Date: Fri, 5 Oct 2007 15:24:50 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: schwab@suse.de, rpjday@mindspring.com, bbpetkov@yahoo.de,
       linux-kernel@vger.kernel.org, muli@il.ibm.com, satyam@infradead.org,
       amitkale@netxen.com, achim_leubner@adaptec.com
Subject: Re: [PATCH 1/1] unify DMA_..BIT_MASK definitions: v3.1
Message-Id: <20071005152450.a7652b75.akpm@linux-foundation.org>
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On Fri, 05 Oct 2007 14:28:45 -0700
Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Andreas Schwab wrote:
> > #define DMA_BIT_MASK(n)         ((u64)-1 >> (64 - (n)))
> >   
> 
> Yeah, that's cleaner.
> 

Well yes, but DMA_BIT_MASK(0) invokes undefined behaviour, generates a
compiler warning and evaluates to 0xffffffffffffffff (with my setup).

That won't be a problem in practice, but it is strictly wrong and doesn't set
a good exmaple for the children ;)

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