On Tue,  6 Jul 2021 13:58:21 -0400
"Bruce Ashfield" [off-list ref] wrote:

From: Bruce Ashfield <redacted>

We are always getting questions about building -stable, or mainline
master. Rather than introducing a separate set of recipes, we can
facilitate this sort of testing by using the existing devupstream
bbclass support.

To build an unpatched or otherwise modifed -stable of 5.13, simply
set the linux-yocto preferred version to:

  upstream+5.13%

And your wish will be granted, as the build will use v5.13/base
which matches the main linux-yocto version, simply with no extra
changes applied.

Signed-off-by: Bruce Ashfield <redacted>

This looks like a good thing to have in oe-core, in the basic case of
just wanting the latest mainline as-is you'd not need to add extra
layers any longer. meta-linux-mainline would still fill a niche as it
provides recipes for older stable kernels and supports using mainline &
newer stable kernels on dunfell & hardknott.

I guess the meta repository (yocto-kernel-cache) would still be cloned
and the upstream kernel could still be modified by patches or config
fragments enabled by KERNEL_FEATURES. That may be worth noting in the
documentation if I'm right. For my use-case where I want to use the
exact upstream defconfig I would probably need to override this, e.g.
`KERNEL_FEATURES_forcevariable = ""`, to make use of this.

I also guess this would also allow you to follow newer kernel releases
as they're added to linux-yocto recipes by setting the preferred version
to 'upstream%' (or maybe 'upstream+%' to be more restrictive). That
would then avoid the build breaking when the 5.13 recipe disappears and
is replaced by 5.14 or something else later.

Thanks,

-- 
Paul Barker
https://pbarker.dev/