I/O Devices were meant to be handles of sorts and had a built in mpsc queue
as this made sense initially. As time has gone on it turned out that often
we wanted the mpsc queue to be an implementation detail hidden in a driver.
In fact pretty much all drivers work this way now.
Keeping the struct mpsc queue as a member of rtio_iodev meant wasted memory
in cases where it wasn't used. It also meant a bit of confusion as the
queue might be accidently used in places where it shouldn't be.
Remove the mpsc queue member from struct rtio_iodev and the last remaining
usages of it. Will ensure RTIO for 3.7 LTS avoids causing unneeded churn
for future users.
Signed-off-by: Tom Burdick <thomas.burdick@intel.com>
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