[yocto] [meta-raspberrypi] how to apply custom kernel configuration?

[Bruce Ashfield]

On 2017-05-08 6:08 PM, Andrei Gherzan wrote:
> On Sat, May 6, 2017 at 6:14 PM, Khem Raj <raj.khem at gmail.com> wrote:
>> On Sat, May 6, 2017 at 9:45 AM, Andrea Galbusera <gizero at gmail.com> wrote:
>>> Hi!
>>>
>>> I was wondering how to apply some extra kernel configuration from a custom
>>> layer via a bbappend. I know that with meta-raspberrypi there exist some
>>> variables you can define in local.conf that will drive how the kernel is
>>> configured: but what about some very specific device driver nobody than me
>>> is interest in? To me it seems it doesn't deserve a dedicated global oe
>>> variable.
>>>
>>> Some investigation showed this topic already came up on the list from time
>>> to time in the past (most recently in [1]). To me it looks like there is
>>> some common desire to get rid of the current "magic" carried out by
>>> linux-rpi.inc by moving the linux-raspberrypi recipes into the configuration
>>> fragments style.
>>>
>>> In the short term, my question are: how do you guys manage to add your
>>> custom kernel configurations? Do you rely on full blown static defconfigs?
>>> Have you found any reliable way to do "differential" configurations with the
>>> current state of metadata?
>>>
>>> In a longer term, I'd really like to help moving towards supporting
>>> configuration fragments for linux-raspberrypi, but I suspect it'd be a too
>>> much hard task for my current understanding of the whole kernel
>>> configuration workflow. Do you know of anyone already working on this or
>>> does anyone have a clear idea of what is needed to get the work done? Some
>>> times ago I tried to resurrect [2], but with no luck, probably due to some
>>> changes that happened in the linux-yocto files in the meanwhile.
>>>
>>> Comments from gurus are welcome! ;-)
>>
>> I have been hinting at using yocto kernel tooling. Idea is worth a pull request
>> care sending one ?
>
> I'm not using config fragments myself but I was under the impression
> that we do support it.

Also FWIW, I've had a feature around for quite a while that I'll
complete in the 2.4 release cycle. That feature pulls the core fragment
processing into the main kernel classes (with auditing, etc, still in
kernel-yocto).

So doing an inherit of kernel-yocto won't be necessary at that point
.. which may ease the introduction of some config fragments.

Bruce

>
> --
> Andrei Gherzan
>