Date: Sun, 2 Nov 2003 13:12:24 -0500
From: Jamie Wellnitz <Jamie.Wellnitz@emulex.com>
To: linux-kernel@vger.kernel.org
Subject: virt_to_page/pci_map_page vs. pci_map_single
Message-ID: <20031102181224.GD2149@ma.emulex.com>
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I see code similar to the following in a few drivers (qlogicfc,
sym53c8xx, acenic does something similar):

page = virt_to_page(buffer);
offset = ((unsigned long)buffer & ~PAGE_MASK);
busaddr = pci_map_page(pci_dev, page, offset, len, direction);

How is this preferable to:

pci_map_single( pci_dev, buffer, len, direction);

?

pci_map_single can't handle highmem pages (because they don't have a
kernel virtual address) but doesn't virt_to_page suffer from the same
limitation?  Is there some benefit on architectures that don't have
highmem?

Thanks,
Jamie Wellnitz
Jamie.Wellnitz@emulex.com
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