linux-kernel - Re: [PATCH v3 3/3] b43: Use cordic algorithm from kernel library

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Message-ID: <fe3efdcb-3488-2fa5-f749-3e7366609697@lwfinger.net>
Date:   Mon, 19 Nov 2018 11:40:22 -0600
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Priit Laes <plaes@...es.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Jia-Ju Bai <baijiaju1990@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Colin Ian King <colin.king@...onical.com>,
        Arend van Spriel <arend.vanspriel@...adcom.com>,
        Varsha Rao <rvarsha016@...il.com>,
        linux-wireless@...r.kernel.org, b43-dev@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] b43: Use cordic algorithm from kernel library

On 11/19/18 5:27 AM, Priit Laes wrote:
> On Sun, Nov 18, 2018 at 01:35:57PM -0600, Larry Finger wrote:
>> On 11/18/18 2:23 AM, Priit Laes wrote:
>>> On Sat, Nov 17, 2018 at 09:31:35PM -0600, Larry Finger wrote:
>>>> On 11/14/18 12:27 PM, Priit Laes wrote:
>>>>> Kernel library has a common cordic algorithm which is identical
>>>>> to internally implementatd one, so use it and drop the duplicate
>>>>> implementation.
>>>>>
>>
>> My test setup has a hardware failure, thus I cannot test your patch, but I
>> now believe it to be correct. Thus your first and third patches may be
>> annotated with
>> ACKed-by: Larry Finger <Larry.Finger@...inger.net>
>>
>> One thing that should be done is to fix the error in the b43 code for stable
>> as it was introduced in 2.6.34. I propose adding the attached patched to
>> your series placed between your current 2nd and 3rd patches so that the old
>> kernels get fixed. Of course, your 3rd patch will need to be revised. If all
>> 4 of the patches get submitted together there will be no problems with the
>> timing. My change will exist for seconds in the mainline kernel, but it will
>> get propagated back through stable.
> 
> Thanks!
> 
>>  From b42ae73ef7505de93e4c66fb9f66930e3f3d969a Mon Sep 17 00:00:00 2001
>> From: Larry Finger <Larry.Finger@...inger.net>
>> Date: Sun, 18 Nov 2018 13:15:07 -0600
>> Subject: [PATCH] b43: Fix error in cordic routine
>> MIME-Version: 1.0
>> Content-Type: text/plain; charset=UTF-8
>> Content-Transfer-Encoding: 8bit
>> To: kvalo@...eaurora.org
>> Cc: linux-wireless@...r.kernel.org
>>
>> The cordic routine for calculating sines and cosines that was added in
>> commit 986504540306 ("b43: make cordic common (LP-PHY and N-PHY need it)")
>> contains an error whereby a quantity declared u32 can in fact go negative.
> 
> It seems to be different commit though:
> commit 6f98e62a9 ("b43: update cordic code to match current specs")

Thanks for catching that mistake. I must have gotten one line off in my copy and 
paste. The respun version of my patch is attached.

I have now been able to test b43 on an LP-PHY device. I do not see any major 
changes, but there has to be some effect.

Larry
Larry


View attachment "0001-b43-Fix-error-in-cordic-routine.patch" of type "text/x-patch" (1531 bytes)