Re: [PATCH v5 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

From: Christoph Hellwig
Date: Wed Dec 19 2018 - 09:51:30 EST

On Wed, Dec 19, 2018 at 05:18:35PM +0900, Tomasz Figa wrote:
> The existing code that deals with dma_alloc_attrs() without
> DMA_ATTR_NON_CONSISTENT would just call dma_get_sgtable_attrs() like
> here:

I know. And dma_get_sgtable_attrs is fundamentally flawed and we
need to kill this interface as it just can't worked with virtually
tagged cases. It is a prime example for an interface that looks
nice and simple but is plain wrong.