Subject: new MI/MD interface for rnd(4)
To: None <,>
From: Bill Sommerfeld <>
List: tech-kern
Date: 06/05/2000 19:55:41
I just committed changes to the i386 port and to the /dev/random
driver (sys/dev/rnd.c) to let it use a higher-resolution cycle counter
in the timestamps it uses for randomness collection.

Here's a slight rephrasing of the commit message:

If __HAVE_CPU_TIMESTAMP is defined (currently in <machine/types.h>,
which is a dumping ground for similar options), <machine/rnd.h> exists
and defines two functions:
  1)    u_int32_t cpu_timestamp(void);
returns the 32 low order bits of a reasonably high frequency counter.
  2)    int cpu_havetimestamp(void);
returns non-zero if cpu_timestamp() actually works.

The timestamp counter should run at a frequency greater than 1 MHz
(otherwise, microtime would be sufficient); other than that, the exact
frequency and origin of the counter are unspecified.

Let me know you have any comments/questions on this (extremely
trivial) optional additional interface.  I suspect that other ports
should be able to use this interface pretty easily.

					- Bill