mm: add coherence API for DMA to vmalloc/vmap areas

	All the functionality of flush_icache_page can be implemented in

	flush_dcache_page and update_mmu_cache. In 2.7 the hope is to

	remove this interface completely.

The final category of APIs is for I/O to deliberately aliased address

ranges inside the kernel.  Such aliases are set up by use of the

vmap/vmalloc API.  Since kernel I/O goes via physical pages, the I/O

subsystem assumes that the user mapping and kernel offset mapping are

the only aliases.  This isn't true for vmap aliases, so anything in

the kernel trying to do I/O to vmap areas must manually manage

coherency.  It must do this by flushing the vmap range before doing

I/O and invalidating it after the I/O returns.

  void flush_kernel_vmap_range(void *vaddr, int size)

       flushes the kernel cache for a given virtual address range in

       the vmap area.  This is to make sure that any data the kernel

       modified in the vmap range is made visible to the physical

       page.  The design is to make this area safe to perform I/O on.

       Note that this API does *not* also flush the offset map alias

       of the area.

  void invalidate_kernel_vmap_range(void *vaddr, int size) invalidates

       the cache for a given virtual address range in the vmap area

       which prevents the processor from making the cache stale by

       speculatively reading data while the I/O was occurring to the

       physical pages.  This is only necessary for data reads into the

       vmap area.

static inline void flush_kernel_dcache_page(struct page *page)

{

}

static inline void flush_kernel_vmap_range(void *vaddr, int size)

{

}

static inline void invalidate_kernel_vmap_range(void *vaddr, int size)

{

}

#endif

#include <asm/kmap_types.h>