linux-kernel - Re: [PATCH v3] net: stmmac: compare p->des0 and p->des1 with _

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Message-ID: <20230519210439.4a3bb326@kernel.org>
Date:   Fri, 19 May 2023 21:04:39 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Min-Hua Chen <minhuadotchen@...il.com>
Cc:     alexandre.torgue@...s.st.com, davem@...emloft.net,
        edumazet@...gle.com, joabreu@...opsys.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        mcoquelin.stm32@...il.com, netdev@...r.kernel.org,
        pabeni@...hat.com, peppe.cavallaro@...com,
        simon.horman@...igine.com
Subject: Re: [PATCH v3] net: stmmac: compare p->des0 and p->des1 with __le32
 type values

On Sat, 20 May 2023 09:55:27 +0800 Min-Hua Chen wrote:
> >Can you try to fix the sparse tool instead? I believe it already
> >ignores such errors for the constant of 0, maybe it can be taught 
> >to ignore all "isomorphic" values?
> >  
> 
> I downloaded the source code of sparse and I'm afraid that I cannot make
> 0xFFFFFFFF ignored easily. I've tried ~0 instead of 0xFFFFFF,
> but it did not work with current sparse.
> 
> 0 is a special case mentioned in [1].
> 
> """
> One small note: the constant integer “0” is special. 
> You can use a constant zero as a bitwise integer type without
> sparse ever complaining. This is because “bitwise” (as the name
> implies) was designed for making sure that bitwise types don’t
> get mixed up (little-endian vs big-endian vs cpu-endian vs whatever),
> and there the constant “0” really _is_ special.
> """
> 
> For 0xFFFFFFFF, it may look like a false alarm, but we can silence the
> sparse warning by taking a fix like mine and people can keep working on
> other sparse warnings easier.

We can make working with sparse easier by making sure it doesn't
generate false positive warnings :\

> (There are around 7000 sparse warning in ARCH=arm64 defconfig build and
> sometimes it is hard to remember all the false alarm cases)
> 
> Could you consider taking this patch, please?

No. We don't take patches to address false positive static 
checker warnings.