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

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Date:	Tue, 31 Mar 2015 17:53:10 -0400
From:	Waiman Long <waiman.long@...com>
To:	Shuah Khan <shuahkh@....samsung.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH] lfsr: a simple binary Galois linear feedback shift register

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@...com>
>> ---
>>   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.

Thanks,
Longman
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