On Tue, Feb 22, 2022 at 09:42:22PM +0800, Baoquan He wrote:

In the old dma mapping, coherent mapping uses dma_alloc_coherent() to
allocate DMA buffer and mapping; while streaming mapping can only get
memory from slab or buddy allocator, then map with dma_map_single().
In that situation, dma_alloc_direct() checks a direct mapping for
coherent DMA, dma_map_direct() checks a direct mapping for streaming
DMA.

However, several new APIs have been added for streaming mapping, e.g
dma_alloc_pages(). These new APIs take care of DMA buffer allocating
and mapping which are similar with dma_alloc_coherent(). So we should
rename both of them to reflect their real intention to avoid confusion.

       dma_alloc_direct()  ==>  dma_coherent_direct()
       dma_map_direct()    ==>  dma_streaming_direct()

No, these new names are highly misleading.