Re: [PATCH 5/5] kernel: use architecture specific names for kernels

["'MOESSBAUER, Felix' via isar-users" <isar-users@googlegroups.com>]

On Thu, 2026-08-13 at 19:47 +0200, Jan Kiszka wrote:
> On 13.08.26 18:45, Felix Moessbauer wrote:
> > The kernel source packages are architecture specific. By that, we also
> > have to encode the architecture in the KERNEL_NAME, if that is not
> > already implicitly the case (e.g. when building a kernel for a specific
> > machine).
> > 
> > For the kernel recipes which are generic (like mainline and cip), we
> > simply extend the PN with -${DISTRO_ARCH}, so bitbake can find the
> > dependency and instanciate an architecture specific variant.
> > 
> > By that, we also need to adapt the default in test_per_kernel, which
> > explicitly builds the module for the kernel that corresponds to the
> > multiconfig target.
> > 
> > Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
> > ---
> >  RECIPE-API-CHANGELOG.md                        | 18 ++++++++++++++++++
> >  meta-isar/conf/machine/beagleplay.conf         |  2 +-
> >  meta-isar/conf/machine/de0-nano-soc.conf       |  2 +-
> >  meta-isar/conf/machine/hikey.conf              |  2 +-
> >  meta-isar/conf/machine/qemuamd64-cip.conf      |  2 +-
> >  meta-isar/conf/machine/sifive-fu540.conf       |  2 +-
> >  meta-isar/conf/machine/stm32mp15x.conf         |  2 +-
> >  .../linux/linux-cip_4.4.166-cip29.bb           |  2 ++
> >  .../linux/linux-mainline_6.12.85.bb            |  2 ++
> >  testsuite/citest.py                            |  2 +-
> >  10 files changed, 29 insertions(+), 7 deletions(-)
> > 
> > diff --git a/RECIPE-API-CHANGELOG.md b/RECIPE-API-CHANGELOG.md
> > index 2db05169..c13a3b3f 100644
> > --- a/RECIPE-API-CHANGELOG.md
> > +++ b/RECIPE-API-CHANGELOG.md
> > @@ -1175,6 +1175,24 @@ DPKG_ARCH ?= "${DISTRO_ARCH}"
> >  
> >  Firmware packages are an exception because they are built for only one architecture.
> >  
> > +### Kernel source packages are architecture specific
> > +
> > +Kernel source packages have always contained architecture-specific content, but
> 
> See my comment on the cover letter: architecture or even
> machine-specific content.

This does not invalidate this statement. It just means there could be
even more differences. Anyways, just a cover letter ;)

> 
> > +this was not previously enforced. As a result, builds for multiple architectures
> > +could publish different source packages with the same name and version.
> > +
> > +Generic kernel recipes can append `${DISTRO_ARCH}` to `PN`, to provide the
> > +kernel for all architectures.
> > +
> > +```
> > +PN .= "-${DISTRO_ARCH}"
> > +```
> > +
> > +For a kernel built for only one target, the name may remain unchanged. When
> > +building multiple instances of a kernel selected by the same `KERNEL_NAME`, use
> > +`${DISTRO_ARCH}` in the name for architecture-specific kernels, or `${MACHINE}`
> > +for machine-specific kernels.
> > +
> 
> This is not written like a recipe API change. This way, it looks like
> something that belongs into the user manual, kernel section, as it
> provides guidance on how to model that special case. You need to
> explain, when this is now required while it was not before.
> 
> But I would rather suggest modelling that more transparently, via
> PROVIDES: The KERNEL_NAME should remain "mainline", e.g., and the
> recipes should PROVIDE that generic name while actually building
> "mainline-$DISTRO_ARCH".

And this is exactly what "option 2" from [1] proposes, which I tried
and which does not work for two reasons:

1. on bitbake side, the provides and depends need to be fiddled through
the multiarch classes (-native), which I did not manage to implement.
For the kernel it worked, but not for the module recipes. It also gets
super messy on multiconfig builds with two different kernels (e.g. a
hardened one for the image and a "open" one for the installer).

2. We need provides on the debian package names as well, but resolving
multiple provides in the dependency install stages (sbuild and rootfs
install) is tricky, as we already know from other tries in this
direction.

Felix

> Jan
> 
> -- 
> Siemens AG, Foundational Technologies
> Linux Expert Center

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