drivers/base/dmapool.c: In function `pool_alloc_page': drivers/base/dmapool.c:171: warning: implicit declaration of function `dma_alloc_coherent' drivers/base/dmapool.c:174: warning: assignment makes pointer from integer without a cast drivers/base/dmapool.c: In function `pool_free_page': drivers/base/dmapool.c:209: warning: implicit declaration of function `dma_free_coherent' drivers/built-in.o(.text+0xe968): In function `pool_alloc_page': : undefined reference to `dma_alloc_coherent' drivers/built-in.o(.text+0xea2c): In function `pool_free_page': : undefined reference to `dma_free_coherent' make: *** [vmlinux] Error 1