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

[Tom Rini]

On Wed, Aug 04, 2021 at 05:43:41PM -0400, 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 at 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 at 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 at 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)
> 
> 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.

Note that with this series applied, if you made use of
SOURCE_DATE_EPOCH, nothing would be rebuilt.  That may or may not make
sense however, in your case.  This series does get us closer to being
able to do what the linux kernel does as there's now just one place
rather than a bunch of places that are rebuilt.

-- 
Tom
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