[PATCH 2.6.12-rc1] API for true Random Number Generators to add entropy

[David McCullough <davidm@snapgear.com>]

Hi all,

Here is a revised patch for 2.6.12-rc1 that adds a routine:

    add_true_randomness(__u32 *buf, int nwords);

so that true random number generator device drivers can add a entropy
to the system.

Cheers,
Davidm

Signed-off-by: David McCullough <davidm@snapgear.com>

--- linux-2.6.12-rc1.orig/drivers/char/random.c	2005-03-18 11:33:49.000000000 +1000
+++ linux-2.6.12-rc1/drivers/char/random.c	2005-03-24 16:16:40.000000000 +1000
@@ -1148,6 +1148,36 @@
 EXPORT_SYMBOL(generate_random_uuid);
 
 /********************************************************************
+ * provide a mechanism for HW to add entropy that is of
+ * very good quality from a true random number generator
+ ***************************************************************/
+
+void add_true_randomness(__u32 *buf, int nwords)
+{
+	struct entropy_store *r;
+	int wakeup_check = 0;
+
+	/*
+	 * if we have too much entropy, put some in the secondary pool
+	 */
+	r = &blocking_pool;
+	if (r->entropy_count >= r->poolinfo->POOLBITS)
+		r = &nonblocking_pool;
+	else
+		wakeup_check = (r->entropy_count < random_read_wakeup_thresh);
+
+	add_entropy_words(r, buf, nwords);
+	credit_entropy_store(r, nwords * 32);
+
+	/*
+	 * wakeup if we added enough entropy to cross the threshold
+	 */
+	if (wakeup_check && r->entropy_count >= random_read_wakeup_thresh)
+		wake_up_interruptible(&random_read_wait);
+}
+EXPORT_SYMBOL(add_true_randomness);
+
+/********************************************************************
  *
  * Sysctl interface
  *
--- linux-2.6.12-rc1.orig/include/linux/random.h	2005-03-18 11:34:37.000000000 +1000
+++ linux-2.6.12-rc1/include/linux/random.h	2005-03-24 15:59:42.000000000 +1000
@@ -48,6 +48,8 @@
 				 unsigned int value);
 extern void add_interrupt_randomness(int irq);
 
+extern void add_true_randomness(__u32 *buf, int nwords);
+
 extern void get_random_bytes(void *buf, int nbytes);
 void generate_random_uuid(unsigned char uuid_out[16]);
 

-- 
David McCullough, davidm@snapgear.com  Ph:+61 7 34352815 http://www.SnapGear.com
Custom Embedded Solutions + Security   Fx:+61 7 38913630 http://www.uCdot.org