v4.19.13 snapshot.
diff --git a/lib/raid6/unroll.awk b/lib/raid6/unroll.awk
new file mode 100644
index 0000000..c6aa036
--- /dev/null
+++ b/lib/raid6/unroll.awk
@@ -0,0 +1,20 @@
+
+# This filter requires one command line option of form -vN=n
+# where n must be a decimal number.
+#
+# Repeat each input line containing $$ n times, replacing $$ with 0...n-1.
+# Replace each $# with n, and each $* with a single $.
+
+BEGIN {
+ n = N + 0
+}
+{
+ if (/\$\$/) { rep = n } else { rep = 1 }
+ for (i = 0; i < rep; ++i) {
+ tmp = $0
+ gsub(/\$\$/, i, tmp)
+ gsub(/\$\#/, n, tmp)
+ gsub(/\$\*/, "$", tmp)
+ print tmp
+ }
+}