[yocto] Magic kernel config option.

[Brian Smucker]

On 1/2/2013 10:06 AM, Bruce Ashfield wrote:
 > On 12-12-24 02:59 PM, Brian Smucker wrote:
 >> Hi,
 >>
 >
 > Catching up on email from the holidays. Did you ever get an answer
 > to this ?
Not yet,  resumed my quest today.

 >> I'm a yocto mostly-newbie, trying to find my way.  I have a custom layer
 >> that I am using to build a kernel. The layer right now consists of a few
 >> kernel patches and a defconfig and is based on the standard kernel
 >> otherwise.
 >>
 >> When I do a diff on my defconfig and the bitbake generated .config, they
 >> are quite similar, but the CONFIG_UNION_FS=y line magically shows up.
 >> I'm wondering where it comes from and how to disable it.
 >
 > CONFIG_UNION_FS is being enabled by the standard kernel (and all
 > kernels that inherit it). Since you are based on that kernel, you
 > get the option enabled.
 >
 >>
 >> I can do a bitbake -c menuconfig virtual/kernel and eliminate that
 >> option giving me the kernel I want, but those changes are gone after a
 >> bitbake -c cleansstate ...
 >
 > Have you tried putting
 >
 > # CONFIG_UNION_FS is not set
 >
 > in your defconfig ? That should disable it.
 >
I did try that, but that did not disable it.

So after much pain and thrashing about to figure things out, now I see 
that in the standard-nocfg.scc file, the unionfs feature is set. This 
file is found in the following path: tmp/work/.. 
../linux/meta/cfg/kernel-cache/ktypes/standard/ directory.

My current burning question is:  Where is does this file come from? It 
does not seem to be part of the kernel git repository.  I can changes 
this file and affect the kernel build, but again, those changes are 
transitory and do not persist after cleaning.

Thanks,

Brian