Map a page of the buffer object into kernel address space. the same restrictions as for kmap_atomic and friends apply.
void * dma_buf_kmap_atomic(struct dma_buf * dmabuf, unsigned long page_num);
dmabuf
[in] buffer to map page from.
page_num
[in] page in PAGE_SIZE units to map.
This call must always succeed, any necessary preparations that might fail need to be done in begin_cpu_access.