Re: [PATCH 0/4] Fix kselftest build with sub-directory

[Shuah Khan]

On 7/8/22 10:23 AM, Guillaume Tucker wrote:
> Earlier attempts to get "make O=build kselftest-all" to work were
> not successful as they made undesirable changes to some functions
> in the top-level Makefile.  This series takes a different
> approach by removing the root cause of the problem within
> kselftest, which is when the sub-Makefile tries to install kernel
> headers "backwards" by calling make with the top-level Makefile.
> The actual issue comes from the fact that $(srctree) is ".." when
> building in a sub-directory with "O=build" which then obviously
> makes "-C $(top_srcdir)" point outside of the real source tree.
>
> With this series, the generic kselftest targets work as expected
> from the top level with or without a build directory e.g.:
>
>    $ make kselftest-all
>
>    $ make O=build kselftest-all
>
> Then in order to build using the sub-Makefile explicitly, the
> headers have to be installed first.  This is arguably a valid
> requirement to have when building a tool from a sub-Makefile.
> For example, "make -C tools/testing/nvdimm/" fails in a similar
> way until <asm/rwonce.h> has been generated by a kernel build.
>
> Guillaume Tucker (4):
>    selftests: drop khdr make target
>    selftests: stop using KSFT_KHDR_INSTALL
>    selftests: drop KSFT_KHDR_INSTALL make target
>    Makefile: add headers_install to kselftest targets

This takes us to back to the state before b2d35fa5fc80 added
khdr support. I reluctantly agreed to the change and it has
proven to be a problematic change. I would rather have had the
dependency stated that headers should be installed prior to
building tests - test build depends on kernel build anyway and
having dependency on headers having build isn't a huge deal.

So I am in favor of getting rid of khdr support. However, this
khdr support was a change originated from Linaro test ring. Undoing
this might have implication on their workflow.

I will pull them into the discussion so they are aware of it and
be prepared for this change.

thanks,
-- Shuah