Re: [PATCH 11/11] Remove including timestamp.h in version.h

Pali Rohár
2021-08-04T21:53:07Z

On Wednesday 04 August 2021 17:43:41 Sean Anderson wrote:
> On 8/2/21 3:21 PM, Simon Glass wrote:
> > Hi Pali,
> >
> > On Mon, 2 Aug 2021 at 07:20, Pali Rohár <pali@kernel.org> wrote:
> > >
> > > Header file version.h does not use anything from timestamp.h. Including of
> > > timestamp.h has side effect which cause recompiling object file at every
> > > make run because timestamp.h changes at every run.
> > >
> > > So remove timestamp.h from version.h and include timestamp.h in files
> > > which needs it.
> > >
> > > This change reduce recompilation time of final U-Boot binary when U-Boot
> > > source files were not changed as less source files needs to be recompiled.
> > >
> > > Signed-off-by: Pali Rohár <pali@kernel.org>
> > > ---
> > > arch/arm/mach-rockchip/tpl.c | 4 ++++
> > > board/work-microwave/work_92105/work_92105_display.c | 1 +
> > > cmd/version.c | 1 +
> > > common/spl/spl.c | 4 ++++
> > > drivers/rtc/emul_rtc.c | 2 +-
> > > include/version.h | 2 --
> > > 6 files changed, 11 insertions(+), 3 deletions(-)
> >
> > Reviewed-by: Simon Glass <sjg@chromium.org>
> >
> > I assume we do actually want to regenerate the timestamp when U-Boot
> > builds, even if nothing has changed. Is that right?
>
> I know this is the current behavior, but it would be nice if this was
> not the case. If one is building U-Boot as part of a larger project, one
> might want to have a makefile rule like
>
> u-boot/u-boot.bin:
> $(MAKE) -C u-boot $(@F)

You are missing 'FORCE' prerequisite for u-boot/u-boot.bin target (but I
understand what you mean; I'm using this stuff too).

> but u-boot/u-boot.bin will always be remade even if no changes have been
> done. This will cause make to remake all dependents of U-Boot as well
> (which can be rather time-consuming).
>
> At the moment, I just use U-Boot as an order-only dependency and remake
> it manually. But I would love it if U-Boot was only remade if
> dependencies had actually changed, since this would make it easier to
> integrate it with the rest of my build system.

This behavior which you described is e.g. used by Linux kernel build
system (also based on Makefile(s) and Kbuild as U-Boot).

Maybe we can discuss if such change can or cannot be useful for U-Boot
too. But to not make another confusion, it is not part and it is not
related to this my patch series. So I would suggest to discuss about it
in separate / new thread (fell free to CC me).