[yocto] Variable locality too restricted.

[Bruce Ashfield]

On Thu, Dec 8, 2011 at 2:24 AM, David Nyström <David.Nystrom at enea.com> wrote:
>
> ________________________________________
> From: Koen Kooi [koen at dominion.thruhere.net]
> Sent: Wednesday, December 07, 2011 15:07
> To: Paul Eggleton
> Cc: Chris Larson; David Nyström; yocto at yoctoproject.org
> Subject: Re: [yocto] Variable locality too restricted.
>
> Op 7 dec. 2011, om 15:05 heeft Paul Eggleton het volgende geschreven:
>
>> On Wednesday 07 December 2011 06:52:25 Chris Larson wrote:
>>> On Wed, Dec 7, 2011 at 6:44 AM, David Nyström <David.Nystrom at enea.com>
>> wrote:
>>>> I'm trying to create a setup for qemuppc.
>>>>
>>>> Goals:
>>>> core-image-minimal + virtual/kernel.
>>>> core-image-minimal + virtual/kernel with modified .config for debug
>>>> flavoured kernel.
>>>>
>>>> Problems:
>>>> PREFERRED_PROVIDER seems to be restricted to local.conf, distro and
>>>> machine.
>>> This is incorrect. It can be anywhere in the configuration metadata.
>>> bitbake.conf includes a variety of config files, not just
>>> distro/machine. Read that to see other existing files which get
>>> included. Further, you could create a .conf/.inc which you include
>>> from your machine .conf, if your goal is just to avoid duplication.
>>
>> Changing MACHINE has other implications though; do we not have any other way
>> to switch out the kernel on a per-image basis?
>
> And how would that work from a packaging perspective? AIUI changing DISTRO/MACHINE flags in an image is a recipe for failure.
>
> regards,
>
> Koen
> Op 7 dec. 2011, om 15:10 heeft Paul Eggleton het volgende geschreven:
>
> --
>> On Wednesday 07 December 2011 15:07:54 Koen Kooi wrote:
>>>> Changing MACHINE has other implications though; do we not have any other
>>>> way to switch out the kernel on a per-image basis?
>>>
>>> And how would that work from a packaging perspective? AIUI changing
>>> DISTRO/MACHINE flags in an image is a recipe for failure.
>>
>> I'm not suggesting changing the kernel configuration for the existing kernel;
>> naturally you would need a different kernel recipe. Surely you should just be
>> able to have a different kernel that is built and installed for a different
>> image file? No invalidated packages necessary.
>
> A kernel buld will generate packages and thanks to kernel.bbclass they will have similar names. So what will happen when I do:
>
> bitbake foo-image bar-image
>
> ? Will it build 2 kernels? Which kernel will end up being packaged or will there be a mix of both in deploy?
>
> regards,
>
> Koen
>
> --
>
> Different virtual/kernel recipies depending on kernel configuration might not be the best resolution path for this issue.
>
> How would it be problematic to have multiple binary flavour packages(Still a single source package)
> of the same kernel with the same linux-headers in the distro packages ?
> In deploy/images a similiar notation as for rootfs could be used.
> Perhaps there are no mechanisms today to do this, but perhaps there could/should be ?
> What about a pkgconfig style approach ?
>
> poky configuration contains a logical separation of IMAGE, MACHINE and DISTRO. (Probably more, but this is unrelated to my point below).
> What is the roadmap and future of this separation ?
>
> image:
> The IMAGE may contain user applications that will not function without the proper kernel modules.(Or possibly non-module available .config items).
> i.e. RDEPENDS = kernel-module-xxxx will is impossible to automate since it only scans kernel build for its existence.(if it was configured by kernel .config monolith selected by MACHINE)
> This is solved in most recipies as RRECOMMENDS = kernel-module-xxx to avoid build breakage.
>
> So you need to configure your kernel to support all your IMAGEs, from core-image-smaller-than-minimal to core-image-huge-system(or in my case debug, profiling)
> This is especially problematic for small embedded systems when it comes to debug and profiling, where included kernel configuration(depending on exactly what)
> will have varying degrees of performance impact.(some huge, others we can probably live with).
>
> machine:
> In my head, this would contain machine specific configuration and not deal with other kernel configuration.
> In edison, the kernel configuration is treated as a monolith, perhaps we can improve this by allowing for a more dynamic configuration model of the kernel, where the
> machine logical layer would depend on _only_ the machine specific parts of the kernel configuration. In the current(edison) case, it usually uses a defconfig.
> Great, but let the build modify it.
>
> pipedream:
> 1. MACHINE selects a defconfig.
> 2. IMAGE selects packets on rootfs, some depend on kernel-module-xx, or kernel-config-xx.
> 3. When building image, fist stage scans included recipes for kernel-module-* and kernel-config-* and adds this to the MACHINE selected defconfig before building kernel.

Hi David,

For what it's worth, if you use the linux-yocto tooling/base kernel,
there are alternate
and modular ways to do something that sounds like what you are
describing with the
kernel configuration. I won't claim to have all the answers with how
this impacts
packaging, image creation, etc. I'm simply talking as a "kernel guy",
and my understanding
of what you are trying to do.

In this scenario, the base BSP inherits the standard/policy kernel configuration
fragments that are part of the kernel tree. It then adds board
specific (hardware) options
and overrides of optional functionality (where optional is defined by
the base configuration).

If you want to then modify the configuration slightly using either
in-tree or add on kernel
configuration fragments you can simply add a .cfg to the SCR_URI or set the
KERNEL_FEATURES variable, just like Darren did recently.

   KERNEL_FEATURES_append_fri2 += " cfg/smp.scc cfg/efi-ext.scc"

Cheers,

Bruce
> Possibly, all kernel related stuff can be located to kernel-profiling-flavour.bb, where recipes are depending on a flavour instead of directly to the kernel-config-xxx.
> 4. Continues with otherwise normal build-flow.
> 5. deploy/ipk..rpm..deb: Kernel binary packages are given a flavour.(Still the same kernel source package).
> 6. deploy/images: keeping a scheme of images similiar to rootfs:es.
>
> Impossible ?
>
> Best Regards,
> David
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