kernel: move source and build output to work-shared

commit 3b3f7e785e279 [kernel: Rearrange for 1.8] began the process of
moving the kernel source and build artefacts out of sstate control and
into a shared location.

This changed triggered some workflow issues, as well as bugs related
to the kernel source containing build output, and hence being dirty and
breaking kernel rebuilds.

To solve these issues, and to make it clear that the kernel is not under
sstate control, we move the source and build outputs to:

  work-shared/MACHINE/kernel-source
  work-shared/MACHINE/kernel-build-artifacts

Where kernel-build-artifacts is the kernel build output and
kernel-source is kept "pristine". The build-artifacts contain everything
that is required to build external modules against the kernel source,
and includes the defconfig, the kernel-abiversion, System.map files and
output from "make scripts".

External module builds should either pass O= on the command line, or
set KBUILD_OUTPUT to point to the build-artifacts. module-base.bbclass
takes care of setting KBUILD_OUTPUT, so most existing external module
recipes are transparently adapted to the new source/build layout.

recipes that depend on the kernel source must have a depedency on the
do_shared_workdir task:

 do_configure[depends] += "virtual/kernel:do_shared_workdir"

With this dependency added, the STAGING_KERNEL_DIR will be populated and
available to the rest of the build.

(From OE-Core rev: 6a1ff0e7eacef595738f2fed086986fd622ec32a)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index 7902bd7d01..d22e9e8efe 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -395,7 +395,8 @@ SDKPATHNATIVE = "${SDKPATH}/sysroots/${SDK_SYS}"
 ##################################################################
 
 OLDEST_KERNEL = "2.6.32"
-STAGING_KERNEL_DIR = "${STAGING_DIR_HOST}/usr/src/kernel"
+STAGING_KERNEL_DIR = "${TMPDIR}/work-shared/${MACHINE}/kernel-source"
+STAGING_KERNEL_BUILDDIR = "${TMPDIR}/work-shared/${MACHINE}/kernel-build-artifacts"
 
 ##################################################################
 # Specific image creation and rootfs population info.