Re: [PATCH] Kbuild: Avoid DTB rebuilds if source files are untouched

[Stephen Warren <swarren@wwwdotorg.org>]

On 04/15/2013 07:59 AM, Vineet Gupta wrote:
> On 04/13/2013 03:22 AM, Stephen Warren wrote:
>>
>> After installing the ARC toolchain (which was a bit painful to track
>> down and install...) 
> 
> Sorry about that - we have a buildroot based distro about to be pushed upstream -
> that would make it easier.
> 
>> I reproduced your exact problem. I believe the
>> patch below fixes it:
>>
>> diff --git a/arch/arc/boot/dts/Makefile b/arch/arc/boot/dts/Makefile
>> index 5776835..2f2cf23 100644
>> --- a/arch/arc/boot/dts/Makefile
>> +++ b/arch/arc/boot/dts/Makefile
>> @@ -8,6 +8,8 @@ endif
>>  obj-y   += $(builtindtb-y).dtb.o
>>  targets += $(builtindtb-y).dtb
>>
>> +.SECONDARY: $(obj)/$(builtindtb-y).dtb.S
>> +
>>  dtbs:  $(addprefix  $(obj)/, $(builtindtb-y).dtb)
>>
>>  clean-files := *.dtb
> 
> Indeed it does - I fell stupid why this didn't occur to me. But given that you
> have dealt with the dtb Makefile stuff alot more than I have :-) do you know why
> it was not working when put in Makefile.lib because I feel a few other arches also
> suffer from the same issue and would need similar fixes.

Searching in Google implies that .SECONDARY doesn't work with wildcards
(%.dtb.S for example), whereas .PRECIOUS does. Seems like perhaps a bug
in make to me, but who knows. Perhaps that's why?

> Anyhow, for the patch, I can manually add --author="you" but it'll still lack your
> SOB - you OK with that or do you want to send a formal patch.

Sure, you can either just say Suggested-by: for me, or apply my s-o-b below:

Signed-off-by: Stephen Warren <swarren@nvidia.com>