[PATCH v3 05/10] lib: add dmabuf token infrastructure

[Christoph Hellwig]

Naming and placement:

This is about dma-buf based I/O.  So I'd expect it to be named dma-buf-io
and no io-dmabuf, and live in drivers/dma-buf and not the unrelated lib/.
But I'd like to hear from the dma-buf maintainers about that.

Config option:  as this unconditionally when DMA_SHARED_BUFFER is enabled,
why does it need a separate config option?

Interface:  io_dmabuf_token_create / ->create_dmabuf_token filling
in a structure allocated by the caller feels odd.  My gut feeling
would be to move most of io_dmabuf_token_create into a helper called
by ->create_dmabuf_token so that the token is allocated in the
driver data structure and returned from create_dmabuf_token.