From: Christoph Hellwig <hch@lst.de>
To: Jes Sorensen <jes@wildopensource.com>
Cc: jejb@steeleye.com, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 2/3] qla1280: user pci_map_single
Date: Fri, 18 Feb 2005 11:21:31 +0100 [thread overview]
Message-ID: <20050218102131.GA2941@lst.de> (raw)
In-Reply-To: <yq03bvunqr3.fsf@jaguar.mkp.net>
On Fri, Feb 18, 2005 at 04:48:00AM -0500, Jes Sorensen wrote:
> Christoph,
>
> When pci_map_page was originally introduced it was meant to deprecate
> pci_map_single, at least thats what my memory tells me.
No, it's for rather different uses. pci_map_page would be nice to get
rid of in favour of pci_map_sg OTOH..
> If pci_map_single is suddenly recommended again we can change it back
> to that, but I don't really see the gain.
it's a micro-speedup by avoiding totally useless address arithmetics.
You first convert a buffer to page + offset and then it needs to be
converted back, e.g. in include/asm-ia64/dma-mapping.h:
#define dma_map_page(dev, pg, off, size, dir) \
dma_map_single(dev, page_address(pg) + (off), (size), (dir))
(pci_map_page is mapped to dma_map_page)
next prev parent reply other threads:[~2005-02-18 10:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-10 16:00 [PATCH 2/3] qla1280: user pci_map_single Christoph Hellwig
2005-02-18 9:48 ` Jes Sorensen
2005-02-18 10:21 ` Christoph Hellwig [this message]
2005-02-25 13:48 ` Jes Sorensen
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