[PATCH] drm/gem: Add new flink_to ioctl

[Alan Cox]

> > My argument was based around that the current system is designed as a
> > directory of opaque objects and so the extended attributes should be
> > kept opaque to the kernel as well and left open to interpretation by
> > userland. What I am most unclear about is under which circumstances is
> > this backchannel communication preferable to passing the extra information
> > over the IPC that needs to be performed anyway in order to open a surface.
> 
> That's the part I had trouble with as well.  Passing the blob through
> the kernel saves a little IPC but also seems unnecessary, and so rubs
> against my kernel minimalist side...

Passing the blob through the kernel does give you a basis for more
complex security since you can agree a blob format with the kernel
security layer and add security hooks to the interface in future.