die "Building initramfs failed"
+}
+
+# @FUNCTION: dist-kernel_get_image_path
+# @DESCRIPTION:
+# Get relative kernel image path specific to the current ${ARCH}.
+dist-kernel_get_image_path() {
+	case ${ARCH} in
+		amd64|x86)
+			echo arch/x86/boot/bzImage
+			;;
+		arm64)
+			echo arch/arm64/boot/Image.gz
+			;;
+		arm)
+			echo arch/arm/boot/zImage
+			;;
+		ppc64)
+			# ./ is required because of ${image_path%/*}
+			# substitutions in the code
+			echo ./vmlinux
+			;;
+		*)
+			die "${FUNCNAME}: unsupported ARCH=${ARCH}"
+			;;
+	esac
+}
+
+# @FUNCTION: dist-kernel_install_kernel
+# @USAGE: <version> <image> <system.map>
+# @DESCRIPTION:
+# Install kernel using installkernel tool.  <version> specifies
+# the kernel version, <image> full path to the image, <system.map>
+# full path to System.map.
+dist-kernel_install_kernel() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -eq 3 ]] || die "${FUNCNAME}: invalid arguments"
+	local version=${1}
+	local image=${2}
+	local map=${3}
+
+	ebegin "Installing the kernel via installkernel"
+	# note: .config is taken relatively to System.map;
+	# initrd relatively to bzImage
+	installkernel "${version}" "${image}" "${map}"
+	eend ${?} || die "Installing the kernel failed"
+}
+
+_DIST_KERNEL_UTILS=1
+fi
diff --git a/eclass/kernel-build.eclass b/eclass/kernel-build.eclass
index 99279ba58a99..249f038fa107 100644
--- a/eclass/kernel-build.eclass
+++ b/eclass/kernel-build.eclass
@@ -1,4 +1,4 @@
-# Copyright 2020 Gentoo Authors
+# Copyright 2020-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: kernel-build.eclass
@@ -117,7 +117,7 @@ kernel-build_src_test() {
 
 	local ver="${PV}${KV_LOCALVERSION}"
 	kernel-install_test "${ver}" \
-		"${WORKDIR}/build/$(kernel-install_get_image_path)" \
+		"${WORKDIR}/build/$(dist-kernel_get_image_path)" \
 		"${T}/lib/modules/${ver}"
 }
 
@@ -173,7 +173,7 @@ kernel-build_src_install() {
 	# install the kernel and files needed for module builds
 	insinto "/usr/src/linux-${ver}"
 	doins build/{System.map,Module.symvers}
-	local image_path=$(kernel-install_get_image_path)
+	local image_path=$(dist-kernel_get_image_path)
 	cp -p "build/${image_path}" "${ED}/usr/src/linux-${ver}/${image_path}" || die
 
 	# building modules fails with 'vmlinux has no symtab?' if stripped
diff --git a/eclass/kernel-install.eclass b/eclass/kernel-install.eclass
index e826626e13f2..3b4af9e51c07 100644
--- a/eclass/kernel-install.eclass
+++ b/eclass/kernel-install.eclass
@@ -1,4 +1,4 @@
-# Copyright 2020 Gentoo Authors
+# Copyright 2020-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: kernel-install.eclass
@@ -40,7 +40,7 @@ case "${EAPI:-0}" in
 		;;
 esac
 
-inherit mount-boot toolchain-funcs
+inherit dist-kernel-utils mount-boot toolchain-funcs
 
 SLOT="${PV}"
 IUSE="+initramfs test"
@@ -70,70 +70,6 @@ BDEPEND="
 		x86? ( app-emulation/qemu[qemu_softmmu_targets_i386] )
 	)"
 
-# @FUNCTION: kernel-install_build_initramfs
-# @USAGE: <output> <version>
-# @DESCRIPTION:
-# Build an initramfs for the kernel.  <output> specifies the absolute
-# path where initramfs will be created, while <version> specifies
-# the kernel version, used to find modules.
-kernel-install_build_initramfs() {
-	debug-print-function ${FUNCNAME} "${@}"
-
-	[[ ${#} -eq 2 ]] || die "${FUNCNAME}: invalid arguments"
-	local output=${1}
-	local version=${2}
-
-	ebegin "Building initramfs via dracut"
-	dracut --force "${output}" "${version}"
-	eend ${?} || die "Building initramfs failed"
-}
-
-# @FUNCTION: kernel-install_get_image_path
-# @DESCRIPTION:
-# Get relative kernel image path specific to the current ${ARCH}.
-kernel-install_get_image_path() {
-	case ${ARCH} in
-		amd64|x86)
-			echo arch/x86/boot/bzImage
-			;;
-		arm64)
-			echo arch/arm64/boot/Image.gz
-			;;
-		arm)
-			echo arch/arm/boot/zImage
-			;;
-		ppc64)
-			# ./ is required because of ${image_path%/*}
-			# substitutions in the code
-			echo ./vmlinux
-			;;
-		*)
-			die "${FUNCNAME}: unsupported ARCH=${ARCH}"
-			;;
-	esac
-}
-
-# @FUNCTION: kernel-install_install_kernel
-# @USAGE: <version> <image> <system.map>
-# @DESCRIPTION:
-# Install kernel using installkernel tool.  <version> specifies
-# the kernel version, <image> full path to the image, <system.map>
-# full path to System.map.
-kernel-install_install_kernel() {
-	debug-print-function ${FUNCNAME} "${@}"
-
-	[[ ${#} -eq 3 ]] || die "${FUNCNAME}: invalid arguments"
-	local version=${1}
-	local image=${2}
-	local map=${3}
-
-	ebegin "Installing the kernel via installkernel"
-	# note: .config is taken relatively to System.map;
-	# initrd relatively to bzImage
-	installkernel "${version}" "${image}" "${map}"
-	eend ${?} || die "Installing the kernel failed"
-}
-
 # @FUNCTION: kernel-install_update_symlink
 # @USAGE: <target> <version>
 # @DESCRIPTION:
@@ -406,16 +342,16 @@ kernel-install_pkg_postinst() {
 		mount-boot_pkg_preinst
 
 		local ver="${PV}${KV_LOCALVERSION}"
-		local image_path=$(kernel-install_get_image_path)
+		local image_path=$(dist-kernel_get_image_path)
 		if use initramfs; then
 			# putting it alongside kernel image as 'initrd' makes
 			# kernel-install happier
-			kernel-install_build_initramfs \
+			dist-kernel_build_initramfs \
 				"${EROOT}/usr/src/linux-${ver}/${image_path%/*}/initrd" \
 				"${ver}"
 		fi
 
-		kernel-install_install_kernel "${ver}" \
+		dist-kernel_install_kernel "${ver}" \
 			"${EROOT}/usr/src/linux-${ver}/${image_path}" \
 			"${EROOT}/usr/src/linux-${ver}/System.map"
 	fi
@@ -441,7 +377,7 @@ kernel-install_pkg_postrm() {
 
 	if [[ -z ${ROOT} ]] && use initramfs; then
 		local ver="${PV}${KV_LOCALVERSION}"
-		local image_path=$(kernel-install_get_image_path)
+		local image_path=$(dist-kernel_get_image_path)
 		ebegin "Removing initramfs"
 		rm -f "${EROOT}/usr/src/linux-${ver}/${image_path%/*}/initrd" &&
 			find "${EROOT}/usr/src/linux-${ver}" -depth -type d -empty -delete
@@ -458,16 +394,16 @@ kernel-install_pkg_config() {
 	mount-boot_pkg_preinst
 
 	local ver="${PV}${KV_LOCALVERSION}"
-	local image_path=$(kernel-install_get_image_path)
+	local image_path=$(dist-kernel_get_image_path)
 	if use initramfs; then
 		# putting it alongside kernel image as 'initrd' makes
 		# kernel-install happier
-		kernel-install_build_initramfs \
+		dist-kernel_build_initramfs \
 			"${EROOT}/usr/src/linux-${ver}/${image_path%/*}/initrd" \
 			"${ver}"
 	fi
 
-	kernel-install_install_kernel "${ver}" \
+	dist-kernel_install_kernel "${ver}" \
 		"${EROOT}/usr/src/linux-${ver}/${image_path}" \
 		"${EROOT}/usr/src/linux-${ver}/System.map"
 }