Allow newer config versions to config older versions with the same

major number.

Reviewed by: ru@, jhb@, arch@ (a few months ago)

# this is subject to refinement based on experience.

2 files changed, 30 insertions, 21 deletions

diff --git a/usr.sbin/config/configvers.h b/usr.sbin/config/configvers.h
index 2a1a238..5ecac09 100644
--- a/usr.sbin/config/configvers.h
+++ b/usr.sbin/config/configvers.h
@@ -1,7 +1,15 @@
+/*-
+ * This file is in the public domain
+ *
+ * $FreeBSD$
+ */
+
 /*
- * 6 digits of version.  The most significant are branch indicators
- * (eg: RELENG_2_2 = 22, -current presently = 70 etc).  The least
- * significant digits are incremented as needed.
+ * 6 digits of version.  The most significant are branch indicators at the
+ * time when the last incompatible change was made (which is why it is
+ * presently 6 on 7-current).  The least significant digits are incremented
+ * as described below.  The format is similar to the __FreeBSD_version, but
+ * not tied to it.
  *
  * DO NOT CASUALLY BUMP THIS NUMBER!  The rules are not the same as shared
  * libs or param.h/osreldate.
@@ -21,25 +29,25 @@
  * compatable with the new buildkernel.  The buildtools phase and much more
  * comprehensive error code returns solved this original problem.
  *
- * Most end-users will use buildkenel and the build tools from buildworld.
+ * Most end-users will use buildkernel and the build tools from buildworld.
  * The people that are inconvenienced by gratuitous bumps are developers
- * who run config by hand. 
+ * who run config by hand.  However, developers shouldn't gratuitously be
+ * inconvenienced.
+ *
+ * One should bump the CONFIGVERS in the following ways:
+ *
+ * (1) If you change config such that it won't read old config files,
+ *     then bump the major number.  You shouldn't be doing this unless
+ *     you are overhauling config.  Do not casually bump this number
+ *     and by implication do not make changes that would force a bump
+ *     of this number casually.  You should limit major bumps to once
+ *     per branch.
+ * (2) For each new feature added, bump the minor version of this file.
+ *     When a new feature is actually used by the build system, update the
+ *     %VERSREQ field in the Makefile.$ARCH of all the affected makefiles
+ *     (typically all of them).
  *
  * $FreeBSD$
  */
 #define	CONFIGVERS	600004
-
-/*
- * Examples of when there should NOT be a bump:
- * - Adding a new keyword
- * - Changing the syntax of a keyword such that old syntax will break config.
- * - Changing the syntax of a keyword such that new syntax will break old
- *   config binaries.
- *
- * Examples of when there should be a bump:
- * - When files generated in sys/$mach/compile/NAME are changed and the
- *   Makefile.$mach rules might not handle it correctly.
- * - When there are incompatable changes to the way sys/conf/files.* or the
- *   other associated files are parsed such that they will be interpreted
- *   incorrectly rather than fail outright.
- */
+#define	MAJOR_VERS(x)	((x) / 100000)
diff --git a/usr.sbin/config/mkmakefile.c b/usr.sbin/config/mkmakefile.c
index 655d7e9..10e7ba8 100644
--- a/usr.sbin/config/mkmakefile.c
+++ b/usr.sbin/config/mkmakefile.c
@@ -153,7 +153,8 @@ makefile(void)
 			do_clean(ofp);
 		else if (strncmp(line, "%VERSREQ=", sizeof("%VERSREQ=") - 1) == 0) {
 			versreq = atoi(line + sizeof("%VERSREQ=") - 1);
-			if (versreq != CONFIGVERS) {
+			if (MAJOR_VERS(versreq) != MAJOR_VERS(CONFIGVERS) ||
+			    versreq > CONFIGVERS) {
 				fprintf(stderr, "ERROR: version of config(8) does not match kernel!\n");
 				fprintf(stderr, "config version = %d, ", CONFIGVERS);
 				fprintf(stderr, "version required = %d\n\n", versreq);