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Segmentation > is intended to make the sgl entries map 1:1 to HW entries so the block > layer can schedule correctly. Yeah and that is a clear violation of the principle that kernel APIs shouldn't be designed with the use case in mind. Instead the API should reflect what the HW does and needs, e.g. in this case what the bus systems and IOMMU engines can or can't do. How it is used in the end should be irrelevant to that, it only servers as validation if the design fulfills all requirements or not. Regards, Christian. > > Nothing else needs something like this but still has to tip toe around > these rules. It makes it more complicated to map and then in some > cases you have to undo it when programming HW :\ > > Reviewed-by: Jason Gunthorpe > > Jason