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    Subjectpci_alloc_consistent from interrupt == BAD
    Somehow the docs in DMA-mappings.txt say pci_alloc_consistent is allowed from 
    interrupt, but this is a "bad thing" on at least arm and PPC non-cache
    coherent cpus.

    On these cpus we have to allocate page tables for consistent_alloc.. I really
    dont' think we want to be doing this during interrupt context.

    This also causes the sym53c8xx_2 driver to not work on some embedded ppc 4xx
    boards, and in general, seems to be a 'bad thing' to allow.

    For example, in the arch/arm/consistent.c:

    * This allocates one page of cache-coherent memory space and returns
    * both the virtual and a "dma" address to that space. It is not clear
    * whether this could be called from an interrupt context or not. For
    * now, we expressly forbid it, especially as some of the stuff we do
    * here is not interrupt context safe.
    * Note that this does *not* zero the allocated area!
    void *consistent_alloc(int gfp, size_t size, dma_addr_t *dma_handle)

    (arm's pci_alloc_consistent always calls consistent_alloc).

    The PPC version calls a similiar function when CONFIG_NOT_COHERENT_CACHE is
    defined. On 'regular' ppc machines, it's just a __get_free_pages, which is
    why no one from the pmac crowd has screamed.

    Troy Benjegerdes | master of mispeeling | 'da hozer' |
    -----"If this message isn't misspelled, I didn't write it" -- Me -----
    "Why do musicians compose symphonies and poets write poems? They do it
    because life wouldn't have any meaning for them if they didn't. That's
    why I draw cartoons. It's my life." -- Charles Schulz
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