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    SubjectRe: USB mass storage and ARM cache coherency
    On Mon, Feb 01, 2010 at 03:14:04PM -0500, Alan Stern wrote:
    > On Mon, 1 Feb 2010, Catalin Marinas wrote:
    >
    > > On Fri, 2010-01-29 at 18:54 +0000, Matthew Dharm wrote:
    > > > HOWEVER, I firmly believe that the cache-management functions belong with
    > > > the driver that actually talks to the low-level hardware, as that's the
    > > > only place where you can be 100% certain of what cache operations are
    > > > needed. After all, I think someone is working on a USB-over-IP transport,
    > > > and trying to manage cache at the usb-storage level in that scenario is
    > > > just silly.
    > > >
    > > > So, let's put this in the HCD drivers and be done with it.
    > >
    > > The patch below is what fixes the I-D cache incoherency issues on ARM. I
    > > don't particularly like the solution but it seems to be the only one
    > > available.
    > >
    > > IMHO, Linux should have functions similar to the DMA API but for PIO
    > > drivers (e.g. pio_map_single/pio_unmap_single) that non-coherent
    > > architectures can define, otherwise being no-ops. Any thoughts?
    >
    > You should bring this up on the linux-arm-kernel mailing list and CC:
    > the ARM maintainer. They are the ones most directly affected.
    >
    No, this belongs on linux-arch, as it's something that impacts a lot of
    people besides ARM.


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