Oddly, drivers/input/input.c seems to reference a symbol which is apparently in another module but not exported.
Index: linux-2.6.15gum/drivers/char/random.c
===================================================================
--- linux-2.6.15gum.orig/drivers/char/random.c
+++ linux-2.6.15gum/drivers/char/random.c
@@ -646,6 +646,7 @@ extern void add_input_randomness(unsigne
 	add_timer_randomness(&input_timer_state,
 			     (type << 4) ^ code ^ (code >> 4) ^ value);
 }
+EXPORT_SYMBOL(add_input_randomness);
 
 void add_interrupt_randomness(int irq)
 {