x86: put timer_rand_state pointer into irq_desc

irq_timer_state[] is a NR_IRQS sized array that is a side-by array to
the real irq_desc[] array.

Integrate that field into the (now dynamic) irq_desc dynamic array and
save some RAM.

v2: keep the old way to support arch not support irq_desc

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

drivers/char/random.c

@@ -558,7 +558,7 @@ struct timer_rand_state {
 	unsigned dont_count_entropy:1;
 };
 
-static struct timer_rand_state input_timer_state;
+#ifndef CONFIG_HAVE_SPARSE_IRQ
 
 #ifdef CONFIG_HAVE_DYN_ARRAY
 static struct timer_rand_state **irq_timer_state;
@@ -567,6 +567,51 @@ DEFINE_DYN_ARRAY(irq_timer_state, sizeof(struct timer_rand_state *), nr_irqs, PA
 static struct timer_rand_state *irq_timer_state[NR_IRQS];
 #endif
 
+static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
+{
+	if (irq >= nr_irqs)
+		return NULL;
+
+	return irq_timer_state[irq];
+}
+
+static void set_timer_rand_state(unsigned int irq, struct timer_rand_state *state)
+{
+	if (irq >= nr_irqs)
+		return;
+
+	irq_timer_state[irq] = state;
+}
+
+#else
+
+static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
+{
+	struct irq_desc *desc;
+
+	desc = irq_to_desc(irq);
+
+	if (!desc)
+		return NULL;
+
+	return desc->timer_rand_state;
+}
+
+static void set_timer_rand_state(unsigned int irq, struct timer_rand_state *state)
+{
+	struct irq_desc *desc;
+
+	desc = irq_to_desc(irq);
+
+	if (!desc)
+		return;
+
+	desc->timer_rand_state = state;
+}
+#endif
+
+static struct timer_rand_state input_timer_state;
+
 /*
  * This function adds entropy to the entropy "pool" by using timing
  * delays.  It uses the timer_rand_state structure to make an estimate
@@ -654,11 +699,15 @@ EXPORT_SYMBOL_GPL(add_input_randomness);
 
 void add_interrupt_randomness(int irq)
 {
-	if (irq >= nr_irqs || irq_timer_state[irq] == NULL)
+	struct timer_rand_state *state;
+
+	state = get_timer_rand_state(irq);
+
+	if (state == NULL)
 		return;
 
 	DEBUG_ENT("irq event %d\n", irq);
-	add_timer_randomness(irq_timer_state[irq], 0x100 + irq);
+	add_timer_randomness(state, 0x100 + irq);
 }
 
 #ifdef CONFIG_BLOCK
@@ -918,7 +967,14 @@ void rand_initialize_irq(int irq)
 {
 	struct timer_rand_state *state;
 
-	if (irq >= nr_irqs || irq_timer_state[irq])
+#ifndef CONFIG_HAVE_SPARSE_IRQ
+	if (irq >= nr_irqs)
+		return;
+#endif
+
+	state = get_timer_rand_state(irq);
+
+	if (state)
 		return;
 
 	/*
@@ -927,7 +983,7 @@ void rand_initialize_irq(int irq)
 	 */
 	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
 	if (state)
-		irq_timer_state[irq] = state;
+		set_timer_rand_state(irq, state);
 }
 
 #ifdef CONFIG_BLOCK

include/linux/irq.h

@@ -127,6 +127,7 @@ struct irq_chip {
 	const char	*typename;
 };
 
+struct timer_rand_state;
 /**
  * struct irq_desc - interrupt descriptor
  *
@@ -155,6 +156,7 @@ struct irq_desc {
 	unsigned int		irq;
 #ifdef CONFIG_HAVE_SPARSE_IRQ
 	struct irq_desc		*next;
+	struct timer_rand_state *timer_rand_state;
 #endif
 	irq_flow_handler_t	handle_irq;
 	struct irq_chip		*chip;