Should dma_map_single take the dma controller or its consumer as an argument?

[Russell King (Oracle)]

On Wed, Jun 28, 2023 at 06:57:35PM +0800, Li Chen wrote:
> Hi all,
> 
> I recently encountered an issue where the dma_mask was set in the DMA controller's driver, but the consumer peripheral driver didn't set its own dma_mask.

It should always take the device that is *actually* performing the DMA,
since that is the device that has restrictions on what addresses can be
accessed, etc.

Devices that "consume" the data from a DMA controller don't access
memory - they are merely the targets, and they can't on their own access
host memory. Therefore, their dma mask _should_ be irrelevant.

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