Using kernel fragments with Yocto

[JasonT]

Hi,

We are developing a custom Yocto metalayer that is based on the sama5d27-som1-ek using the linux-at91_4.19.bb kernel recipe.

In our own layer we are using patch files for source code modifications and kernel fragment files for config modifications.
After checking out the source code for linux-at91 using devtool and running bitbake linux-at91 -c menuconfig the patches are successfully applied to the kernel source, but the config fragment file is not applied to the .config for the kernel.

The kernel recipe directory in our custom meta layer is as follows:

recipes-kernel
-----└── linux
-------├── linux-at91
-------|-----├── 0001-example-patch-1.patch
-------│-----├── 0001-example-patch-2.patch
-------│-----└── atmel_fragment.cfg
-------└── linux-at91_%.bbappend

With the content of linux-at91_%.bbappend being:

FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"

SRC_URI_append = "file://atmel_fragment.cfg"

SRC_URI += "file://0001-example-patch-1.patch \
file://0001-example-patch-1.patch \
"

COMPATIBLE_MACHINE = "(custom-machine)"

Does the the linux-at91_4.19.bb recipe support the use of .cfg files to append the defconfig? If so is anyone able to point out where we are going wrong in our custom layer please.