On Mon, Aug 01, 2016 at 09:57:33AM +0300, Haggai Eran wrote:

Allocate a CMB region to user-space as a DMA-BUF object.

NACK.  Absolutely no way we're going to export a low-level device
specific feature to userspace like that.  If you want to DMA to
the CMB do it from the kernel, and for that we'll need a proper
block device level API.