Registers a trace that is accessed by a set/get pair of functions.
LIBRARY
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DESCRIPTION
A call to register_ftrace(nm, (g,s), m) registers an integer-valued
trace variable that is updated with the s function and whose value
is read with the g function. The variable is given the name nm
and the variable’s maximum allowed value is m. The trace’s default
is the value of g(), which is called just once as part of the
registration procedure.
FAILURE
Fails if the given name is already in use as a trace variable, or if
the maximum or the default value (returned by g()) is less than
zero.
COMMENTS
The two functions provide a more general way of accessing something
that may not be actually be an integer reference, even though this is
the interface that the various trace functions present.