[U-Boot] [PATCH][RFC] Update U-Boot's build timestamp on every compile

[Peter Tyser]

Hi Kim,

> > Use the GNU 'date' command to auto-generate a new U-Boot
> > timestamp on every compile.
> > 
> > Signed-off-by: Peter Tyser <ptyser at xes-inc.com>
> > ---
> > I noticed that the build time of U-Boot was not updated on every
> > compile which occassionally threw me for a loop as to whether
> > a new U-Boot binary was programmed, etc.  This patch updates
> > a U_BOOT_DATE define on every compile which can then be used
> > in place of the multiple "__DATE__ - __TIME__" preprocessor
> > macros that are currently used.
> 
> this text probably belongs in the commit message above your SOB.  But I
> still don't understand why __TIME__ didn't work for you..can you
> elaborate?

__TIME__ and __DATE__ aren't ideal as they are only updated when the
file that contains them is recompiled.  For example, during the normal
modify/build/test cycle the version string remains the same for an 85xx
board as start.S would not be recompiled.  So any number of U-Boot
compilations can contain different code, but have the same build
time/version string.  eg when a board boots up and spits out:

U-Boot 1.3.4 (Aug  7 2008 - 12:32:20)

CPU:   8572E, Version: 1.0, (0x80e80010)
....

the code really may not have been compiled on Aug 7th, it could have
been compiled today, yesterday, etc.

It would be nice in my mind if every compile of U-Boot resulted in a new
build time string.  Thus you could easily determine which version is
programmed on a board during bootup, by looking at a binary on your host
computer using hexdump, etc.  The RFC/PATCH I submitted made this change
for the 85xx platform as an example - other uses of __TIME__ and
__DATE__ would be similarly updated in a formal patch.


Also, if a board used __TIME__/__DATE__ in more than one location, it
could be confusing as the times wouldn't be identical.  For example, if
the build time were printed in common/lcd.c, it would not be identical
to the time printed on the serial port since lcd.c was not compiled at
the same time as cpu/mpc8xx/start.S.

Best,
Peter