On 00:12 Tue 29 Jan , Peter Teoh wrote:
> what is the difference between get_free_page()/kmem_cache_alloc() and
> vmalloc() that makes the former dma-able, and latter not?
vmalloc does *not* allocate physical pages. It allocates virtual pages that are
accessed via the MMU - in cases where you have to allocate larger amounts of
memory in the kernel. The device that wants to DMA this memory does not have an
MMU. So the access fails - except you make the page table lookup yourself
send the underlying physical address to the device instead.
-Michi
--
programing a layer 3+4 network protocol for mesh networks
see http://michaelblizek.homelinux.net
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