[yocto] using BBMULTICONFIG to create a 32-bit rootfs, kernel, u-boot that also includes a 64-bit kernel, u-boot for NXP i.mx6/i.mx8

[Davis Roman]

Hi Joshua,

Thank you for replying.

Since my last email, I enabled BBMULTICONFIG and was able to build both
32bit and 64bit machine types successfully and so i have both packages
available in their corresponding build folders.

build/tmp-imx6sxsabresd/deploy/rpm/imx6sxsabresd/kernel-4.14.98-r0.imx6sxsabresd.rpm
build/tmp-imx8mmevk/deploy/rpm/imx8mmevk/kernel-4.14.98-r0.imx8mmevk.rpm

I checked out mcdepends however I don't believe this helps me to do the
last piece which is to pull the 64-bit kernel package into my 32-bit image.
According to the yocto docs, mcdepends ensures that imageA is built only
after imageB has finished building (or at least that's how I understand it).

In parallel, I'm studying a patch that was upstreamed in 2017 for adding
support for multiple kernel packages (
http://lists.openembedded.org/pipermail/openembedded-core/2017-October/143674.html
)
This appears to be in line with what I'm looking to do however the wrinkle
is that I'm dealing with two kernels from two different machine types
whereas the patch dealt with two kernels of the same machine type.
I'm still trying to understand the implications of this. My feeling is that
I need a hybrid approach of bbmulticonfig and the above patch for adding
multiple kernel packages.

Please let me know if you have any thoughts.

Thanks,

Davis

On Fri, Oct 4, 2019 at 10:59 PM Joshua Watt <jpewhacker at gmail.com> wrote:

>
>
> On Fri, Oct 4, 2019, 7:04 PM Davis Roman <davis.roman84 at gmail.com> wrote:
>
>> Hello,
>>
>> We're working on a Linux distro for two systems where one is based on
>> NXP i.mx6(32-bit,armv7) and the other i.mx8(64-bit,armv8).
>>
>> I have two machine types defined in Yocto so individually I can build
>> either one however our goal is to create a single distro that can run on
>> both processors.
>>
>> So the idea is to use BBMULTICONFIG(
>> https://www.yoctoproject.org/docs/latest/ref-manual/ref-manual.html#var-BBMULTICONFIG
>> )
>> to build two separate images,
>>
>> 1) a 32-bit distro for an i.mx6
>> 2) a 64-bit distro for an i.mx8
>>
>> and then finally, take the 32-bit distro and add the 64-bit
>> kernel+modules and u-boot.
>>
>> ---------------------------------------
>> |--------------------------------------|
>> ||           32-bit rootfs            ||
>> |--------------------------------------|
>> |-----------------   ----------------- |
>> || 32-bit kernel |   |  64-bit kernel ||
>> |-----------------   ----------------- |
>> |-----------------   ----------------- |
>> || 32-bit u-boot |   |  64-bit u-boot ||
>> |-----------------   ----------------- |
>> ---------------------------------------
>>    i.mx6solo             i.mx8m mini
>>
>> We've already tried our existing 32-bit rootfs + 64-bit kernel/u-boot on
>> the i.mx8 and the system runs.
>> So in theory, it should just be a matter of getting yocto to assemble
>> all the pieces together.
>>
>> I don't have much experience with BBMULTICONFIG so any ideas or comments
>> on how to proceed would be appreciated.
>>
>
> You are on the right track. Create two multiconfig files one for each
> machine, then user mcdepends (
> https://www.yoctoproject.org/docs/current/mega-manual/mega-manual.html#dev-enabling-multiple-configuration-build-dependencies)
> to pull the 64 bit kernel, etc. into the 32 bit image.
>
> BBMULTICONFIG is used in local.conf to select which multiconfigs you want
> to enable. In your case it would have to list both of the ones that you
> define.
>
>
>> Thank you,
>>
>> Davis
>> --
>> _______________________________________________
>> yocto mailing list
>> yocto at yoctoproject.org
>> https://lists.yoctoproject.org/listinfo/yocto
>>
>
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