DRM ioctls are taking advantage of the fact that any ioctl structure
that is passed in to the kernel smaller than the expected value will
zero out the remaining members of the structure.
Some more ioctls coming down the pipe will also abuse this, so we might
as well as get started with the v3d ioctl that requires it.
Due to how this works, the kernel knows how big an ioctl structure
should be and if the userspace passes in a smaller struct, it will
memset the remaining size to zero.
Migrates lingering instances of the old logger over to fmt where
applicable. This allows removing some of the old defines and functions.
The only remaining usages of the printf-based variant of the logger is
in Tests/LinuxSyscalls/Syscalls.cpp for the strace handling.
For DRM applications have a three FD deep MRU cached for faster lookups of FD to DRM handlers.
In a completely DRM ioctl bound situation like es2gears or GL application without threaded context
Then this puts us /nearly/ at the performance of calling the ioctl32 handler directly.
Sadly there is overhead that can't be overcome so this is the best that can be done from userland
Ryan Houdek