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    SubjectRe: [PATCH] usb/mcs7830: Don't use buffers from stack for USB transfers
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    From: Arnd Bergmann <arnd@arndb.de>
    Date: Tue, 20 Jan 2009 23:45:47 +0100

    > On Tuesday 20 January 2009, you wrote:
    > > From: Christian Eggers <christian.eggers@kathrein.de>
    > >
    > > mcs7830_set_reg() and mcs7830_get_reg() are called with buffers
    > > from stack which must not be used directly for USB transfers.
    > > This causes corruption of the stack particulary on non x86
    > > architectures because DMA may be used for these transfers.
    > >
    > > Signed-off-by: Christian Eggers <christian.eggers@kathrein.de>
    >
    > Have you observed problems with this, or just suspected trouble?

    Yes, this is in response to SH platform failures.

    You cannot DMA from/to the kernel stack, because it might not be in
    the aliased linear mapping of physical memory. It could even be
    vmalloc()'d memory on some platforms.


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