[yocto] Preempt-rt kernel build for beagleboard

[Bruce Ashfield]

On 12-11-28 01:07 AM, Yu Pan wrote:
> Hi Bruce,
>
> Thanks for commenting :-)
>
>     You shouldn't have needed to do this part, since the board already has
>     a preempt-rt BSP description:
>
>     http://git.yoctoproject.org/__cgit/cgit.cgi/linux-yocto-3.4/__tree/meta/cfg/kernel-cache/__bsp/beagleboard/beagleboard-__preempt-rt.scc?h=meta
>     <http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-3.4/tree/meta/cfg/kernel-cache/bsp/beagleboard/beagleboard-preempt-rt.scc?h=meta>
>
>     And when you build the linux-yocto-rt kernel with that board, that
>     description should be found, and it enables all the base options
>     already.
>
>     If you look in your build, what does the file 'linux/meta/top_tgt'
>     contain ?
>
>
> This was what puzzles me as well. I thought bitbake should pickup what

It's the kern-tools that find the .scc file based on information passed
in from bitbake, in this case, the board name and the kernel type.

> is specified in beagleboard-preempt-rt.scc to produce the .config in the
> kernel build directory. But it did not, at least for the PREEMPT part.
> Below is the PREEMPT related configs in the .config without manually
> doing the menuconfig:
>
> # CONFIG_PREEMPT_RCU is not set
> CONFIG_PREEMPT_NONE=y
> # CONFIG_PREEMPT_VOLUNTARY is not set
> # CONFIG_PREEMPT__LL is not set
> # CONFIG_PREEMPT_RTB is not set
> # CONFIG_PREEMPT_RT_FULL is not set
>
> Follow your pointer, I checked linux/meta/top_tgt, it indeed points to
> meta/cfg/kernel-cache/bsp/beagleboard/beagleboard-preempt-rt.scc, which

And this means that the right one was found.

> includes ktypes/preempt-rt (why not ktypes/preempt-rt.scc?). In
> ktypes/preempt-rt.cfg (included by ktypes/preempt-rt.scc),
> CONFIG_PREEMPT_RT_FULL=y is there. So why not this configuration
> fragment not picked up in the final .config?

It should always make it into the final .config, are you working on
master ? I'll run my own tests here to see if I can reproduce the
failure. Master should also have a better Kconfig audit report, are
you seeing any messages about Kconfig options being dropped ?

Cheers,

Bruce

>
> Cheers
> Pan Yu