Jorge Ramirez-Ortiz authored Mar 28, 2019 and Philippe Gerum committed Jun 05, 2021

Elements:
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Basic features that cant be implemented from userland sharable between
processes.

Threads, monitors, xbufs and clocks -> every instance is backed by a
device in /dev/evl which allows sharing.

Utilities
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poll is a private-process construct; all poll groups are obtained from a
single multiplex device: /dev/evl/poll. They cannot be shared.

timers are in essence timerfd directly obtained from clocks, they don't
exist on their own, and are process-local too.

proxies are backed by a device in /dev/evl to allow for sharing, but
this is not something essential.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>