Vector sharing (Large I/O system support)

diff -Naurp linux-2.6.8-rc1/arch/ia64/kernel/iosapic.c linux-2.6.8-rc1-changed/arch/ia64/kernel/iosapic.c
@@ -103,15 +103,23 @@ static spinlock_t iosapic_lock = SPIN_LO
 
 /* These tables map IA-64 vectors to the IOSAPIC pin that generates this vector. */
 
-static struct iosapic_intr_info {
+struct iosapic_pin {
+	struct list_head pin_list;	/* IOSAPIC pins which share the same vector */
 	char		*addr;		/* base address of IOSAPIC */
-	u32		low32;		/* current value of low word of Redirection table entry */
 	unsigned int	gsi_base;	/* first GSI assigned to this IOSAPIC */
-	char		rte_index;	/* IOSAPIC RTE index (-1 => not an IOSAPIC interrupt) */
+	char		rte_index;	/* IOSAPIC RTE index */
+};
+
+static struct iosapic_intr_info {
+	struct list_head pin_head;	/* List head of IOSAPIC pins */
+	struct iosapic_pin pin;		/* First entry of IOSAPIC pins list */
+	int		count;		/* # of pins (0 => not an IOSAPIC interrupt) */
+	u32		low32;		/* current value of low word of Redirection table entry */
 	unsigned char	dmode	: 3;	/* delivery mode (see iosapic.h) */
 	unsigned char 	polarity: 1;	/* interrupt polarity (see iosapic.h) */
 	unsigned char	trigger	: 1;	/* trigger mode (see iosapic.h) */
-} iosapic_intr_info[IA64_NUM_VECTORS];
+	unsigned char	type	: 1;	/* Vector type */
+} iosapic_intr_info[IA64_NUM_VECTORS] __cacheline_aligned;
 
 static struct iosapic {
 	char		*addr;		/* base address of IOSAPIC */

@@ -144,10 +152,14 @@ static inline int
 _gsi_to_vector (unsigned int gsi)
 {
 	struct iosapic_intr_info *info;
+	struct iosapic_pin *pin;
 
-	for (info = iosapic_intr_info; info < iosapic_intr_info + IA64_NUM_VECTORS; ++info)
-		if (info->gsi_base + info->rte_index = gsi)
-			return info - iosapic_intr_info;
+	for (info = iosapic_intr_info; info < iosapic_intr_info + IA64_NUM_VECTORS; ++info) {
+		list_for_each_entry(pin, &info->pin_head, pin_list) {
+			if (pin->gsi_base + pin->rte_index = gsi)
+				return info - iosapic_intr_info;
+		}
+	}
 	return -1;
 }
 

@@ -171,22 +183,33 @@ gsi_to_irq (unsigned int gsi)
 	return _gsi_to_vector(gsi);
 }
 
+static inline struct iosapic_pin *
+gsi_vector_to_pin (unsigned int gsi, unsigned int vector)
+{
+	struct iosapic_pin *pin;
+
+	list_for_each_entry(pin, &iosapic_intr_info[vector].pin_head, pin_list) {
+		if (pin->gsi_base + pin->rte_index = gsi)
+			return pin;
+	}
+	return NULL;
+}
+
 static void
-set_rte (unsigned int vector, unsigned int dest, int mask)
+set_rte (unsigned int gsi, unsigned int vector, unsigned int dest, int mask)
 {
 	unsigned long pol, trigger, dmode, flags;
 	u32 low32, high32;
 	char *addr;
 	int rte_index;
 	char redir;
+	struct iosapic_pin *pin;
 
 	DBG(KERN_DEBUG"IOSAPIC: routing vector %d to 0x%x\n", vector, dest);
 
-	rte_index = iosapic_intr_info[vector].rte_index;
-	if (rte_index < 0)
+	if (!iosapic_intr_info[vector].count)
 		return;		/* not an IOSAPIC interrupt */
 
-	addr    = iosapic_intr_info[vector].addr;
 	pol     = iosapic_intr_info[vector].polarity;
 	trigger = iosapic_intr_info[vector].trigger;
 	dmode   = iosapic_intr_info[vector].dmode;

@@ -217,6 +240,17 @@ set_rte (unsigned int vector, unsigned i
 
 	spin_lock_irqsave(&iosapic_lock, flags);
 	{
+		if (!(iosapic_intr_info[vector].low32 & IOSAPIC_MASK))
+			low32 &= ~IOSAPIC_MASK;
+
+		pin = gsi_vector_to_pin(gsi, vector);
+		if (!pin) {
+			spin_unlock_irqrestore(&iosapic_lock, flags);
+			return;
+		}
+		rte_index = pin->rte_index;
+		addr    = pin->addr;
+
 		iosapic_write(addr, IOSAPIC_RTE_HIGH(rte_index), high32);
 		iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
 		iosapic_intr_info[vector].low32 = low32;

@@ -238,18 +272,20 @@ mask_irq (unsigned int irq)
 	u32 low32;
 	int rte_index;
 	ia64_vector vec = irq_to_vector(irq);
-
-	addr = iosapic_intr_info[vec].addr;
-	rte_index = iosapic_intr_info[vec].rte_index;
-
-	if (rte_index < 0)
+	struct iosapic_pin *pin;
+  
+	if (!iosapic_intr_info[vec].count)
 		return;			/* not an IOSAPIC interrupt! */
 
 	spin_lock_irqsave(&iosapic_lock, flags);
 	{
 		/* set only the mask bit */
 		low32 = iosapic_intr_info[vec].low32 |= IOSAPIC_MASK;
-		iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		list_for_each_entry(pin, &iosapic_intr_info[vec].pin_head, pin_list) {
+			addr = pin->addr;
+			rte_index = pin->rte_index;
+			iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		}
 	}
 	spin_unlock_irqrestore(&iosapic_lock, flags);
 }

@@ -262,16 +298,19 @@ unmask_irq (unsigned int irq)
 	u32 low32;
 	int rte_index;
 	ia64_vector vec = irq_to_vector(irq);
+	struct iosapic_pin *pin;
 
-	addr = iosapic_intr_info[vec].addr;
-	rte_index = iosapic_intr_info[vec].rte_index;
-	if (rte_index < 0)
+	if (!iosapic_intr_info[vec].count)
 		return;			/* not an IOSAPIC interrupt! */
 
 	spin_lock_irqsave(&iosapic_lock, flags);
 	{
 		low32 = iosapic_intr_info[vec].low32 &= ~IOSAPIC_MASK;
-		iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		list_for_each_entry(pin, &iosapic_intr_info[vec].pin_head, pin_list) {
+			addr = pin->addr;
+			rte_index = pin->rte_index;
+			iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		}
 	}
 	spin_unlock_irqrestore(&iosapic_lock, flags);
 }

@@ -287,6 +326,7 @@ iosapic_set_affinity (unsigned int irq, 
 	char *addr;
 	int redir = (irq & IA64_IRQ_REDIRECTED) ? 1 : 0;
 	ia64_vector vec;
+	struct iosapic_pin *pin;
 
 	irq &= (~IA64_IRQ_REDIRECTED);
 	vec = irq_to_vector(irq);

@@ -296,10 +336,7 @@ iosapic_set_affinity (unsigned int irq, 
 
 	dest = cpu_physical_id(first_cpu(mask));
 
-	rte_index = iosapic_intr_info[vec].rte_index;
-	addr = iosapic_intr_info[vec].addr;
-
-	if (rte_index < 0)
+	if (!iosapic_intr_info[vec].count)
 		return;			/* not an IOSAPIC interrupt */
 
 	set_irq_affinity_info(irq, dest, redir);

@@ -312,15 +349,19 @@ iosapic_set_affinity (unsigned int irq, 
 		low32 = iosapic_intr_info[vec].low32 & ~(7 << IOSAPIC_DELIVERY_SHIFT);
 
 		if (redir)
-		        /* change delivery mode to lowest priority */
+			/* change delivery mode to lowest priority */
 			low32 |= (IOSAPIC_LOWEST_PRIORITY << IOSAPIC_DELIVERY_SHIFT);
 		else
-		        /* change delivery mode to fixed */
+			/* change delivery mode to fixed */
 			low32 |= (IOSAPIC_FIXED << IOSAPIC_DELIVERY_SHIFT);
 
 		iosapic_intr_info[vec].low32 = low32;
-		iosapic_write(addr, IOSAPIC_RTE_HIGH(rte_index), high32);
-		iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		list_for_each_entry(pin, &iosapic_intr_info[vec].pin_head, pin_list) {
+			rte_index = pin->rte_index;
+			addr = pin->addr;
+			iosapic_write(addr, IOSAPIC_RTE_HIGH(rte_index), high32);
+			iosapic_write(addr, IOSAPIC_RTE_LOW(rte_index), low32);
+		}
 	}
 	spin_unlock_irqrestore(&iosapic_lock, flags);
 #endif

@@ -341,9 +382,11 @@ static void
 iosapic_end_level_irq (unsigned int irq)
 {
 	ia64_vector vec = irq_to_vector(irq);
+	struct iosapic_pin *pin;
 
 	move_irq(irq);
-	iosapic_eoi(iosapic_intr_info[vec].addr, vec);
+	list_for_each_entry(pin, &iosapic_intr_info[vec].pin_head, pin_list)
+		iosapic_eoi(pin->addr, vec);
 }
 
 #define iosapic_shutdown_level_irq	mask_irq

@@ -424,6 +467,30 @@ iosapic_version (char *addr)
 }
 
 /*
+ * Find a sharable vector.
+ */
+static int
+iosapic_find_sharable_vector (unsigned long trigger, unsigned long polarity)
+{
+	int i;
+	static int next_vector = IA64_FIRST_DEVICE_VECTOR;
+
+	for (i = 0; i < IA64_NUM_DEVICE_VECTORS; i++) {
+		if (next_vector > IA64_LAST_DEVICE_VECTOR)
+			next_vector = IA64_FIRST_DEVICE_VECTOR;
+
+		if (iosapic_intr_info[next_vector].type = IOSAPIC_VECTOR_SHARABLE &&
+		    iosapic_intr_info[next_vector].trigger = trigger &&
+		    iosapic_intr_info[next_vector].polarity = polarity)
+			return next_vector++;
+
+		next_vector++;
+	}
+
+	return -1;
+}
+
+/*
  * if the given vector is already owned by other,
  *  assign a new vector for the other and make the vector available
  */

@@ -432,22 +499,22 @@ iosapic_reassign_vector (int vector)
 {
 	int new_vector;
 
-	if (iosapic_intr_info[vector].rte_index >= 0 || iosapic_intr_info[vector].addr
-	    || iosapic_intr_info[vector].gsi_base || iosapic_intr_info[vector].dmode
-	    || iosapic_intr_info[vector].polarity || iosapic_intr_info[vector].trigger)
-	{
+	if (iosapic_intr_info[vector].count > 0) {
 		new_vector = assign_irq_vector(AUTO_ASSIGN);
 		printk(KERN_INFO "Reassigning vector %d to %d\n", vector, new_vector);
 		memcpy(&iosapic_intr_info[new_vector], &iosapic_intr_info[vector],
 		       sizeof(struct iosapic_intr_info));
+		INIT_LIST_HEAD(&iosapic_intr_info[new_vector].pin_head);
+		list_add(&iosapic_intr_info[new_vector].pin.pin_list,
+			 &iosapic_intr_info[new_vector].pin_head);
 		memset(&iosapic_intr_info[vector], 0, sizeof(struct iosapic_intr_info));
-		iosapic_intr_info[vector].rte_index = -1;
+		INIT_LIST_HEAD(&iosapic_intr_info[vector].pin_head);
 	}
 }
 
 static void
 register_intr (unsigned int gsi, int vector, unsigned char delivery,
-	       unsigned long polarity, unsigned long trigger)
+	       unsigned long polarity, unsigned long trigger, unsigned long type)
 {
 	irq_desc_t *idesc;
 	struct hw_interrupt_type *irq_type;

@@ -455,6 +522,7 @@ register_intr (unsigned int gsi, int vec
 	int index;
 	unsigned long gsi_base;
 	char *iosapic_address;
+	struct iosapic_pin *pin;
 
 	index = find_iosapic(gsi);
 	if (index < 0) {

@@ -465,13 +533,39 @@ register_intr (unsigned int gsi, int vec
 	iosapic_address = iosapic_lists[index].addr;
 	gsi_base = iosapic_lists[index].gsi_base;
 
+	pin = gsi_vector_to_pin(gsi, vector);
+	if (!pin) {	/* Register a new interrupt */
+		if (!iosapic_intr_info[vector].count) {
+			pin = &iosapic_intr_info[vector].pin;
+			iosapic_intr_info[vector].low32 = IOSAPIC_MASK;
+		}
+		else if ((pin = kmalloc(sizeof(struct iosapic_pin), GFP_KERNEL)) = NULL) {
+			printk (KERN_WARNING "%s: cannot allocate memory\n", __FUNCTION__);
+			return;
+		}
+		list_add_tail(&pin->pin_list, &iosapic_intr_info[vector].pin_head);
+		iosapic_intr_info[vector].count++;
+	} else {	/* Override an existing interrupt */
+		if (iosapic_intr_info[vector].count > 1) {
+			if (iosapic_intr_info[vector].trigger != trigger ||
+			    iosapic_intr_info[vector].polarity != polarity ||
+			    type = IOSAPIC_VECTOR_EXCLUSIVE)
+			{
+				printk(KERN_WARNING "%s: cannot override an interrupt\n",
+				       __FUNCTION__);
+				return;
+			}
+		}
+	}
+
 	rte_index = gsi - gsi_base;
-	iosapic_intr_info[vector].rte_index = rte_index;
+	pin->rte_index = rte_index;
+	pin->addr     = iosapic_address;
+	pin->gsi_base = gsi_base;
 	iosapic_intr_info[vector].polarity = polarity;
 	iosapic_intr_info[vector].dmode    = delivery;
-	iosapic_intr_info[vector].addr     = iosapic_address;
-	iosapic_intr_info[vector].gsi_base = gsi_base;
 	iosapic_intr_info[vector].trigger  = trigger;
+	iosapic_intr_info[vector].type     = type;
 
 	if (trigger = IOSAPIC_EDGE)
 		irq_type = &irq_type_iosapic_edge;

@@ -488,10 +582,23 @@ register_intr (unsigned int gsi, int vec
 }
 
 static unsigned int
-get_target_cpu (void)
+get_target_cpu (int vector)
 {
 #ifdef CONFIG_SMP
 	static int cpu = -1;
+	int irq;
+	cpumask_t cpumask, cpumask_all = CPU_MASK_ALL;
+
+	/*
+	 * if this vector already has its destination CPU, use the
+	 * same destination CPU.
+	 */
+	for (irq = 0; irq < NR_IRQS; ++irq)
+		if (irq_to_vector(irq) = vector) {
+			cpumask = get_irq_affinity_info(irq);
+			if (!cpus_equal(cpumask, cpumask_all))
+				return cpu_physical_id(first_cpu(cpumask));
+		}
 
 	/*
 	 * If the platform supports redirection via XTP, let it

@@ -549,19 +656,40 @@ iosapic_register_intr (unsigned int gsi,
 			return vector;
 		}
 
-		vector = assign_irq_vector(AUTO_ASSIGN);
-		dest = get_target_cpu();
-		register_intr(gsi, vector, IOSAPIC_LOWEST_PRIORITY,
-			polarity, trigger);
+		vector = assign_irq_vector_nopanic(AUTO_ASSIGN);
+		if (vector < 0)
+			vector = iosapic_find_sharable_vector(trigger, polarity);
+		if (vector < 0)
+			panic("%s: out of interrupt vectors!\n", __FUNCTION__);
 	}
 	spin_unlock_irqrestore(&iosapic_lock, flags);
 
+	spin_lock_irqsave(&irq_descp(vector)->lock, flags);
+	spin_lock(&iosapic_lock);
+	{
+		int tmp_vector = gsi_to_vector(gsi);
+		if (tmp_vector > 0) {
+			if (!iosapic_intr_info[vector].count)
+				free_irq_vector(vector);
+			spin_unlock(&iosapic_lock);
+			spin_unlock_irqrestore(&irq_descp(vector)->lock, flags);
+			return tmp_vector;
+		}
+		dest = get_target_cpu(vector);
+		register_intr(gsi, vector, IOSAPIC_LOWEST_PRIORITY,
+			polarity, trigger, trigger = IOSAPIC_EDGE ?
+			IOSAPIC_VECTOR_EXCLUSIVE : IOSAPIC_VECTOR_SHARABLE);
+	}
+	spin_unlock(&iosapic_lock);
+
 	printk(KERN_INFO "GSI %u (%s, %s) -> CPU %d (0x%04x) vector %d\n",
 	       gsi, (trigger = IOSAPIC_EDGE ? "edge" : "level"),
 	       (polarity = IOSAPIC_POL_HIGH ? "high" : "low"),
 	       cpu_logical_id(dest), dest, vector);
 
-	set_rte(vector, dest, 1);
+	set_rte(gsi, vector, dest, 1);
+
+	spin_unlock_irqrestore(&irq_descp(vector)->lock, flags);
 	return vector;
 }
 

@@ -603,7 +731,7 @@ iosapic_register_platform_intr (u32 int_
 		return -1;
 	}
 
-	register_intr(gsi, vector, delivery, polarity, trigger);
+	register_intr(gsi, vector, delivery, polarity, trigger, IOSAPIC_VECTOR_EXCLUSIVE);
 
 	printk(KERN_INFO "PLATFORM int %s (0x%x): GSI %u (%s, %s) -> CPU %d (0x%04x) vector %d\n",
 	       int_type < ARRAY_SIZE(name) ? name[int_type] : "unknown",

@@ -611,7 +739,7 @@ iosapic_register_platform_intr (u32 int_
 	       (polarity = IOSAPIC_POL_HIGH ? "high" : "low"),
 	       cpu_logical_id(dest), dest, vector);
 
-	set_rte(vector, dest, mask);
+	set_rte(gsi, vector, dest, mask);
 	return vector;
 }
 

@@ -630,14 +758,14 @@ iosapic_override_isa_irq (unsigned int i
 
 	vector = isa_irq_to_vector(isa_irq);
 
-	register_intr(gsi, vector, IOSAPIC_LOWEST_PRIORITY, polarity, trigger);
+	register_intr(gsi, vector, IOSAPIC_LOWEST_PRIORITY, polarity, trigger, IOSAPIC_VECTOR_EXCLUSIVE);
 
 	DBG("ISA: IRQ %u -> GSI %u (%s,%s) -> CPU %d (0x%04x) vector %d\n",
 	    isa_irq, gsi, trigger = IOSAPIC_EDGE ? "edge" : "level",
 	    polarity = IOSAPIC_POL_HIGH ? "high" : "low",
 	    cpu_logical_id(dest), dest, vector);
 
-	set_rte(vector, dest, 1);
+	set_rte(gsi, vector, dest, 1);
 }
 
 void __init

@@ -645,8 +773,10 @@ iosapic_system_init (int system_pcat_com
 {
 	int vector;
 
-	for (vector = 0; vector < IA64_NUM_VECTORS; ++vector)
-		iosapic_intr_info[vector].rte_index = -1;	/* mark as unused */
+	for (vector = 0; vector < IA64_NUM_VECTORS; ++vector) {
+		iosapic_intr_info[vector].count = 0;	/* mark as unused */
+		INIT_LIST_HEAD(&iosapic_intr_info[vector].pin_head);
+	}
 
 	pcat_compat = system_pcat_compat;
 	if (pcat_compat) {

diff -Naurp linux-2.6.8-rc1/arch/ia64/kernel/irq.c linux-2.6.8-rc1-changed/arch/ia64/kernel/irq.c
@@ -949,6 +949,11 @@ void set_irq_affinity_info (unsigned int
 	}
 }
 
+cpumask_t get_irq_affinity_info (unsigned int irq)
+{
+	return irq_affinity[irq];
+}
+
 static int irq_affinity_read_proc (char *page, char **start, off_t off,
 			int count, int *eof, void *data)
 {

diff -Naurp linux-2.6.8-rc1/arch/ia64/kernel/irq_ia64.c linux-2.6.8-rc1-changed/arch/ia64/kernel/irq_ia64.c
@@ -74,15 +74,44 @@ irq_exit (void)
 	preempt_enable_no_resched();
 }
 
+static unsigned long ia64_vector_mask[BITS_TO_LONGS(IA64_NUM_DEVICE_VECTORS)];
+
+int
+assign_irq_vector_nopanic (int irq)
+{
+	int pos, vector;
+ again:
+	pos = find_first_zero_bit(ia64_vector_mask, IA64_NUM_DEVICE_VECTORS);
+	vector = IA64_FIRST_DEVICE_VECTOR + pos;
+	if (vector > IA64_LAST_DEVICE_VECTOR)
+		return -1;
+	if (test_and_set_bit(pos, ia64_vector_mask))
+		goto again;
+	return vector;
+}
+
 int
 assign_irq_vector (int irq)
 {
-	static int next_vector = IA64_FIRST_DEVICE_VECTOR;
+	int vector = assign_irq_vector_nopanic(irq);
 
-	if (next_vector > IA64_LAST_DEVICE_VECTOR)
-		/* XXX could look for sharable vectors instead of panic'ing... */
+	if (vector = -1)
 		panic("assign_irq_vector: out of interrupt vectors!");
-	return next_vector++;
+	return vector;
+}
+
+void
+free_irq_vector (int vector)
+{
+	int pos;
+
+	if (vector < IA64_FIRST_DEVICE_VECTOR || vector > IA64_LAST_DEVICE_VECTOR) {
+		printk(KERN_WARNING "%s: wrong device vector!\n", __FUNCTION__);
+		return;
+	}
+	pos = vector - IA64_FIRST_DEVICE_VECTOR;
+	if (!test_and_clear_bit(pos, ia64_vector_mask))
+		printk(KERN_WARNING "%s: double free!\n", __FUNCTION__);
 }
 
 extern unsigned int do_IRQ(unsigned long irq, struct pt_regs *regs);

diff -Naurp linux-2.6.8-rc1/include/asm-ia64/hw_irq.h linux-2.6.8-rc1-changed/include/asm-ia64/hw_irq.h
@@ -50,6 +50,7 @@ typedef u8 ia64_vector;
  */
 #define IA64_FIRST_DEVICE_VECTOR	0x30
 #define IA64_LAST_DEVICE_VECTOR		0xe7
+#define IA64_NUM_DEVICE_VECTORS		(IA64_LAST_DEVICE_VECTOR - IA64_FIRST_DEVICE_VECTOR + 1)
 
 #define IA64_MCA_RENDEZ_VECTOR		0xe8	/* MCA rendez interrupt */
 #define IA64_PERFMON_VECTOR		0xee	/* performanc monitor interrupt vector */

@@ -82,7 +83,9 @@ extern unsigned long ipi_base_addr;
 
 extern struct hw_interrupt_type irq_type_ia64_lsapic;	/* CPU-internal interrupt controller */
 
+extern int assign_irq_vector_nopanic (int irq);
 extern int assign_irq_vector (int irq);	/* allocate a free vector */
+extern void free_irq_vector (int vector);
 extern void ia64_send_ipi (int cpu, int vector, int delivery_mode, int redirect);
 extern void register_percpu_irq (ia64_vector vec, struct irqaction *action);
 

diff -Naurp linux-2.6.8-rc1/include/asm-ia64/iosapic.h linux-2.6.8-rc1-changed/include/asm-ia64/iosapic.h
@@ -47,6 +47,12 @@
 #define	IOSAPIC_MASK_SHIFT		16
 #define	IOSAPIC_MASK			(1<<IOSAPIC_MASK_SHIFT)
 
+/*
+ * Vector type
+ */
+#define IOSAPIC_VECTOR_EXCLUSIVE	0
+#define IOSAPIC_VECTOR_SHARABLE		1
+
 #ifndef __ASSEMBLY__
 
 #ifdef CONFIG_IOSAPIC

diff -Naurp linux-2.6.8-rc1/include/asm-ia64/irq.h linux-2.6.8-rc1-changed/include/asm-ia64/irq.h
@@ -31,6 +31,8 @@ extern void enable_irq (unsigned int);
 extern void set_irq_affinity_info (unsigned int irq, int dest, int redir);
 
 #ifdef CONFIG_SMP
+#include <linux/cpumask.h>
+extern cpumask_t get_irq_affinity_info (unsigned int irq);
 extern void move_irq(int irq);
 #else
 #define move_irq(irq)