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Date: Sun, 24 May 2009 00:59:26 +0200
Message-ID: <c384c5ea0905231559i5ffb0637te62ee005074f9435@mail.gmail.com>
Subject: Re: [PATCH V2 2/3] powerpc: Add support for swiotlb on 32-bit
From: Leon Woestenberg <leon.woestenberg@gmail.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
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Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>,
	FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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Hello,

On Sat, May 23, 2009 at 1:55 AM, Jeremy Fitzhardinge <jeremy@goop.org> wrot=
e:
> Ian Campbell wrote:
>>
>> On Thu, 2009-05-21 at 14:27 -0400, Becky Bruce wrote:
>>
>>>
>>> I can work with that, but it's going to be a bit inefficient, as I
>>> =A0actually need the dma_addr_t, not the phys_addr_t, so I'll have to
>>> =A0convert. =A0In every case, this is a conversion I've already done an=
d =A0that I
>>> need in the calling code as well.
>>
>> Does
>>
>> =A0 =A0dma_addr_t dma_map_range(struct device *hwdev, phys_addr_t addr,
>> =A0 =A0size_t size);
>>
>> work for you?
>>
>> If the range does not need mapping then it returns the dma address, if
>> you needed to calculate the dma address anyway to figure out if mapping
>> is required then this is fine. If the range does need mapping then it
>> returns NULL.
>>
>
> My only concern is whether dma_addr_t =3D=3D 0 is actually equivalent to =
NULL.
> =A0That is, can we be sure that address 0 will never be used?
>
Indeed, I remember seeing 0 returned on pci_alloc_coherent() as an
address (cookie).

Regards,
--=20
Leon