From: Jamie Wellnitz <Jamie.Wellnitz@emulex.com>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Jes Sorensen <jes@wildopensource.com>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: virt_to_page/pci_map_page vs. pci_map_single
Date: Mon, 3 Nov 2003 17:03:35 -0500 [thread overview]
Message-ID: <20031103220335.GH18060@ma.emulex.com> (raw)
In-Reply-To: <1067885332.2076.13.camel@mulgrave>
On Mon, Nov 03, 2003 at 12:48:42PM -0600, James Bottomley wrote:
>
>
> Jamie> The Document/DMA-mapping.txt in 2.6.0-test9 says "To map a
> Jamie> single region, you do:" and then shows pci_map_single. Is
> Jamie> DMA-mapping.txt in need of patching?
>
> Sounds like it needs an update.
>
> Erm, I don't think so. pci_map_single() covers a different use case
> from pci_map_page().
>
> The thing pci_map_single() can do that pci_map_page() can't is cope with
> contiguous regions greater than PAGE_SIZE in length (which you get
> either from kmalloc() or __get_free_pages()). This feature is used in
> the SCSI layer for instance.
Does "pci_map_page(virt_to_page(addr))" handle contiguous regions of
multiple pages? It seems like the i386 implementation will (assuming
we're dealing with kmalloc'd memory). Although the semantics of
map_single seem better to me than map_page, if I'm mapping a single
"region" of multiple pages.
>
> There has been talk of deprecating dma_map_single() in favour of
> dma_map_sg() (i.e. make all transfers use scatter/gather and eliminate
> dma_map_single() in favour of a single sg entry table) but nothing has
> been done about it (at least as far as I know).
>
> James
Thanks,
Jamie Wellnitz
next prev parent reply other threads:[~2003-11-03 22:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-03 18:48 virt_to_page/pci_map_page vs. pci_map_single James Bottomley
2003-11-03 22:03 ` Jamie Wellnitz [this message]
2003-11-04 9:48 ` Jes Sorensen
2003-11-04 16:35 ` Matt Porter
2003-11-04 16:47 ` James Bottomley
2003-11-04 17:11 ` Matt Porter
2003-11-04 16:43 ` James Bottomley
2003-11-05 16:23 ` Anton Blanchard
2003-11-06 8:28 ` Jes Sorensen
[not found] <NuZH.1a5.7@gated-at.bofh.it>
[not found] ` <NI6s.1MM.3@gated-at.bofh.it>
[not found] ` <NMtC.7Vs.21@gated-at.bofh.it>
[not found] ` <NNSy.1Cd.1@gated-at.bofh.it>
[not found] ` <NV3O.5w7.19@gated-at.bofh.it>
[not found] ` <NWCA.7Qv.19@gated-at.bofh.it>
2003-11-04 8:41 ` Ihar 'Philips' Filipau
-- strict thread matches above, loose matches on Subject: below --
2003-11-02 18:12 Jamie Wellnitz
2003-11-03 8:10 ` Jes Sorensen
2003-11-03 12:52 ` Jamie Wellnitz
2003-11-03 14:17 ` Jes Sorensen
2003-11-03 22:02 ` David Mosberger
2003-11-04 0:41 ` David S. Miller
2003-11-04 9:44 ` Jes Sorensen
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