Re: [PATCH] lfsr: a simple binary Galois linear feedback shift register

[Waiman Long]

On 03/31/2015 05:58 PM, Shuah Khan wrote:
> On 03/31/2015 03:53 PM, Waiman Long wrote:
> > On 03/31/2015 03:21 PM, Shuah Khan wrote:
> > > On 03/31/2015 11:28 AM, Waiman Long wrote:
> > > > This patch is based on the code sent out by Peter Zijstra as part
> > > > of his queue spinlock patch to provide a hashing function with open
> > > > addressing.  The lfsr() function can be used to return a sequence of
> > > > numbers that cycle through all the bit patterns (2^n -1) of a given
> > > > bit width n except the value 0 in a somewhat random fashion depending
> > > > on the LFSR tap that is being used.
> > > Does this new test intended to test a new kernel feature? If so could
> > > you please include what it tests in the commit log. It isn't very clear
> > > to me what this test does?
> > This test is for checking the correctness of the lfsr.h header file. I
> > will clarify that in the commit log.
> >
> > > > This code should be a standalone patch and not part of a larger
> > > > patch series.  I have also modified and extended it and added some
> > > > testing code to verify the correctness of the taps that are being used.
> > > The above can be left out of the commit log.
> > Sure.
> >
> > > > Signed-off-by: Waiman Long<Waiman.Long@xxxxxx>
> > > > ---
> > > >    include/linux/lfsr.h                     |   84
> > > > ++++++++++++++++++++++++++++++
> > > >    tools/testing/selftests/lfsr/Makefile    |   11 ++++
> > > >    tools/testing/selftests/lfsr/test-lfsr.c |   70
> > > > +++++++++++++++++++++++++
> > > >    3 files changed, 165 insertions(+), 0 deletions(-)
> > > >    create mode 100644 include/linux/lfsr.h
> > > >    create mode 100644 tools/testing/selftests/lfsr/Makefile
> > > >    create mode 100644 tools/testing/selftests/lfsr/test-lfsr.c
> > > I don't see the test added to selftests/Makefile? Is it the intent
> > > to leave it out of default test run and install? If this test
> > > is intended to be part of selftests run and install, please add
> > > it to selftests Makefile and also add install target support.
> > > You can find good examples in linux-kselftest next branch.
> > > Please add a .gitignore for git to ignore the binaries built.
> > >
> > > thanks,
> > > -- Shuah
> > Yes, it is intended to be left out of the default selftest run and
> > install because the lfsr.h header is for kernel internal use and is not
> > accessible from any of the kernel syscall APIs.
> Please add this to the commit log as well that it shouldn't be included
> in the default run and install. Also BUG_ON and BUILD_BUG_ON are used
> in this test. These are kernel defines, hope these are included somehow.
>
> -- Shuah

I will update the patch once I receive feedbacks from others. The lfsr.h 
header does use BUG_ON and BUILD_BUG_ON, but they are disabled in the 
self-test.

-Longman
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