Integration with dma_buf

When we discussed the design for dma_buf, it was intentionally made possible to have arbitrary subsystems provide interfaces that hand out dma_buf file descriptors to user space, although the focus so far was on having drm provide descriptors for buffers that it already manages. If I understand the article correctly, the design of ion is that you always have to know in advance how to allocate your buffer through the ion ioctl but then can pass it into any driver using it.

We should probably look into unifying the in-kernel interfaces for the two, because they are already very similar. and make ION_IOC_SHARE return a dma_buf descriptor that can be passed into any dma_buf enabled driver. The ion_import_fd function can then be replaced with the more abstract dma_buf equivalent.