netdev - Re: [PATCH] net/dsa: remove unused macros to tame gcc warning

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Date:   Sat, 7 Nov 2020 23:33:01 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Joe Perches <joe@...ches.com>
Cc:     Alex Shi <alex.shi@...ux.alibaba.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/dsa: remove unused macros to tame gcc warning

On Sat, Nov 07, 2020 at 09:39:42AM -0800, Joe Perches wrote:
> On Sat, 2020-11-07 at 20:54 +0800, Alex Shi wrote:
> > 在 2020/11/7 上午12:39, Florian Fainelli 写道:
> > > > It is good to remember that there are multiple readers of source
> > > > files. There is the compiler which generates code from it, and there
> > > > is the human trying to understand what is going on, what the hardware
> > > > can do, how we could maybe extend the code in the future to make use
> > > > of bits are currently don't, etc.
> > > > 
> > > > The compiler has no use of these macros, at the moment. But i as a
> > > > human do. It is valuable documentation, given that there is no open
> > > > datasheet for this hardware.
> > > > 
> > > > I would say these warnings are bogus, and the code should be left
> > > > alone.
> > > Agreed, these definitions are intended to document what the hardware
> > > does. These warnings are getting too far.
> > 
> > Thanks for all comments! I agree these info are much meaningful.
> > Is there other way to tame the gcc warning? like put them into a .h file
> > or covered by comments?
> 
> Does _any_ version of gcc have this warning on by default?
> 
> I still think my proposal of moving the warning from W=2 to W=3
> quite reasonable.
> 
> Another possibility is to turn the warning off altogether.

Lets tern the question around first. How many real bugs have you found
with this warning? Places where the #define should of been used, but
was not? Then we can get an idea of the value of this warning. My
guess would be, its value is ~ 0 for the kernel. If so, we should just
turn it off.

     Andrew