Memory Management Helpers

copy_to_user_fromio — copy data from mmio-space to user-space
copy_from_user_toio — copy data from user-space to mmio-space
snd_malloc_pages — allocate pages with the given size
snd_free_pages — release the pages
snd_dma_alloc_pages — allocate the buffer area according to the given type
snd_dma_alloc_pages_fallback — allocate the buffer area according to the given type with fallback
snd_dma_free_pages — release the allocated buffer