[U-Boot] [PATCH] ppc4xx: Enable support for 64bit printf on all PPC4xx variants

Scott Wood
2009-07-08T21:29:18Z

Wolfgang Denk wrote:
> Dear Scott Wood,
>
> In message <4A550B66.1090506@freescale.com> you wrote:
>> Note that the overhead of 64-bit printf (assuming the 64-bit
>> divide/remainder functions in libgcc aren't pulled in for anything else)
>> is 2524 bytes on powerpc (using GCC 4.3.2). That's less than NFS,
>> which gets turned on by default (as was brought up recently). :-)
>
> But compare the functionality...

I use 64-bit prints from time to time. I've never used NFS in u-boot.

More relevantly, it's obvious if NFS is missing -- it says "Unknown
command". It's not always obvious whether (or why) the printf output
you're looking at has been corrupted by an incomplete implementation.

>> What if we were to invert the option (CONFIG_SYS_NO_64BIT_VSPRINTF) so
>> that it would only be disabled on boards at the intersection of tight
>> space constraints and a board maintainer who's pretty sure this board
>> doesn't need it? There could also be some warning from printf() if %ll
>> is used when not supported, and/or it could still check for %ll and pop
>> a long long from the varargs but discard the high half.
>
> And by default we would add CONFIG_SYS_NO_64BIT_VSPRINTF to all board
> config files?

No, that's the point -- it would require the board maintainer to
explicitly say "this board doesn't need this". By default we would
provide a correct printf.

-Scott