[yocto] Bitbake Build Configurations

[Andre McCurdy]

On Wed, Oct 17, 2018 at 5:12 AM, Dhanush K.S <dhanush.ks at gmail.com> wrote:
> Hi Yocto,
>
> I have my bitbake environment set up on the host system CentOS 7 and
> building images for the target ARM cortex A8 with the following BUILD
> CONFIGURATION,
>
> Build Configuration:
> BB_VERSION           = "1.37.0"
> BUILD_SYS            = "x86_64-linux"
> NATIVELSBSTRING      = "universal-4.8"
> TARGET_SYS           = "arm-poky-linux-gnueabi"
> MACHINE              = "arm-cortex-a8"
> DISTRO               = "poky"
> DISTRO_VERSION       = "2.5"
> TUNE_FEATURES        = "arm armv7a vfp neon callconvention-hard cortexa8"
> TARGET_FPU           = "hard"
> meta-networking
> meta-python          = "master:45ee3c0e98bd3ed81419aaeae1e7324e486161a2"
> meta-userbsp-ti
> meta
> meta-poky
> meta-yocto-bsp
> meta-user-common      = "<unknown>:<unknown>"
> meta-oe              = "master:45ee3c0e98bd3ed81419aaeae1e7324e486161a2"
>
> What I don't understand is how exactly are these Variables set?
> For the NATIVELSBSTRING which should actually be displaying the HOST OS
> according to the Yocto Manual, isn't doing that. What could be the reason
> for that? (Earlier, with Poky Fido, this wasn't the case. It displays
> "CentOS-Linux-7.1.1503".)

The documentation for NATIVELSBSTRING perhaps hasn't caught up with
recent changes in it's definition and usage. If you see "universal" it
means native recipes are being compiled against a version of glibc
distributed by the Yocto project rather than the version of glibc
provided by your host distro. It's the default approach in recent
versions of poky and has the advantage that native recipes are always
built against a known and up to date version of glibc. It also allows
sstate for native recipes to be shared between hosts with different
versions of glibc (which wasn't previously possible).

> Also how is the TARGET_FPU variable set?

The answer to the question "how is variable XXX set" is always the
same... "bitbake -e" will tell you :-)

The reason this variable changed compared to older versions of poky is
likely to be that your machine config uses the default value of
DEFAULTTUNE set by tune-cortexa8.inc. That's the recommended approach,
but it does mean your builds will follow any change in the default
value. ie you are seeing the result of:

  http://git.openembedded.org/openembedded-core/commit/?id=2b3ae58f5eaecc8474761c543ff5347aa0e3c4c8

If you don't like the new default and need to compile for softfloat
then your machine config should explicitly set DEFAULTTUNE.

> Could someone please shed some light on this.
>
> Thanks!
>
> Mit freundlichen Grüßen / Best Regards,
> Dhanush Keshava Reddy Soppahalli
> Mob: +4915216144064
>
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