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

[Shuah Khan]

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

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@xxxxxxxxxxxxxxx | (970) 217-8978
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