Since core ABI 21, users can decide whether a new element should be
made public or private depending on the value of clone flags added to
the new long form of all element creation calls, i.e. evl_create_*().
All evl_new_*() calls become a shorthand for their respective long
form with reasonable default arguments, including private visibility.
As a shorthand, libevl also interprets a slash character leading the
name argument passed to these services as an implicit request for
creating a public element. In other words, this is the same as passing
EVL_CLONE_PUBLIC in the clone flags.
A public element appears as a cdev in the /dev/evl hierarchy, which
means that it is visible to other processes, which may share it. On
the contrary, a private element is only known from the process
creating it, although it does appear in the /sysfs hierarchy
regardless.
e.g.:
efd = evl_attach_self("/visible-thread");
total 0
crw-rw---- 1 root root 248, 1 Apr 17 11:59 clone
crw-rw---- 1 root root 246, 0 Apr 17 11:59 visible-thread
or,
efd = evl_attach_self("private-thread");
total 0
crw-rw---- 1 root root 248, 1 Apr 17 11:59 clone
Signed-off-by: Philippe Gerum <rpm@xenomai.org>
Zero-initialized semaphores timed on the monotonic clock is the
most common form used by applications. Allow people to write more
compact code by providing creation calls and static initializers aimed
at building these directly:
- evl_new_sem(), EVL_SEM_INITIALIZER() for zero-init semaphores
timed on the monotonic clock.
- evl_new_sem_any() and EVL_SEM_ANY_INITIALIZER() usable for any
initialization form, specifying the clock and init value.
The EVL shim library mimics the behavior of the original EVL API based
on plain POSIX calls from the native *libc, which does not require the
EVL core to be enabled in the host kernel. It is useful when the
real-time guarantees delivered by the EVL core are not required for
quick prototyping or debugging application code.
Philippe Gerum