linux-kernel - Re: Clang warning in drivers/net/ethernet/intel/igc/igc

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Date:   Fri, 1 Mar 2019 10:28:35 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     netdev@...r.kernel.org,
        Nathan Chancellor <natechancellor@...il.com>,
        Sasha Neftin <sasha.neftin@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Aaron Brown <aaron.f.brown@...el.com>,
        intel-wired-lan@...ts.osuosl.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Clang warning in drivers/net/ethernet/intel/igc/igc_ethtool.c

On Fri, Feb 8, 2019 at 6:34 AM Michal Kubecek <mkubecek@...e.cz> wrote:
>
> On Thu, Feb 07, 2019 at 10:09:21PM -0700, Nathan Chancellor wrote:
> > Hi all,
> >
> > After commit 8c5ad0dae93c ("igc: Add ethtool support"), Clang warns:
> >
> > drivers/net/ethernet/intel/igc/igc_ethtool.c:9:19: warning: variable 'igc_priv_flags_strings' is not needed and will not be emitted [-Wunneeded-internal-declaration]
> > static const char igc_priv_flags_strings[][ETH_GSTRING_LEN] = {
> >                   ^
> > 1 warning generated.
> >
> > igc_priv_flags_strings is only used in an ARRAY_SIZE macro, which is a
> > compile time evaluation, so no reference to it is being emitted in the
> > final assembly. Is it actually needed and was forgotten to be used
> > somewhere or could it be eliminated so that Clang no longer warns?
>
> That's because the driver provides get_priv_flags() and set_priv_flags()
> callbacks in its ethtool_ops to allow querying and setting legacy-rx
> private flag but it does not provide get_sset_count() and get_strings()
> to provide list of private flags to userspace ethtool.

So the variable declaration should get a `__unused` annotation then
(and maybe a comment)?

-- 
Thanks,
~Nick Desaulniers