random: create add_device_randomness() interface

Add a new interface, add_device_randomness() for adding data to the
random pool that is likely to differ between two devices (or possibly
even per boot).  This would be things like MAC addresses or serial
numbers, or the read-out of the RTC. This does *not* add any actual
entropy to the pool, but it initializes the pool to different values
for devices that might otherwise be identical and have very little
entropy available to them (particularly common in the embedded world).

[ Modified by tytso to mix in a timestamp, since there may be some
  variability caused by the time needed to detect/configure the hardware
  in question. ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/random.h b/include/linux/random.h
index 6ef39d7f2db1..e14b4387354a 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -50,6 +50,7 @@ struct rnd_state {
 
 extern void rand_initialize_irq(int irq);
 
+extern void add_device_randomness(const void *, unsigned int);
 extern void add_input_randomness(unsigned int type, unsigned int code,
                                  unsigned int value);
 extern void add_interrupt_randomness(int irq, int irq_flags);