[PATCH] dma-buf: mmap support

[Alan Cox]

> How do you ensure that no device can do DMA on the buffer while it's mapped
> into user space in a noncoherent manner?

Why do we want to enforce that ? We provide the appropriate base service
but you need to know what you are doing. In reality a lot of use cases
are going to need far more than a simple kernel API could try and guess
coherency rules about.