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

Bruce Ashfield bruce.ashfield at gmail.com
Wed May 15 15:04:19 PDT 2019


On Wed, May 15, 2019 at 4:09 PM Zoran Stojsavljevic <
zoran.stojsavljevic at gmail.com> wrote:

> > The core-image-kernel-dev image is how I do all my on target
> > testing when I introduce a new reference kernel for a release.
>
> Maybe you are correct. Maybe I should use/add in my local.conf the
> following:
>
> KERNEL_DEV_TOOLS ?= "packagegroup-core-tools-profile
> packagegroup-core-buildessential kernel-devsrc"
> KERNEL_DEV_MODULE ?= "kernel-modules"
> CORE_IMAGE_EXTRA_INSTALL += "${KERNEL_DEV_MODULE} \
>                              ${KERNEL_DEV_TOOLS} \
>                              systemtap \
>                             "
> I need to try these... Maybe this addendum will solve the $1 mio USD
> problem?!
>
> > And IIRC the autobuilders are using a sato based image (Richard
> > could confirm more easily that I could what image type the
> > autobuilders are using for hello-world on target module tests).
>
> I am just advertising something more simple. To have mandatory
> /lib/modules/`uname -r` directory. And introduce few more packages, as
> Fedora distro, for example, has: kernel-headers (assuming YOCTO
> rootfs, the following will be installed: /usr/src/kernel/`uname
> -r`/<header file directory structures>. This also makes addition of
> /lib/modules/`uname -r`/build file (which is soft link to
> usr/src/kernel/`uname -r`).


These have all been discussed off an on over the past 5 years. I can't get
at bugzilla right now, but all the details are logged in cases. A survey of
all the distros, their kernel package, etc, were all looked at. We had to
balance the traditional packaging with some new concepts and landed with
what we have now.



> Or kernel-devel package. Then, the whole current kernel source code
> will be introduced, and also support for it.
>

There's a case for this one as well, I'll probably have it done for the
fall release. But our devsrc used to pretty much be the full source it has
now been pruned down to something more manageable.  There are definitely
some cases for having the full source on the target again, and it will be a
separate package, just not the minimal one to build out of tree modules,
etc.




>
> SDK building with such a support is good/cool. But sometimes, before
> introducing SDK, some tests should be done on target. NO need to
> optionally include built-in layer hello-world driver example. Since I
> (or you name the person) have own test drivers, which will be imported
> out of tree, externally, to the target test bed!
>
>
I never use the SDK myself, so you are not alone in not going to it first.
Hopefully I'll get some new patches out in the coming month before summer
holidays really kick in.

Bruce



> Just thinking loud...
>
> Zoran
> _______
>
> On Wed, May 15, 2019 at 4:25 PM Bruce Ashfield <bruce.ashfield at gmail.com>
> wrote:
> >
> >
> >
> > On Wed, May 15, 2019 at 3:44 AM Zoran Stojsavljevic <
> zoran.stojsavljevic at gmail.com> wrote:
> >>
> >> > 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)?
> >
> >
> > The core-image-kernel-dev image is how I do all my on target testing
> when I introduce a new reference kernel for a release. And IIRC the
> autobuilders are using a sato based image (Richard could confirm more
> easily that I could what image type the autobuilders are using for
> hello-world on target module tests).
> >
> > Bruce
> >
> >
> >>
> >>
> >> 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
> >>>
> >
> >
> > --
> > - Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at its end
> > - "Use the force Harry" - Gandalf, Star Trek II
> >
>


-- 
- 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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