linux-kernel - Re: PATCH[[vme/bridges/vme_ca91cx42.c:1382: Bad if test Bug Fix]‏‏

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Message-ID: <539EC21E.8030909@ge.com>
Date:	Mon, 16 Jun 2014 11:08:30 +0100
From:	Martyn Welch <martyn.welch@...com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	nick <nickkrause@...patico.ca>, <manohar.vanga@...il.com>,
	<gregkh@...uxfoundation.org>, <devel@...verdev.osuosl.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: PATCH[[vme/bridges/vme_ca91cx42.c:1382: Bad if test Bug Fix]‏‏

On 16/06/14 10:56, Dan Carpenter wrote:
> On Mon, Jun 16, 2014 at 10:47:25AM +0100, Martyn Welch wrote:
>> Nick,
>>
>> Sorry for the delay in responding.
>>
>> I'm staring at the manual for the ca91c142 and the relevant bits in
>> the VSIx_CTL registers definitely need to be set to 0 for A16,
>> likewise with the LM_CTL register. The pattern (3<<16) would enable
>> one of the "reserved" address spaces.
>>
>
> Nick emailed me privately that this was a static checker warning.  These
> warnings are often false positives...  But I'm worried about the test:
>
> 	if ((ctl & CA91CX42_VSI_CTL_VAS_M) == CA91CX42_VSI_CTL_VAS_A16)
> 		*aspace = VME_A16;
>
> That could be true when we didn't intend it.
>

If I'm not mistaken, CA91CX42_VSI_CTL_VAS_A16 is currently defined as 0.

So:
	if ((ctl & (7<<16) == 0)
		*aspace = VME_A16;

Which looks right to me, it's checking to see if the relevant bits in 
the register are all zero, am I missing something obvious?

Martyn


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