[meta-xilinx] US+ MPSoC Default Kernel Config vs Kernel Meta Data

[Nathan Rossi]

On 17 October 2017 at 02:44, Peter Smith <salerio at gmail.com> wrote:
> A question for someone with more knowledge than me. How do the Xilinx
> default config for zynqmp i.e. KBUILD_DEFCONFIG-zynqmp =
> “xilinx_zynqmp_defconfig” and the kernel meta data contained in the
> recipes-kernel/linux/config directory interact? Is one added after the
> other, does one override the other, you get the idea. Thanks Peter

Using KBUILD_DEFCONFIG with kernels that include/inherit linux-yocto
(such as linux-xlnx) is the same behavior as linux-yocto supports by
providing a 'defconfig' file via SRC_URI. This essentially treats the
defconfig as the first config fragment, the kmeta (the metadata in
linux/config/xilinx-*) is applied after and can override what is set
in the defconfig.

Currently with linux-xlnx, KMACHINE is also setup which causes the
inclusion of zynqmp-standard.scc. This layers on top the defconfig
with config fragments that are used for zynq/microblaze targets, which
are equivalent to the xilinx*defconfig but re-implemented as
fragments. This does mean that for zynqmp there is duplication of
config between the defconfig and the fragments, but there is no
removal of config in the fragments of meta-xilinx.

For linux-xlnx this is to change slightly with the planned merge of
this series (https://lists.yoctoproject.org/pipermail/meta-xilinx/2017-October/003183.html).
Which makes linux-xlnx configured only by KBUILD_DEFCONFIG and any
features that are setup in KERNEL_FEATURES/SRC_URI, and does not use
or set any KMACHINE.

Regards,
Nathan