On Tue, 4 Feb 2020 at 16:15, Quentin Schulz <
[email protected]> wrote:

> Hi Ryan,
>
> On Tue, Feb 04, 2020 at 04:00:01PM +0000, Ryan Harkin wrote:
> > Hi Quentin,
> >
> > Thanks for your reply.
> >
> > On Tue, 4 Feb 2020 at 08:51, Quentin Schulz <
> > [email protected]> wrote:
> >
> > > 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?
> > >
> >
> > Yes, this works.
> >
> > Trying it showed a few small problems. Eg. I have a package that only
> builds
> > for the 4.19 kernel, and needs to be excluded for 4.9. That's something I
> > can
> > handle in the recipes using the machine type, of course.
> >
>
> It depends on what exactly does this recipe represent? A kernel module?
> In which case, you can put it in your machine configuration file under
> MACHINE_ESSENTIAL_EXTRA_RDEPENDS or RRECOMMENDS and omit it for 4.9.
>
> We have a way to specify runtime dependencies on specific versions:
>
> https://www.yoctoproject.org/docs/current/mega-manual/mega-manual.html#var-RDEPENDS
>
> I unfortunately have no idea if Yocto supports such a thing in DEPENDS.
>
>
Good tips, thanks again! I'll have a play with it.


> >
> > >
> > > > 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.
> > >
> >
> > Incidentally, that didn't work for me, but that's a symptom of how we
> setup
> > the environment, where local.conf sets MACHINE. I changed it to "MACHINE
> ?=
> > ",
> > thinking it would let me override it via the shell. But it didn't.
> Strange,
> > but not a
> > big problem.
> >
>
> To check who's setting it, run `bitbake <somesimplerecipe> -e | less` and
> look
> for the line starting with MACHINE=. Then you have the whole bitbake
> logic to set it above that line. That could help you find out what's
> happening.
>

Actually, it does work like this:

export MACHINE=xyz
bitbake image

But not like this:

MACHINE=xyz bitbake image

No big deal, but I expected the last one to work.


> Quentin
>
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