Re: [PATCH v2] arm64: do not set dma masks that device connection can't handle

Christoph Hellwig
2017-01-10T14:51:13Z

On Tue, Jan 10, 2017 at 03:47:25PM +0300, Nikita Yushchenko wrote:
> With this direction, semantics of dma mask becomes even more
> questionable. I'd say dma_mask is candidate for removal (or to move to
> swiotlb's or iommu's local area)

We need the dma mask so that the device can advertise what addresses
the device supports. Many old devices only support 32-bit DMA addressing,
and some less common ones just 24-bit or other weird ones.