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From: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Date: Thu, 13 Sep 2012 16:56:04 +0100
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        <linux-kernel@vger.kernel.org>, <xen-devel@lists.xensource.com>,
        <stefano.stabellini@eu.citrix.com>
Subject: Re: [Xen-devel] [PATCH 09/10] xen/swiotlb: Fix compile warnings when
	using plain integer instead of NULL pointer.
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Ian Jackson writes ("Re: [Xen-devel] [PATCH 09/10] xen/swiotlb: Fix compile warnings when using plain integer instead of NULL pointer."):
> Konrad Rzeszutek Wilk writes ("[Xen-devel] [PATCH 09/10] xen/swiotlb: Fix compile warnings when using plain integer instead of NULL pointer."):
> > arch/x86/xen/pci-swiotlb-xen.c:96:1: warning: Using plain integer as NULL pointer
> > arch/x86/xen/pci-swiotlb-xen.c:96:1: warning: Using plain integer as NULL pointer
> 
> This warning is simply wrong for this code:
> 
> >  IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
> > -		  0,
> > +		  NULL,
> 
> There is (according to the C language specifications) nothing wrong
> with writing 0 for a null pointer.
> 
> Nor does CODING_STYLE say that it is forbidden to just write 0.

Oh wait this is Linux kernel code, not in Xen?  Still,
Documentation/CodingStyle doesn't say that NULL is required.

Ian.