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

[Christoph Hellwig]

Folks, can you take a look at this tree and see if this is useful
for USB:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-noncoherent-allocator

The idea is that you use dma_alloc_attrs with the DMA_ATTR_NON_CONSISTENT
now that I've made sure it is avaiable everywhere [1], and we can use
dma_sync_single_* on it.

The only special case USB will need are the HCD_LOCAL_MEM devices, for
which we must use dma_alloc_coherent (or dma_alloc_attrs without
DMA_ATTR_NON_CONSISTENT) and must skip the dma_sync_single_* calls,
so we'll probably need USB subsystem wrappers for those calls.

[1] except powerpc in this tree - I have another series to make powerpc
use the generic dma noncoherent code, which would cover it.