kbuild/makefile: allow building host tools separately

Sometimes it is required to build only host U-Boot tools without building U-Boot itself for either board.

For example:
* In "buildroot" "uboot-tools" could be built for host just to have an ability to create uImage.
* Linux distributions ship "mkimage" utility as a separate substance.

This patch allows building host U-Boot tools separately from U-Boot itself and what is more important user only needs to have host compiler (gcc).

To build host tools just execute:
=====
make tools HOST_TOOLS_ONLY=yes
=====

Without this patch to generate tools user needs:
1. Configure any existing board with "make XXX_config"
2. Execute tools building but still cross-compiler will be invoked and if there's no proper cross-compiler in PATH compilation will fail.

---
 Kbuild   | 5 +++++
 Makefile | 7 +++++++
 2 files changed, 12 insertions(+)

index 1d89761..b5e348d 100644
@@ -4,6 +4,9 @@
 # 1) Generate generic-asm-offsets.h
 # 2) Generate asm-offsets.h
 
+# Don't execute target below if building host tools only
+ifneq ($(HOST_TOOLS_ONLY),yes)
+
 #####
 # 1) Generate generic-asm-offsets.h
 

@@ -85,3 +88,5 @@ $(CPUDIR)/$(SOC)/asm-offsets.s: $(CPUDIR)/$(SOC)/asm-offsets.c FORCE
 
 $(obj)/$(offsets-file): $(CPUDIR)/$(SOC)/asm-offsets.s
 	$(call cmd,offsets)
+
+endif

index b795338..2fb8ea1 100644
@@ -481,9 +481,12 @@ ifeq ($(dot-config),1)
 # load other configuration
 include $(srctree)/config.mk
 
+# Don't check for config.mk presence if building host tools only
+ifneq ($(HOST_TOOLS_ONLY),yes)
 ifeq ($(wildcard include/config.mk),)
 $(error "System not configured - see README")
 endif
+endif
 
 # If board code explicitly specified LDSCRIPT or CONFIG_SYS_LDSCRIPT, use
 # that (or fail if absent).  Otherwise, search for a linker script in a

@@ -994,10 +997,14 @@ ifeq ($(CONFIG_SYS_GENERIC_BOARD),y)
 	@/bin/false
 endif
 endif
+
+# Don't check for ldscript presence if building host tools only
+ifneq ($(HOST_TOOLS_ONLY),yes)
 ifeq ($(wildcard $(LDSCRIPT)),)
 	@echo >&2 "  Could not find linker script."
 	@/bin/false
 endif
+endif
 
 archprepare: prepare1 scripts_basic
 

1.8.5.3

Hi Alexey,

This may be the similar discussion to
http://u-boot.10912.n7.nabble.com/U-Boot-could-not-cross-compile-u-boot-tools-td174911.html
Providing a separate make target seems preferable.

Maybe like this?

To build host tools just execute:
=====
make tools-only
=====

And I am not happy about adding ifdef to everywhere.

So, how about a patch like this?

index c744718..12e1075 100644
@@ -409,7 +409,7 @@ timestamp_h := include/generated/timestamp_autogenerated.h
 
 no-dot-config-targets := clean clobber mrproper distclean \
                         help %docs check% coccicheck \
-                        ubootversion backup
+                        ubootversion backup tools-only
 
 config-targets := 0
 mixed-targets  := 0

@@ -1128,6 +1128,9 @@ checkarmreloc: u-boot
 env: scripts_basic
        $(Q)$(MAKE) $(build)=tools/$@
 
+tools-only: scripts_basic
+       $(Q)$(MAKE) $(build)=tools
+
 tools-all: export HOST_TOOLS_ALL=y
 tools-all: env tools ;
 

Best Regards
Masahiro Yamada

Hi Masahiro-san,

It looks not that relevant to me.
For example even before switching U-Boot to Kbuild it was not possible to build host tools simply without patching sources/headers or configuring real target. Or I might be missing something here.

Fully agree. I thought about it right after I sent you initial patch.

So do I. But I don't see other way around unfortunately.

$ make tools-only
  HOSTCC  scripts/basic/fixdep
  HOSTCC  tools/aisimage.o
  HOSTCC  tools/crc32.o
  HOSTCC  tools/default_image.o
  HOSTCC  tools/dumpimage.o
In file included from include/version.h:11:0,
                 from tools/dumpimage.c:11:
include/timestamp.h:11:47: fatal error:
generated/timestamp_autogenerated.h: No such file or directory
 #include "generated/timestamp_autogenerated.h"
                                               ^
compilation terminated.
make[1]: *** [tools/dumpimage.o] Error 1
make: *** [tools-only] Error 2
========

Hi Alexey,

Sorry, I should have explained it more exactly.

What I wanted you to refer is Wolfgang's comment in that thread.

This part:

And then we chose a new make target "cross_tools"
rather than a new option "CROSS_BUILD_TOOLS=1".

That is similar to what is happening here.

I wanted to show retionale why a make target "tools-only" is better than "HOST_TOOLS_ONLY=yes".

Oops - My bad.
I was disabling timestamp.

Could you fix like this?

tools-only: scripts_basic $(version_h) $(timestamp_h)

	$(Q)$(MAKE) $(build)=tools

It worked for me.

$ make  tools-only
  HOSTCC  scripts/basic/fixdep
  CHK     include/config/uboot.release
  UPD     include/config/uboot.release
  CHK     include/generated/version_autogenerated.h
  UPD     include/generated/version_autogenerated.h
  CHK     include/generated/timestamp_autogenerated.h
  UPD     include/generated/timestamp_autogenerated.h
  HOSTCC  tools/aisimage.o
  HOSTCC  tools/crc32.o
  HOSTCC  tools/default_image.o
  HOSTCC  tools/dumpimage.o
  HOSTCC  tools/fdt.o
  HOSTCC  tools/fdt_ro.o
  HOSTCC  tools/fdt_rw.o
  HOSTCC  tools/fdt_strerror.o
  HOSTCC  tools/fdt_wip.o
  HOSTCC  tools/fit_image.o
  HOSTCC  tools/image-fit.o
  HOSTCC  tools/image-host.o
  HOSTCC  tools/image.o
  HOSTCC  tools/imagetool.o
  HOSTCC  tools/imximage.o
  HOSTCC  tools/kwbimage.o
  HOSTCC  tools/md5.o
  HOSTCC  tools/mkenvimage.o
  HOSTCC  tools/mkimage.o
  HOSTCC  tools/mxsimage.o
  HOSTCC  tools/omapimage.o
  HOSTCC  tools/os_support.o
  HOSTCC  tools/pblimage.o
  HOSTCC  tools/sha1.o
  HOSTCC  tools/ublimage.o
  HOSTLD  tools/mkenvimage
  HOSTLD  tools/dumpimage
  HOSTLD  tools/mkimage
  HOSTCC  tools/proftool

Best Regards
Masahiro Yamada

Hi Masahiro-san,

Completely agree. I should have think a bit more before sending initial patch because right after the email was sent I thought why didn't I use a new target? :)

New target looks much better than some random variable. It's shorter and easier to use.

Works as a charm for me as well.
Do you mind to submit your changes (because it was you who implemented it properly and I don't want to "steal" your credits)?

Or I do it still on your behalf putting you in as an author?

-Alexey

Hi Alexey,

OK. I will post it with your Suggested-by credit.
Thanks for your kindness!

Best Regards
Masahiro Yamada