Hi! While porting on an old out-of-tree driver I noticed that dma_alloc_coherent() was used with dev being NULL.
commit 148a97d5a02a62f81b5d6176f871c94a65e1f3af Author: Dan Carpenter <[email protected]> Date: Wed Apr 24 17:24:37 2019 +0300 dma-mapping: remove an unnecessary NULL check We already dereferenced "dev" when we called get_dma_ops() so this NULL check is too late. We're not supposed to pass NULL "dev" pointers to dma_alloc_attrs(). Signed-off-by: Dan Carpenter <[email protected]> Signed-off-by: Christoph Hellwig <[email protected]> says that dma_alloc_attrs() with dev being NULL is not allowed, but in include/linux/dma-mapping.h we have: static inline void *dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp) { return dma_alloc_attrs(dev, size, dma_handle, gfp, (gfp & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0); } In Linus' tree I see at least three callers of dma_alloc_coherent() with a NULL device. drivers/staging/emxx_udc/emxx_udc.c:2596: ep->virt_buf = dma_alloc_coherent(NULL, PAGE_SIZE, drivers/tty/synclink.c:3667: info->buffer_list = dma_alloc_coherent(NULL, BUFFERLISTSIZE, &info->buffer_list_dma_addr, GFP_KERNEL); drivers/tty/synclink.c:3777: BufferList[i].virt_addr = dma_alloc_coherent(NULL, DMABUFFERSIZE, &BufferList[i].dma_addr, GFP_KERNEL); I think these callers are wrong. Can you please clarify? Thanks, //richard
