UNREGISTER_CHRDEV_RE(9) Char devices UNREGISTER_CHRDEV_RE(9)NAME
unregister_chrdev_region - return a range of device numbers
SYNOPSIS
void unregister_chrdev_region(dev_t from, unsigned count);
ARGUMENTS
from
the first in the range of numbers to unregister
count
the number of device numbers to unregister
DESCRIPTION
This function will unregister a range of count device numbers, starting with from. The caller should normally be the one who allocated
those numbers in the first place...
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 UNREGISTER_CHRDEV_RE(9)
Check Out this Related Man Page
RANDOM(9) BSD Kernel Developer's Manual RANDOM(9)NAME
arc4rand, arc4random, random, read_random, srandom -- supply pseudo-random numbers
SYNOPSIS
#include <sys/libkern.h>
void
srandom(u_long seed);
u_long
random(void);
void
arc4rand(void *ptr, u_int length, int reseed);
uint32_t
arc4random(void);
#include <sys/random.h>
int
read_random(void *buffer, int count);
DESCRIPTION
The random() function will by default produce a sequence of numbers that can be duplicated by calling srandom() with '1' as the seed. The
srandom() function may be called with any arbitrary seed value to get slightly more unpredictable numbers. It is important to remember that
the random() function is entirely predictable, and is therefore not of use where knowledge of the sequence of numbers may be of benefit to an
attacker.
The arc4rand() function will return very good quality random numbers, slightly better suited for security-related purposes. The random num-
bers from arc4rand() are seeded from the entropy device if it is available. Automatic reseeds happen after a certain timeinterval and after
a certain number of bytes have been delivered. A forced reseed can be forced by passing a non-zero value in the reseed argument.
The read_random() function is used to return entropy directly from the entropy device if it has been loaded. If the entropy device is not
loaded, then the buffer is filled with output generated by random(). The buffer is filled with no more than count bytes. It is advised that
read_random() is not used; instead use arc4rand()
All the bits generated by random(), arc4rand() and read_random() are usable. For example, 'random()&01' will produce a random binary value.
The arc4random() is a convenience function which calls arc4rand() to return a 32 bit pseudo-random integer.
RETURN VALUES
The random() function uses a non-linear additive feedback random number generator employing a default table of size 31 long integers to
return successive pseudo-random numbers in the range from 0 to (2**31)-1. The period of this random number generator is very large, approxi-
mately 16*((2**31)-1).
The arc4rand() function uses the RC4 algorithm to generate successive pseudo-random bytes. The arc4random() function uses arc4rand() to gen-
erate pseudo-random numbers in the range from 0 to (2**32)-1.
The read_random() function returns the number of bytes placed in buffer.
AUTHORS
Dan Moschuk wrote arc4random().
Mark R V Murray wrote read_random().
BSD September 25, 2000 BSD