[PATCH] build: allow a downstream suffix in the version shown during boot

[Nicolas Boulenguez <nicolas@debian.org>]

Hello.

https://lists.denx.de/pipermail/u-boot/2022-February/474887.html got
no answer, probably because it is trivial and has been lost among more
important topics, so I am submitting it again.

It is convenient for redistributors to add a build number to the
U-boot source version, which is displayed at boot and useful to know
if a device has been successfully updated, to triage bugs and so on.

For example, Debian adds '+dfsg-N' where N changes with each release
of a .deb package.

Author: Vagrant Cascadian <vagrant@debian.org>
Author: Nicolas Boulenguez <nicolas@debian.org>
Signed-By: Nicolas Boulenguez <nicolas@debian.org>

--- a/Makefile
+++ b/Makefile
@@ -456,7 +456,7 @@ KBUILD_AFLAGS	+= $(call cc-option,-fno-PIE)
 
 # Read UBOOTRELEASE from include/config/uboot.release (if it exists)
 UBOOTRELEASE = $(shell cat include/config/uboot.release 2> /dev/null)
-UBOOTVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
+UBOOTVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)$(BUILD_VERSION)
 
 export VERSION PATCHLEVEL SUBLEVEL UBOOTRELEASE UBOOTVERSION
 export ARCH CPU BOARD VENDOR SOC CPUDIR BOARDDIR
--- a/doc/build/gcc.rst
+++ b/doc/build/gcc.rst
@@ -151,6 +151,11 @@
 Note that the :doc:`tools` are always built with the included version of libfdt
 so it is not possible to build U-Boot tools with a system libfdt, at present.
 
+If you are modifying the upstream sources, please make this visible
+at boot time by defining the BUILD_VERSION version suffix.
+
+* BUILD_VERSION=+<vendor><build number><...>
+
 Other build targets
 ~~~~~~~~~~~~~~~~~~~