[PATCH v11 07/11] device-mapping: Introduce DMA range map, supplanting dma_pfn_offset

Christoph Hellwig hch at lst.de
Tue Sep 8 06:59:10 UTC 2020


On Mon, Sep 07, 2020 at 08:19:43PM +0200, Nicolas Saenz Julienne wrote:
> Indeed, that's why I wasn't all that happy with my solution.
> 
> As an alternative, how about returning '-dev->bus_dma_limit' instead of 0? It's
> always 0 for the devices without bus_dma_regions, and, I think, an always
> unattainable offset for devices that do (I tested it on RPi4 with the 30bit
> limitd mmc controller and it seems to work alright).

No, bus_dma_limit can be set independent of offsets.  We use it e.g.
to limit old x86 VIA PCI bridges to 32-bit addressing.


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