[yocto] Building Out-of-Tree Modules on the BBB Target

Zoran Stojsavljevic zoran.stojsavljevic at gmail.com
Wed May 15 00:44:14 PDT 2019 

> That's correct. That command only adds the kernel source and
> build infrastructure to the SDK, not to your target image. *You'd still*
*> need to arrange to have the kernel-devsrc package installed on the*
*> target image if you want it on the board's rootfs.* How you arrange
> to have the package installed to the image varies with the image
> (since they all don't have the same image install variables, etc).

And here is a $1,000,000 USD question? How to do it on Poky (as
example of what you have stated in RED)? ;-)

In other words: how to arrange it on Poky (as a Referent example)?

Thank you,
Zoran
_______


On Wed, May 15, 2019 at 7:41 AM Bruce Ashfield <bruce.ashfield at gmail.com>
wrote:

>
>
> On Tue, May 14, 2019 at 1:30 PM Zoran Stojsavljevic <
> zoran.stojsavljevic at gmail.com> wrote:
>
>> Hello Chris, Bruce,
>>
>> I have some additional data to share with you both, since I have tried
>> something. And here is my take on the things!
>>
>> > 1. Build using a bb recipe.
>> > Take a look at meta-skeleton/recipes-kernel/hello-mod for an example.
>> > You just need to add meta-skeleton to your bblayers.conf and then
>> >  bitbake hello-mod
>>
>> I looked into this example, and, yes, it is classic kernel module
>> definition out of the tree. With some outdated data, all cool, the
>> YOCTO designer should take care himself to fix these data, if using
>> this stuff.
>>
>> But this is NOT mandatory, since I can add out of the tree module NOT
>> actually using built-in module. I just use .../tmp/deploy/images/bbb/*
>> generated stuff, since I have automated scripts which are bringing all
>> these on my BBB target. Then I tftp my source code module to the
>> target.
>>
>> > 2. Build from the SDK:
>> > First, add the kernel source to the SDK by adding this to
>> conf/local.conf
>> >  TOOLCHAIN_TARGET_TASK_append = " kernel-devsrc"
>>
>> YES, this is THE command which should generate
>> /usr/src/kernel(s)/`uname -r` or similar... But adding it to
>> local.conf and after deleting kernel, then regenerating bitbake -k
>> core-image-minimal does not bring this path into the rootfs image!?
>>
>
> That's correct. That command only adds the kernel source and build
> infrastructure to the SDK, not to your target image. You'd still need to
> arrange to have the kernel-devsrc package installed on the target image if
> you want it on the board's rootfs. How you arrange to have the package
> installed to the image varies with the image (since they all don't have the
> same image install variables, etc).
>
>
>
>>
>> I did it actually using meta-bbb, and using poky referent distro as
>> two additional layers to the more complex bbb image!
>> https://github.com/jumpnow/meta-bbb.git
>>
>> The (KAS - you can figure out out of it local.conf) script I am using
>> to build such a BBB image is here:
>>
>> https://github.com/ZoranStojsavljevic/bbb-yocto/blob/master/bbb-releases/bbb-warrior/kas-bbb-warrior.yml
>>
>> I did not try it with BBB reference poky only! Maybe I should try it
>> as only referent poky? What do you think?
>>
>> Does in this case is SDK build really mandatory??? Should NOT be!
>>
>>
> You only do the SDK steps if you want to support building out of tree
> modules in an SDK install. So it is not mandatory for on target module
> builds.
>
> Bruce
>
>
>
>> > Once the SDK is installed, generate the kernel headers:
>> >  sudo -i
>> >  . /opt/poky/2.6.2/environment-setup-cortexa8hf-neon-poky-linux-gnueabi
>> >  cd /opt/poky/2.6.2/sysroots/cortexa8hf-neon-poky-linux-gnueabi
>> >  cd /usr/src/kernel
>> >  make oldconfig scripts
>> >  exit
>>
>> This is in nutshell the same what I did (a bit different) for Embedded
>> Debian. This is already on the target BBB, NOT while building YOCTO
>> BBB image!
>>
>> > Finally, build your module using a Makefile like this
>> >  obj-m := hello-mod.o
>> >  all:
>> >        make -C $(SDKTARGETSYSROOT)/usr/src/kernel M=$(shell pwd)
>>
>> As said before: bringing my own module into the target BBB (I have my
>> own examples, and I build them on the target with the almost the same
>> Makefiles)
>>
>> Zoran
>> _______
>>
>> On Sun, May 12, 2019 at 3:15 PM Chris Simmonds <chris at 2net.co.uk> wrote:
>> >
>> > Hi Zoran,
>> >
>> > There are two ways to do this
>> >
>> > 1. Build using a bb recipe.
>> > Take a look at meta-skeleton/recipes-kernel/hello-mod for an example.
>> > You just need to add meta-skeleton to your bblaysers.conf and then
>> >   bitbake hello-mod
>> >
>> >
>> > 2. Build from the SDK:
>> > First, add the kernel source to the SDK by adding this to
>> conf/local/conf
>> >   TOOLCHAIN_TARGET_TASK_append = " kernel-devsrc"
>> >
>> > Then build the SDK
>> >   bitbake -c populate_sdk [your image recipe]
>> >
>> > Once the SDK is installed, generate the kernel headers:
>> >   sudo -i
>> >   . /opt/poky/2.6.2/environment-setup-cortexa8hf-neon-poky-linux-gnueabi
>> >   cd /opt/poky/2.6.2/sysroots/cortexa8hf-neon-poky-linux-gnueabi
>> >   cd /usr/src/kernel
>> >   make oldconfig scripts
>> >   exit
>> >
>> > Finally, build your module using a Makefile like this
>> >
>> >   obj-m := hello-mod.o
>> >   all:
>> >         make -C $(SDKTARGETSYSROOT)/usr/src/kernel M=$(shell pwd)
>> >
>> >
>> > HTH,
>> > Chris
>> >
>> > On 12/05/2019 11:53, Zoran Stojsavljevic wrote:
>> > > Hello to the YOCTO community,
>> > >
>> > > I am using (to build the target for Beagle Bone Black) the following
>> script:
>> > > https://github.com/ZoranStojsavljevic/bbb-yocto
>> > >
>> https://github.com/ZoranStojsavljevic/bbb-yocto/blob/master/bbb-yocto.sh
>> > >
>> > > The latest kernel I am using from the following repo:
>> > > https://github.com/jumpnow/meta-bbb
>> > >
>> > > Is kernel 5.0.14 .
>> > >
>> > > Here is the snippet of the boot traces:
>> > > Starting kernel ...
>> > >
>> > > [    0.000000] Booting Linux on physical CPU 0x0
>> > > [    0.000000] Linux version 5.0.14-jumpnow (oe-user at oe-host) (gcc
>> > > version 8.3.0 (GCC)) #1 Fri May 10 13:12:33 UTC 2019
>> > > [    0.000000] CPU: ARMv7 Processor [413fc082] revision 2 (ARMv7),
>> cr=10c5387d
>> > > [    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing
>> > > instruction cache
>> > > [    0.000000] OF: fdt: Machine model: TI AM335x BeagleBone Black
>> > > [    0.000000] Memory policy: Data cache writeback
>> > > [    0.000000] cma: Reserved 16 MiB at 0x9f000000
>> > > [    0.000000] CPU: All CPU(s) started in SVC mode.
>> > > [    0.000000] AM335X ES2.1 (sgx neon)
>> > > [    0.000000] random: get_random_bytes called from
>> > > start_kernel+0xa4/0x460 with crng_init=0
>> > > [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages:
>> 130048
>> > > [    0.000000] Kernel command line: console=ttyO0,115200n8
>> > > root=/dev/ram0 ip=dhcp
>> > >
>> > > According to the documentation, the following:
>> > > 2.10.1. Building Out-of-Tree Modules on the Target
>> > > https://www.yoctoproject.org/docs/latest/kernel-dev/kernel-dev.html
>> > >
>> > > I tried to find /usr/src/kernels/5.0.14... Directory, since I see
>> > > from the build that kernel-dev and kernel-devsrc are included:
>> > > [user at fedora29-ssd bbb-yocto]$ bitbake -s | grep kernel
>> > > core-image-kernel-dev                                 :1.0-r0
>> > > kernel-devsrc                                         :1.0-r0
>> > > kernel-selftest                                       :1.0-r0
>> > >
>> > > THE PROBLEM: But I could not find ob BBB target /usr/src/kernels
>> > > directory at all!?
>> > >
>> > > Two questions here?
>> > > [1] Do you have any advice on this problem (what I am missing here)?
>> > > [2] Alternative to [1]: how I can use cross compiler from
>> > > .../build/tmp to build Out-of-Tree Module for the BBB target on the
>> > > host?
>> > >
>> > > Thank you,
>> > > Zoran
>> > > _______
>> > >
>> >
>> >
>> > --
>> > Chris Simmonds, trainer and consultant at 2net
>> > http://www.2net.co.uk
>> > Author of "Mastering Embedded Linux Programming"
>>
>
>
> --
> - Thou shalt not follow the NULL pointer, for chaos and madness await thee
> at its end
> - "Use the force Harry" - Gandalf, Star Trek II
>
>
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