linux-info.eclass: Rework get_version and fix output directory detection

get_version used to detect the output directory under /lib/modules if
KBUILD_OUTPUT wasn't explicitly set, but this broke when bug #662772 was
fixed. The code is still there but effectively does nothing as
OUTPUT_DIR is already used to set KV_OUT_DIR above.

Bug: https://bugs.gentoo.org/662772
Signed-off-by: James Le Cuirot <chewi@gentoo.org>

eclass/linux-info.eclass

@@ -485,8 +485,6 @@ get_version() {
 		die "${FUNCNAME}() called on non-Linux system, please fix the ebuild"
 	fi
 
-	local tmplocal
-
 	[[ -n ${SKIP_KERNEL_CHECK} ]] && return
 
 	# No need to execute this twice assuming KV_FULL is populated.
@@ -541,13 +539,6 @@ get_version() {
 		return 1
 	fi
 
-	# OK so now we know our sources directory, but they might be using
-	# KBUILD_OUTPUT, and we need this for .config and localversions-*
-	# so we better find it, eh?
-	#
-	# Do we pass KBUILD_OUTPUT on the CLI?
-	local OUTPUT_DIR=${KBUILD_OUTPUT}
-
 	# And contrary to existing functions, I feel we shouldn't trust the
 	# directory name to find version information as this seems insane.
 	# So we parse ${KERNEL_MAKEFILE}.
@@ -565,13 +556,35 @@ get_version() {
 		return 1
 	fi
 
-	[[ -d "${OUTPUT_DIR}" ]] && KV_OUT_DIR="${OUTPUT_DIR}"
-	if [[ -n "${KV_OUT_DIR}" ]]; then
+	# Assume there is no local version to begin with.
+	KV_FULL=${KV_MAJOR}.${KV_MINOR}.${KV_PATCH}${KV_EXTRA}
+
+	# There may be separate source and output directories. Has the user set
+	# KBUILD_OUTPUT? If not, automatically fall back to finding the most
+	# relevant output directory. If so, but it doesn't exist, don't fall back as
+	# that's probably undesirable.
+	if [[ -n ${KBUILD_OUTPUT} ]]; then
+		if [[ -d ${KBUILD_OUTPUT} ]]; then
+			KV_OUT_DIR=${KBUILD_OUTPUT}
+		else
+			die "KBUILD_OUTPUT is set to ${KBUILD_OUTPUT} but it doesn't exist"
+		fi
+	else
+		for KV_OUT_DIR in "${SYSROOT}" "${ROOT}" ""; do
+			# We cannot use the local version to find the output directory
+			# because that is where it is written to.
+			KV_OUT_DIR+="/lib/modules/${KV_FULL}/build"
+			[[ -d ${KV_OUT_DIR} ]] && break
+		done
+	fi
+
+	if [[ -d ${KV_OUT_DIR} ]]; then
 		qeinfo "Found kernel object directory:"
 		qeinfo "    ${KV_OUT_DIR}"
+	else
+		# Just use KV_DIR as a last resort.
+		KV_OUT_DIR=${KV_DIR}
 	fi
-	# and if we STILL have not got it, then we better just set it to KV_DIR
-	KV_OUT_DIR="${KV_OUT_DIR:-${KV_DIR}}"
 
 	# Grab the kernel release from the output directory.
 	# TODO: we MUST detect kernel.release being out of date, and 'return 1' from
@@ -585,7 +598,7 @@ get_version() {
 	fi
 
 	# KV_LOCAL currently contains the full release; discard the first bits.
-	tmplocal=${KV_LOCAL#${KV_MAJOR}.${KV_MINOR}.${KV_PATCH}${KV_EXTRA}}
+	local tmplocal=${KV_LOCAL#"${KV_FULL}"}
 
 	# If the updated local version was not changed, the tree is not prepared.
 	# Clear out KV_LOCAL in that case.
@@ -597,22 +610,8 @@ get_version() {
 		KV_LOCAL=${tmplocal}
 	fi
 
-	# and in newer versions, we can also pull LOCALVERSION if it is set.
-	# but before we do this, we need to find if we use a different object directory.
-	# This *WILL* break if the user is using localversions, but we assume it was
-	# caught before this if they are.
-	if [[ -z ${OUTPUT_DIR} ]] ; then
-		# Try to locate a kernel that is most relevant for us.
-		for OUTPUT_DIR in "${SYSROOT}" "${ROOT}" "" ; do
-			OUTPUT_DIR+="/lib/modules/${KV_MAJOR}.${KV_MINOR}.${KV_PATCH}${KV_EXTRA}${KV_LOCAL}/build"
-			if [[ -e ${OUTPUT_DIR} ]] ; then
-				break
-			fi
-		done
-	fi
-
-	# And we should set KV_FULL to the full expanded version
-	KV_FULL="${KV_MAJOR}.${KV_MINOR}.${KV_PATCH}${KV_EXTRA}${KV_LOCAL}"
+	# Append the local version now that we (maybe) have it.
+	KV_FULL+=${KV_LOCAL}
 
 	qeinfo "Found sources for kernel version:"
 	qeinfo "    ${KV_FULL}"