Re: [PATCH 3/4] dma-buf: add support for mapping with dma mapping attributes

[Laura Abbott]

On 1/19/19 2:25 AM, Christoph Hellwig wrote:
> On Fri, Jan 18, 2019 at 10:37:46AM -0800, Liam Mark wrote:
> > Add support for configuring dma mapping attributes when mapping
> > and unmapping memory through dma_buf_map_attachment and
> > dma_buf_unmap_attachment.
> >
> > Signed-off-by: Liam Mark <lmark@xxxxxxxxxxxxxx>
>
> And who is going to decide which ones to pass?  And who documents
> which ones are safe?
>
> I'd much rather have explicit, well documented dma-buf flags that
> might get translated to the DMA API flags, which are not error checked,
> not very well documented and way to easy to get wrong.

I'm not sure having flags in dma-buf really solves anything
given drivers can use the attributes directly with dma_map
anyway, which is what we're looking to do. The intention
is for the driver creating the dma_buf attachment to have
the knowledge of which flags to use.

Thanks,
Laura