Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device

On Mon, Mar 23, 2020 at 09:07:38PM +0530, Aneesh Kumar K.V wrote:

This is what I was trying, but considering I am new to DMA subsystem, I
am not sure I got all the details correct. The idea is to look at the
cpu addr and see if that can be used in direct map fashion(is
bus_dma_limit the right restriction here?) if not fallback to dynamic
IOMMU mapping.

I don't think we can throw all these complications into the dma
mapping code.  At some point I also wonder what the point is,
especially for scatterlist mappings, where the iommu can coalesce.