dma buf sharing between multiple processes

Question

I am trying to understand the dma buf framework in linux kernel and going through this article http://lwn.net/Articles/489703/ which says

Userspace entity requests for a file-descriptor (fd) which is a handle to the anonymous file associated with the buffer. It can then share the fd with other drivers and/or processes.

My question is, "any fd allocated is unique to a process. so, i think if we pass this to another process(passed fd is invalid in this process context) how can it get the handle to dma buffer?"

Answer 1

The way it works is that you have to use a special fd-sharing mechanism like unix domain sockets or binder.