Re: [yocto] Building and selecting multiple kernel versions

["Quentin Schulz" <quentin.schulz@streamunlimited.com>]

Hi Ryan,

On Mon, Feb 03, 2020 at 05:34:23PM +0000, Ryan Harkin wrote:
> Hello all,
> 
> I'm looking for advice on how to support multiple kernel versions in my
> distro with minimal changes, and minimal disruption to my users.
> 
> Some background:
> 
> I have a legacy Sumo based distro with an image config, and a machine
> config, with the machine using a 4.9 kernel. Last year, I upgraded
> everything to Warrior, and moved to a 4.19 kernel.
> 
> Some of my users who are migrating from Sumo, wish to keep their 4.9
> kernel. So I'm trying to work out how to handle this in the simplest way.
> 
> I know that I can add a 4.9 recipes to my Warrior branches, set
> PREFERRED_VERSION in my distro.conf. But I don't want to change the default
> preferred version globally. And I don't really want users to update the
> distro.conf. Ideally, they should be able to take what I give them and
> "just" build it to get a 4.9 or 4.19 variant.
> 

You can make two machine configuration files. One with
PREFERRED_VERSION_virtual/kernel = "4.9%" and the other with 4.19.

They pick the correct machine when building, they should expect the
correct kernel in output. Only applies to images built for this machine
so I guess that's what you're looking for?

> Ideally, I don't want to *have* to build both kernels and then create two
> images. I expect that will cause confusion and lead to people flashing the
> wrong images. So I'd prefer it to be either/or. Of course, I have to test
> all of this, so I want to be able to build both variants in CI, which makes
> editing distro.conf even more  unattractive.
> 

Same image (POV of bitbake <image>) but different machines, does that
match your requirements?

FWIW, you can pass MACHINE= to the command line just before bitbake
<image> making it rather obvious which machine they pick.

Quentin