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    SubjectRe: USB transfer_buffer allocations on 64bit systems
    At Wed, 7 Apr 2010 18:16:03 +0200,
    Daniel Mack wrote:
    >
    > On Wed, Apr 07, 2010 at 11:55:19AM -0400, Alan Stern wrote:
    > > On Wed, 7 Apr 2010, Greg KH wrote:
    > >
    > > > Alan, any objection to just using usb_buffer_alloc() for every driver?
    > > > Or is that too much overhead?
    > >
    > > I don't know what the overhead is. But usb_buffer_alloc() requires the
    > > caller to keep track of the buffer's DMA address, so it's not a simple
    > > plug-in replacement. In addition, the consistent memory that
    > > usb_buffer_alloc() provides is a scarce resource on some platforms.
    > >
    > > Writing new functions is the way to go.
    >
    > Ok, I'll write some dummies for usb_malloc() and usb_zalloc() which
    > will just call kmalloc() with GFP_DMA32 for now.

    Can't we provide only zalloc() variant? Zero'ing doesn't cost much,
    and the buffer allocation shouldn't be called too often.

    > And while at it,
    > usb_alloc_buffer() will be renamed to usb_alloc_consistent().

    Most of recent functions are named with "coherent".


    thanks,

    Takashi


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