---

yaml
---
r: 320715
b: refs/heads/master
c: a2080a6
h: refs/heads/master
i:
  320713: c61d937
  320711: 1cd7719
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 902c098a3663de3fa18639efbb71b6080f0bcd3c
+refs/heads/master: a2080a67abe9e314f9e9c2cc3a4a176e8a8f8793

trunk/drivers/char/random.c

@@ -125,11 +125,20 @@
  * The current exported interfaces for gathering environmental noise
  * from the devices are:
  *
+ *	void add_device_randomness(const void *buf, unsigned int size);
  * 	void add_input_randomness(unsigned int type, unsigned int code,
  *                                unsigned int value);
  *	void add_interrupt_randomness(int irq, int irq_flags);
  * 	void add_disk_randomness(struct gendisk *disk);
  *
+ * add_device_randomness() is 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).
+ *
  * add_input_randomness() uses the input layer interrupt timing, as well as
  * the event type information from the hardware.
  *
@@ -646,6 +655,25 @@ static void set_timer_rand_state(unsigned int irq,
 }
 #endif
 
+/*
+ * Add device- or boot-specific data to the input and nonblocking
+ * pools to help initialize them to unique values.
+ *
+ * None of this adds any entropy, it is meant to avoid the
+ * problem of the nonblocking pool having similar initial state
+ * across largely identical devices.
+ */
+void add_device_randomness(const void *buf, unsigned int size)
+{
+	unsigned long time = get_cycles() ^ jiffies;
+
+	mix_pool_bytes(&input_pool, buf, size, NULL);
+	mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
+	mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
+	mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
+}
+EXPORT_SYMBOL(add_device_randomness);
+
 static struct timer_rand_state input_timer_state;
 
 /*

trunk/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);