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RANDOM_HARVEST(9)      FreeBSD Kernel Developer's Manual     RANDOM_HARVEST(9)

NAME
     random_harvest -- gather entropy from the kernel for the entropy device

SYNOPSIS
     #include <sys/types.h>
     #include <sys/random.h>

     void
     random_harvest_direct(void	*entropy, u_int	size, enum esource source);

     void
     random_harvest_fast(void *entropy,	u_int size, enum esource source);

     void
     random_harvest_queue(void *entropy, u_int size, enum esource source);

DESCRIPTION
     The random_harvest_*() functions are used by device drivers and other
     kernel processes to pass data that	is considered (at least	partially)
     stochastic	to the entropy device.

     The caller	should pass a pointer pointing to the ``random'' data in
     entropy.  The argument size contains the number of	bytes pointed to.  The
     source is chosen from one of the values enumerated	in sys/dev/random.h.
     and is used to indicate the source	of the entropy.

     The random_harvest_direct() variant is used for early harvesting before
     any multitasking is enabled.

     The random_harvest_fast() variant is used by sources that should not take
     a performance hit from harvesting,	as they	are high-rate sources.	Some
     entropy is	sacrificed, but	the high rate of supply	will compensate	for
     this.

     The random_harvest_queue()	variant	is used	for general harvesting and is
     the default choice	for most entropy sources such as interrupts or console
     events.

     Interrupt harvesting has been in part simplified for the kernel program-
     mer.  If a	device driver registers	an interrupt handler with
     BUS_SETUP_INTR(9) or bus_setup_intr(9), then it is	only necessary to
     include the INTR_ENTROPY bit in the flags argument	to have	that interrupt
     source be used for	entropy	harvesting.  This should be done wherever
     practicable.

SEE ALSO
     random(4),	BUS_SETUP_INTR(9)

AUTHORS
     The FreeBSD random(4) entropy device and supporting documentation was
     written by	Mark R V Murray.

FreeBSD	Ports 11.2		August 26, 2018		    FreeBSD Ports 11.2

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHORS

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