Re: [PATCH rdma-core 01/17] Update rdma/ib_user_verbs.h

[Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>]

On Mon, Jan 15, 2018 at 07:01:13PM +0200, Yishai Hadas wrote:
> On 1/12/2018 12:13 AM, Jason Gunthorpe wrote:
> >From: Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> >To let us use definitions from the latest kernel headers in followup
> >patches.
> >
> > From v4.15-rc7
> >
> >Signed-off-by: Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >  buildlib/RDMA_LinuxHeaders.cmake            |    2 +-
> >  buildlib/fixup-include/rdma-ib_user_verbs.h | 1176 +++++++++++++++++++++++++++
> >  2 files changed, 1177 insertions(+), 1 deletion(-)
> >  create mode 100644 buildlib/fixup-include/rdma-ib_user_verbs.h
> >
> >diff --git a/buildlib/RDMA_LinuxHeaders.cmake b/buildlib/RDMA_LinuxHeaders.cmake
> >index ea60b9b55844ea..aa2a89a53d0c2d 100644
> >+++ b/buildlib/RDMA_LinuxHeaders.cmake
> >@@ -86,7 +86,7 @@ function(rdma_report_missing_kheaders)
> >  endfunction()
> >  # This list is topologically sorted
> >-rdma_check_kheader("rdma/ib_user_verbs.h" "${DEFAULT_TEST}" NO_SHIM OPTIONAL)
> >+rdma_check_kheader("rdma/ib_user_verbs.h" "int main(int argc,const char *argv[]) { return IB_USER_VERBS_EX_CMD_MODIFY_CQ; }")
> 
> Any future change in this kernel header will require a change in this check
> as well and also a commit into fixup-include/rdma-ib_user_verbs.h with the
> new kernel code, correct ?

Yes.

> How will people be aware of that and won't miss it ? can we have some script
> that will warn/suggest the expected change upon a kernel change ?

Keeping the header up to date is not a big problem, there is no way to
get new symbols otherwise so people patching in new features have to
do it.

travis always does compiles using these headers as well.

Keeping the check quoted above broadly correct is more difficult. I
can't think of how to automate that, other than to manually inspect
patches that update the header to make sure they update the check as
well.

We could also switch to a more iproute like model where we just
unconditionally use our copies of the kernel headers..

Jason
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