Re: [GNU-linux-libre] Replacing Yocto with Guix kernel image builds: best practices

[Begley Brothers Inc <begleybrothers@gmail.com>]

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On Sun, May 17, 2020 at 10:55 PM Ricardo Wurmus <rekado@elephly.net> wrote:

>
> Hi,
>
> [+guix-devel, -gnu-linux-libre]
>
> > We are now looking to build Linux kernels using Guix instead of Yocto.
> We
> > can't see any reason why the builds wouldn't be linux-libre. Ideally we'd
> > like our effort to be accepted by upstream guix.
> […]
> > We'd appreciate any pointers to package definition(s) that demonstrate
> best
> > practices to do what we'd like:
> >
> > - We'd like to build custom configured kernels for each patch series in
> the
> > LTS 4.14.72+, 4.19+ and 5.4+.
> > - Currently we have two `base` kernel configs that each 'variant'
> > configuration is applied to for each of a machine 'type' (3 machine
> types)
> > and one of two 'arch'.
> > - Currently we can generate a full kernel `.config` for a
> > kernel+base+variant+arch (we are working on the best way to handle
> > different machines if we are not using Yocto.)
> > - We'd ideally like to generate `vmlinux`, `initrd` and `rootfs` images
> for
> > each.
> >
> > Based on Efraim's post we think the first example is the least friction -
> > "including an actual .config file as a native input to our custom
> kernel".
> > Assume we resolve the machine definition issue.  However we're puzzled
> > about how to best distribute the configuration file such that a build of
> > kernel x.y.z can be updated with fixes.
>
> You can either put your config files in a separate git repository and add
> that to
> the native inputs, or you can include the config files in your channel
> repository (or later in Guix itself).
>

Thanks for the suggestion.  That gives some assurance.
Could you point to an existing guix (upstream) package that is a best
practice
example of each of those two approaches?
- accessing files from a separate repo
- a guix (upstream) package using other files

> The constraint of users being able to use the std guix commands rather
> than
> > telling them to download a config file or clone a git repo and copy a
> > config file is what is puzzling. Some options we thought about seem
> > inelegant - hence too embarassing to mention - so we'll skip them ;)
> > Leaving....
> >
> > 1) We did wonder if channels[2] were the way to go with each kernel x.y.z
> > in its own branch and config files therein. Could anyone point us to
> > packages that setup and use package specific channels?
>
> Channels handle all the gnarly bits of interacting with git.  Users who
> would like to add your channel providing alternative kernels would only
> need to add it to their ~/.config/guix/channels.scm file.
>

Can "add it to their ~/.config/guix/channels.scm file" be scripted as part
of the
package?
Is there an example of a guix (upstream) package that does this?

But since your stated goal is to add these definitions to Guix itself
> you can simply add the kernel variants to linux.scm and include the
> config files in the repository.
>

Current guix/linux.scm seems to take a different approach and cater to a
different use cases - but our understanding of the code is limited and no
doubt flawed.
We think a three step process:

1. Get a package definition working and publicly available.
2. Make any changes to get it accepted as a separate package by guix.
3. Consider whether merging with guix/linux.scm is what linux-libre folks
    want

> 2) Should we be aiming to provide a single package with multiple
> parameters
> > or is it better to provide a package for each kernel x.y.z, or some other
> > partitioning. We'd likely want to script the package definition then -
> > correct?
>
> If the main differences between kernel variants are not in the package
> definition but the sources and the configuration file I’d suggest
> defining a procedure that returns a package value.  You can then define
> multiple packages in terms of that procedure.
>

Thanks for that suggestion.  It seems the issue to resolve is the best
approach for getting those config files to the users machine.

Thanks again


> --
> Ricardo
>


-- 
Kind Regards

Begley Brothers Inc.


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