virt_to_page/pci_map_page vs. pci_map_single

From: Jamie Wellnitz (Jamie.Wellnitz_at_emulex.com)
Date: 11/02/03

  • Next message: Jose Luis Domingo Lopez: "Re: Bkbits down?" 
    Date:	Sun, 2 Nov 2003 13:12:24 -0500
To: linux-kernel@vger.kernel.org

    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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  • Next message: Jose Luis Domingo Lopez: "Re: Bkbits down?"

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