Hi Christoph On Tue, 3 Dec 2019 05:06:09 -0800 Christoph Hellwig wrote: > > On Tue, Dec 03, 2019 at 09:49:49AM +0000, Jisheng Zhang wrote: > > > As in exactly one boundary and not an alignment? Where the one > > > boundary is not a power of two and thus can't be expressed? > > > > Take drivers/mmc/host/sdhci-of-dwcmshc.c for example, target physical DMA addr > > can't span 128MB, 256MB, 128*3MB, ...128*nMB > > > > I'm not sure whether blk_queue_segment_boundary could solve this limitation. > > That is exaxtly the kind of limitation blk_queue_segment_boundary is > intended for. Until after dma_map_sg(), we can't know the physical DMA address range, so how does block layer know and check the DMA range beforehand? I'm a newbie on block layer, could you please teach me? At the same time I'm reading the code as well. Thanks in advance
