[yocto] QEMU kernel defconfigs

[Bruce Ashfield]

On 2018-11-15 12:29 p.m., Jon Mason wrote:
> I'm having difficulty determining where the kernel defconfigs are
> defined and located.  I'm specifically looking for the qemuarm and
> qemuarm64 kernel defconfigs.  I've looked at the relevant
> documentation, https://www.yoctoproject.org/docs/2.5.1/kernel-dev/kernel-dev.html#using-an-in-tree-defconfig-file
> and
> no SRC_URI with defconfig or KBUILD_DEFCONFIG_KMACHINE defined in
> meta/recipes-kernel/linux/linux-yocto_4.18.bb
> 
> What am I missing?

The reference machines with linux-yocto don't use defconfigs at all.
They are fully assembled from the configuration fragments in the
kernel-cache repo.

You'll see the location of the kernel-cache, and the routines that
gather up the fragments in the linux-yocto* recipes.

The kernel development manual has that detail as well:

https://www.yoctoproject.org/docs/2.5.1/kernel-dev/kernel-dev.html#kernel-dev-advanced

Bruce

> 
> Also, "A defconfig file is simply a .config renamed to "defconfig"."
> is not correct.  A properly created defconfig is created by `make
> savedefconfig` and is a minimal file which only has the delta between
> the desired config and defaults from the Kconfig files.
> https://www.yoctoproject.org/docs/2.5.1/kernel-dev/kernel-dev.html#creating-a-defconfig-file
> 
> Thanks,
> Jon
>