cache maintenance for device memory

[Random Guy]

On Thu, Dec 3, 2015 at 1:29 PM, Random Guy
<random.guy.from.russia at gmail.com> wrote:
> I have a device with a piece of RAM. That memory is accessible to CPU.
> I write a driver for that device and it maps device memory directly to
> userspace processes. This mapping is cacheable. So far so good.

Ok, I did some research and all drivers that I've found that map memory
to userspace do it with caching disabled.

After some more reading, especially
  http://events.linuxfoundation.org/sites/events/files/slides/20140429-dma.pdf
I conclude that cacheable mapping of device memory to userspace is
not supported in linux at all.

Is that correct?

TIA