Building and selecting multiple kernel versions

Building and selecting multiple kernel versions

[Ryan Harkin]

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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.

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.

I've considered giving them a "setup-environment" script that edits the
distro.conf for them, but that seems a bit hacky too. And doesn't really
satisfy my CI requirements.

Has anyone done this before? Or do you have some advice about how I could
handle this?

Many thanks,
Ryan.

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Re: [yocto] Building and selecting multiple kernel versions

[Quentin Schulz]

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

Re: [yocto] Building and selecting multiple kernel versions

[Ryan Harkin]

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Hi Quentin,

Thanks for your reply.

On Tue, 4 Feb 2020 at 08:51, Quentin Schulz <
quentin.schulz@streamunlimited.com> 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.


>
> > 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.

I'd be interested to hear if anyone else has a different approach I could
try for
comparison.

Thanks,
Ryan.

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Re: [yocto] Building and selecting multiple kernel versions

[Quentin Schulz]

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 <
> quentin.schulz@streamunlimited.com> 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.

> 
> >
> > > 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.

Quentin

Re: [yocto] Building and selecting multiple kernel versions

[Ryan Harkin]

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On Tue, 4 Feb 2020 at 16:15, Quentin Schulz <
quentin.schulz@streamunlimited.com> 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 <
> > quentin.schulz@streamunlimited.com> 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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Re: [yocto] Building and selecting multiple kernel versions

[Quentin Schulz]

On Tue, Feb 04, 2020 at 04:32:34PM +0000, Ryan Harkin wrote:
[...]
> 
> 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.
> 

I use it every day. I don't think we're doing something special (well,
for that particular thing :D), so there's at least a way to make it work
for sure :)

Quentin

Re: [yocto] Building and selecting multiple kernel versions

[Ryan Harkin]

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On Wed, 5 Feb 2020 at 10:02, Mike Looijmans <
mike.looijmans@topicproducts.com> wrote:

>
> Met vriendelijke groet / kind regards,
>
> Mike Looijmans
> System Expert
>
>
> TOPIC Embedded Products B.V.
> Materiaalweg 4, 5681 RJ Best
> The Netherlands
>
> T: +31 (0) 499 33 69 69
> E: mike.looijmans@topicproducts.com
> W: www.topicproducts.com
>
> Please consider the environment before printing this e-mail
> On 04-02-2020 17:39, Quentin Schulz via Lists.Yoctoproject.Org wrote:
> > On Tue, Feb 04, 2020 at 04:32:34PM +0000, Ryan Harkin wrote:
> > [...]
> >>
> >> 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.
> >>
> >
> > I use it every day. I don't think we're doing something special (well,
> > for that particular thing :D), so there's at least a way to make it work
> > for sure :)
>
> Same here, both interactive and in scripts.
>
> Since the first works, you already have done this:
> export BB_ENV_EXTRAWHITE=MACHINE
>
> Maybe there's something funky in your shell?
> You could check with a command like:
> MACHINE=x env | grep MACHINE
>

 It looks "normal":

$ MACHINE=x env | grep MACHINE
MACHINE=x


> Of maybe somebody wrote a bitbake wrapper for you that forks python
> instead of
> exec'ing it?
>

No, it's the regular bitbake.

I'm not too concerned about this problem anyway, I'm sure if it's a problem
for me, I can work out who is overriding it.

Thanks,
Ryan

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