netdev - Re: sfc: an enumeration is not a bitmask

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Message-ID: <BANLkTinaO0VVGpRRqRauH6FucvwbcXyRUg@mail.gmail.com>
Date:	Tue, 17 May 2011 21:09:34 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Jeff Garzik <jgarzik@...ox.com>
Cc:	David Miller <davem@...emloft.net>, bhutchings@...arflare.com,
	netdev@...r.kernel.org
Subject: Re: sfc: an enumeration is not a bitmask

2011/5/17 Jeff Garzik <jgarzik@...ox.com>:
> 2011/5/17 David Miller <davem@...emloft.net>:
>> An enumeration is not a bitmask, instead it means one out of the set
>> of enumerated values will be used.
>
> It's a decade-old kernel practice to use 'enum' to define typed
> constants, preferred over  macros that convey no type information and
> disappear after cpp phase.
>
> So your assertion about enumerations is demonstrably not true, as it
> is often used in the kernel.  Call it enum abuse if you want, but it
> is consistent with code all over the kernel.
>
> That said, I agree that warnings should of course be addressed in some manner.

Old age of the mistake doesn't make it correct.

Disappearance of the #defines can be resolved by using enum of bit
positions (and maybe field lengths) and #define of (1 << bit_position)
if it is useful for something to remain after preprocessing.

Best Regards,
Michał Mirosław
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