13 files changed, 186 insertions, 111 deletions

diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index 97991ac6f5fc..7e52295f1ecc 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -208,7 +208,7 @@ static int power_saving_thread(void *data)
 		 * the mechanism only works when all CPUs have RT task running,
 		 * as if one CPU hasn't RT task, RT task from other CPUs will
 		 * borrow CPU time from this CPU and cause RT task use > 95%
-		 * CPU time. To make 'avoid staration' work, takes a nap here.
+		 * CPU time. To make 'avoid starvation' work, takes a nap here.
 		 */
 		if (do_sleep)
 			schedule_timeout_killable(HZ * idle_pct / 100);
@@ -222,14 +222,18 @@ static struct task_struct *ps_tsks[NR_CPUS];
 static unsigned int ps_tsk_num;
 static int create_power_saving_task(void)
 {
+	int rc = -ENOMEM;
+
 	ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
 		(void *)(unsigned long)ps_tsk_num,
 		"power_saving/%d", ps_tsk_num);
-	if (ps_tsks[ps_tsk_num]) {
+	rc = IS_ERR(ps_tsks[ps_tsk_num]) ? PTR_ERR(ps_tsks[ps_tsk_num]) : 0;
+	if (!rc)
 		ps_tsk_num++;
-		return 0;
-	}
-	return -EINVAL;
+	else
+		ps_tsks[ps_tsk_num] = NULL;
+
+	return rc;
 }
 
 static void destroy_power_saving_task(void)
@@ -237,6 +241,7 @@ static void destroy_power_saving_task(void)
 	if (ps_tsk_num > 0) {
 		ps_tsk_num--;
 		kthread_stop(ps_tsks[ps_tsk_num]);
+		ps_tsks[ps_tsk_num] = NULL;
 	}
 }
 
@@ -253,7 +258,7 @@ static void set_power_saving_task_num(unsigned int num)
 	}
 }
 
-static int acpi_pad_idle_cpus(unsigned int num_cpus)
+static void acpi_pad_idle_cpus(unsigned int num_cpus)
 {
 	get_online_cpus();
 
@@ -261,7 +266,6 @@ static int acpi_pad_idle_cpus(unsigned int num_cpus)
 	set_power_saving_task_num(num_cpus);
 
 	put_online_cpus();
-	return 0;
 }
 
 static uint32_t acpi_pad_idle_cpus_num(void)
@@ -369,19 +373,21 @@ static void acpi_pad_remove_sysfs(struct acpi_device *device)
 static int acpi_pad_pur(acpi_handle handle, int *num_cpus)
 {
 	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
-	acpi_status status;
 	union acpi_object *package;
 	int rev, num, ret = -EINVAL;
 
-	status = acpi_evaluate_object(handle, "_PUR", NULL, &buffer);
-	if (ACPI_FAILURE(status))
+	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
+		return -EINVAL;
+
+	if (!buffer.length || !buffer.pointer)
 		return -EINVAL;
+
 	package = buffer.pointer;
 	if (package->type != ACPI_TYPE_PACKAGE || package->package.count != 2)
 		goto out;
 	rev = package->package.elements[0].integer.value;
 	num = package->package.elements[1].integer.value;
-	if (rev != 1)
+	if (rev != 1 || num < 0)
 		goto out;
 	*num_cpus = num;
 	ret = 0;
@@ -410,7 +416,7 @@ static void acpi_pad_ost(acpi_handle handle, int stat,
 
 static void acpi_pad_handle_notify(acpi_handle handle)
 {
-	int num_cpus, ret;
+	int num_cpus;
 	uint32_t idle_cpus;
 
 	mutex_lock(&isolated_cpus_lock);
@@ -418,12 +424,9 @@ static void acpi_pad_handle_notify(acpi_handle handle)
 		mutex_unlock(&isolated_cpus_lock);
 		return;
 	}
-	ret = acpi_pad_idle_cpus(num_cpus);
+	acpi_pad_idle_cpus(num_cpus);
 	idle_cpus = acpi_pad_idle_cpus_num();
-	if (!ret)
-		acpi_pad_ost(handle, 0, idle_cpus);
-	else
-		acpi_pad_ost(handle, 1, 0);
+	acpi_pad_ost(handle, 0, idle_cpus);
 	mutex_unlock(&isolated_cpus_lock);
 }
 
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index cf761b904e4a..a52126e46307 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -490,9 +490,14 @@ static void acpi_bus_osc_support(void)
 
 	capbuf[OSC_QUERY_TYPE] = OSC_QUERY_ENABLE;
 	capbuf[OSC_SUPPORT_TYPE] = OSC_SB_PR3_SUPPORT; /* _PR3 is in use */
-#ifdef CONFIG_ACPI_PROCESSOR_AGGREGATOR
+#if defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR) ||\
+			defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR_MODULE)
 	capbuf[OSC_SUPPORT_TYPE] |= OSC_SB_PAD_SUPPORT;
 #endif
+
+#if defined(CONFIG_ACPI_PROCESSOR) || defined(CONFIG_ACPI_PROCESSOR_MODULE)
+	capbuf[OSC_SUPPORT_TYPE] |= OSC_SB_PPC_OST_SUPPORT;
+#endif
 	if (ACPI_FAILURE(acpi_get_handle(NULL, "\\_SB", &handle)))
 		return;
 	if (ACPI_SUCCESS(acpi_run_osc(handle, &context)))
diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index fd1801bdee66..d6471bb6852f 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -201,14 +201,13 @@ unlock:
 	spin_unlock_irqrestore(&ec->curr_lock, flags);
 }
 
-static void acpi_ec_gpe_query(void *ec_cxt);
+static int acpi_ec_sync_query(struct acpi_ec *ec);
 
-static int ec_check_sci(struct acpi_ec *ec, u8 state)
+static int ec_check_sci_sync(struct acpi_ec *ec, u8 state)
 {
 	if (state & ACPI_EC_FLAG_SCI) {
 		if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
-			return acpi_os_execute(OSL_EC_BURST_HANDLER,
-				acpi_ec_gpe_query, ec);
+			return acpi_ec_sync_query(ec);
 	}
 	return 0;
 }
@@ -249,11 +248,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 {
 	unsigned long tmp;
 	int ret = 0;
-	pr_debug(PREFIX "transaction start\n");
-	/* disable GPE during transaction if storm is detected */
-	if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
-		acpi_disable_gpe(NULL, ec->gpe);
-	}
 	if (EC_FLAGS_MSI)
 		udelay(ACPI_EC_MSI_UDELAY);
 	/* start transaction */
@@ -265,20 +259,9 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 		clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
 	spin_unlock_irqrestore(&ec->curr_lock, tmp);
 	ret = ec_poll(ec);
-	pr_debug(PREFIX "transaction end\n");
 	spin_lock_irqsave(&ec->curr_lock, tmp);
 	ec->curr = NULL;
 	spin_unlock_irqrestore(&ec->curr_lock, tmp);
-	if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
-		/* check if we received SCI during transaction */
-		ec_check_sci(ec, acpi_ec_read_status(ec));
-		/* it is safe to enable GPE outside of transaction */
-		acpi_enable_gpe(NULL, ec->gpe);
-	} else if (t->irq_count > ACPI_EC_STORM_THRESHOLD) {
-		pr_info(PREFIX "GPE storm detected, "
-			"transactions will use polling mode\n");
-		set_bit(EC_FLAGS_GPE_STORM, &ec->flags);
-	}
 	return ret;
 }
 
@@ -321,7 +304,26 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 		status = -ETIME;
 		goto end;
 	}
+	pr_debug(PREFIX "transaction start\n");
+	/* disable GPE during transaction if storm is detected */
+	if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
+		acpi_disable_gpe(NULL, ec->gpe);
+	}
+
 	status = acpi_ec_transaction_unlocked(ec, t);
+
+	/* check if we received SCI during transaction */
+	ec_check_sci_sync(ec, acpi_ec_read_status(ec));
+	if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
+		msleep(1);
+		/* it is safe to enable GPE outside of transaction */
+		acpi_enable_gpe(NULL, ec->gpe);
+	} else if (t->irq_count > ACPI_EC_STORM_THRESHOLD) {
+		pr_info(PREFIX "GPE storm detected, "
+			"transactions will use polling mode\n");
+		set_bit(EC_FLAGS_GPE_STORM, &ec->flags);
+	}
+	pr_debug(PREFIX "transaction end\n");
 end:
 	if (ec->global_lock)
 		acpi_release_global_lock(glk);
@@ -443,7 +445,7 @@ int ec_transaction(u8 command,
 
 EXPORT_SYMBOL(ec_transaction);
 
-static int acpi_ec_query(struct acpi_ec *ec, u8 * data)
+static int acpi_ec_query_unlocked(struct acpi_ec *ec, u8 * data)
 {
 	int result;
 	u8 d;
@@ -452,20 +454,16 @@ static int acpi_ec_query(struct acpi_ec *ec, u8 * data)
 				.wlen = 0, .rlen = 1};
 	if (!ec || !data)
 		return -EINVAL;
-
 	/*
 	 * Query the EC to find out which _Qxx method we need to evaluate.
 	 * Note that successful completion of the query causes the ACPI_EC_SCI
 	 * bit to be cleared (and thus clearing the interrupt source).
 	 */
-
-	result = acpi_ec_transaction(ec, &t);
+	result = acpi_ec_transaction_unlocked(ec, &t);
 	if (result)
 		return result;
-
 	if (!d)
 		return -ENODATA;
-
 	*data = d;
 	return 0;
 }
@@ -509,43 +507,79 @@ void acpi_ec_remove_query_handler(struct acpi_ec *ec, u8 query_bit)
 
 EXPORT_SYMBOL_GPL(acpi_ec_remove_query_handler);
 
-static void acpi_ec_gpe_query(void *ec_cxt)
+static void acpi_ec_run(void *cxt)
 {
-	struct acpi_ec *ec = ec_cxt;
-	u8 value = 0;
-	struct acpi_ec_query_handler *handler, copy;
-
-	if (!ec || acpi_ec_query(ec, &value))
+	struct acpi_ec_query_handler *handler = cxt;
+	if (!handler)
 		return;
-	mutex_lock(&ec->lock);
+	pr_debug(PREFIX "start query execution\n");
+	if (handler->func)
+		handler->func(handler->data);
+	else if (handler->handle)
+		acpi_evaluate_object(handler->handle, NULL, NULL, NULL);
+	pr_debug(PREFIX "stop query execution\n");
+	kfree(handler);
+}
+
+static int acpi_ec_sync_query(struct acpi_ec *ec)
+{
+	u8 value = 0;
+	int status;
+	struct acpi_ec_query_handler *handler, *copy;
+	if ((status = acpi_ec_query_unlocked(ec, &value)))
+		return status;
 	list_for_each_entry(handler, &ec->list, node) {
 		if (value == handler->query_bit) {
 			/* have custom handler for this bit */
-			memcpy(&copy, handler, sizeof(copy));
-			mutex_unlock(&ec->lock);
-			if (copy.func) {
-				copy.func(copy.data);
-			} else if (copy.handle) {
-				acpi_evaluate_object(copy.handle, NULL, NULL, NULL);
-			}
-			return;
+			copy = kmalloc(sizeof(*handler), GFP_KERNEL);
+			if (!copy)
+				return -ENOMEM;
+			memcpy(copy, handler, sizeof(*copy));
+			pr_debug(PREFIX "push query execution (0x%2x) on queue\n", value);
+			return acpi_os_execute((copy->func) ?
+				OSL_NOTIFY_HANDLER : OSL_GPE_HANDLER,
+				acpi_ec_run, copy);
 		}
 	}
+	return 0;
+}
+
+static void acpi_ec_gpe_query(void *ec_cxt)
+{
+	struct acpi_ec *ec = ec_cxt;
+	if (!ec)
+		return;
+	mutex_lock(&ec->lock);
+	acpi_ec_sync_query(ec);
 	mutex_unlock(&ec->lock);
 }
 
+static void acpi_ec_gpe_query(void *ec_cxt);
+
+static int ec_check_sci(struct acpi_ec *ec, u8 state)
+{
+	if (state & ACPI_EC_FLAG_SCI) {
+		if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
+			pr_debug(PREFIX "push gpe query to the queue\n");
+			return acpi_os_execute(OSL_NOTIFY_HANDLER,
+				acpi_ec_gpe_query, ec);
+		}
+	}
+	return 0;
+}
+
 static u32 acpi_ec_gpe_handler(void *data)
 {
 	struct acpi_ec *ec = data;
-	u8 status;
 
 	pr_debug(PREFIX "~~~> interrupt\n");
-	status = acpi_ec_read_status(ec);
 
-	advance_transaction(ec, status);
-	if (ec_transaction_done(ec) && (status & ACPI_EC_FLAG_IBF) == 0)
+	advance_transaction(ec, acpi_ec_read_status(ec));
+	if (ec_transaction_done(ec) &&
+	    (acpi_ec_read_status(ec) & ACPI_EC_FLAG_IBF) == 0) {
 		wake_up(&ec->wait);
-	ec_check_sci(ec, status);
+		ec_check_sci(ec, acpi_ec_read_status(ec));
+	}
 	return ACPI_INTERRUPT_HANDLED;
 }
 
diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
index 394ae89409c2..04b0f007c9b7 100644
--- a/drivers/acpi/pci_link.c
+++ b/drivers/acpi/pci_link.c
@@ -56,7 +56,7 @@ ACPI_MODULE_NAME("pci_link");
 static int acpi_pci_link_add(struct acpi_device *device);
 static int acpi_pci_link_remove(struct acpi_device *device, int type);
 
-static struct acpi_device_id link_device_ids[] = {
+static const struct acpi_device_id link_device_ids[] = {
 	{"PNP0C0F", 0},
 	{"", 0},
 };
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 101cce3681d1..64f55b6db73c 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -46,7 +46,7 @@ static int acpi_pci_root_add(struct acpi_device *device);
 static int acpi_pci_root_remove(struct acpi_device *device, int type);
 static int acpi_pci_root_start(struct acpi_device *device);
 
-static struct acpi_device_id root_device_ids[] = {
+static const struct acpi_device_id root_device_ids[] = {
 	{"PNP0A03", 0},
 	{"", 0},
 };
diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index 22b297916519..0f30c3c1eea4 100644
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -65,7 +65,7 @@ static int acpi_power_remove(struct acpi_device *device, int type);
 static int acpi_power_resume(struct acpi_device *device);
 static int acpi_power_open_fs(struct inode *inode, struct file *file);
 
-static struct acpi_device_id power_device_ids[] = {
+static const struct acpi_device_id power_device_ids[] = {
 	{ACPI_POWER_HID, 0},
 	{"", 0},
 };
diff --git a/drivers/acpi/power_meter.c b/drivers/acpi/power_meter.c
index 2ef7030a0c28..dc4ffadf8122 100644
--- a/drivers/acpi/power_meter.c
+++ b/drivers/acpi/power_meter.c
@@ -64,7 +64,7 @@ static int can_cap_in_hardware(void)
 	return force_cap_on || cap_in_hardware;
 }
 
-static struct acpi_device_id power_meter_ids[] = {
+static const struct acpi_device_id power_meter_ids[] = {
 	{"ACPI000D", 0},
 	{"", 0},
 };
@@ -534,6 +534,7 @@ static void remove_domain_devices(struct acpi_power_meter_resource *resource)
 
 	kfree(resource->domain_devices);
 	kobject_put(resource->holders_dir);
+	resource->num_domain_devices = 0;
 }
 
 static int read_domain_devices(struct acpi_power_meter_resource *resource)
@@ -740,7 +741,6 @@ skip_unsafe_cap:
 
 	return res;
 error:
-	remove_domain_devices(resource);
 	remove_attrs(resource);
 	return res;
 }
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index d1676b1754d9..7c0441f63b39 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -305,6 +305,28 @@ static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr)
 	pr->power.states[ACPI_STATE_C2].latency = acpi_gbl_FADT.C2latency;
 	pr->power.states[ACPI_STATE_C3].latency = acpi_gbl_FADT.C3latency;
 
+	/*
+	 * FADT specified C2 latency must be less than or equal to
+	 * 100 microseconds.
+	 */
+	if (acpi_gbl_FADT.C2latency > ACPI_PROCESSOR_MAX_C2_LATENCY) {
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+			"C2 latency too large [%d]\n", acpi_gbl_FADT.C2latency));
+		/* invalidate C2 */
+		pr->power.states[ACPI_STATE_C2].address = 0;
+	}
+
+	/*
+	 * FADT supplied C3 latency must be less than or equal to
+	 * 1000 microseconds.
+	 */
+	if (acpi_gbl_FADT.C3latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+			"C3 latency too large [%d]\n", acpi_gbl_FADT.C3latency));
+		/* invalidate C3 */
+		pr->power.states[ACPI_STATE_C3].address = 0;
+	}
+
 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 			  "lvl2[0x%08x] lvl3[0x%08x]\n",
 			  pr->power.states[ACPI_STATE_C2].address,
@@ -494,33 +516,6 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr)
 	return status;
 }
 
-static void acpi_processor_power_verify_c2(struct acpi_processor_cx *cx)
-{
-
-	if (!cx->address)
-		return;
-
-	/*
-	 * C2 latency must be less than or equal to 100
-	 * microseconds.
-	 */
-	else if (cx->latency > ACPI_PROCESSOR_MAX_C2_LATENCY) {
-		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
-				  "latency too large [%d]\n", cx->latency));
-		return;
-	}
-
-	/*
-	 * Otherwise we've met all of our C2 requirements.
-	 * Normalize the C2 latency to expidite policy
-	 */
-	cx->valid = 1;
-
-	cx->latency_ticks = cx->latency;
-
-	return;
-}
-
 static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
 					   struct acpi_processor_cx *cx)
 {
@@ -532,16 +527,6 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
 		return;
 
 	/*
-	 * C3 latency must be less than or equal to 1000
-	 * microseconds.
-	 */
-	else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
-		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
-				  "latency too large [%d]\n", cx->latency));
-		return;
-	}
-
-	/*
 	 * PIIX4 Erratum #18: We don't support C3 when Type-F (fast)
 	 * DMA transfers are used by any ISA device to avoid livelock.
 	 * Note that we could disable Type-F DMA (as recommended by
@@ -629,7 +614,10 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
 			break;
 
 		case ACPI_STATE_C2:
-			acpi_processor_power_verify_c2(cx);
+			if (!cx->address)
+				break;
+			cx->valid = 1; 
+			cx->latency_ticks = cx->latency; /* Normalize latency */
 			break;
 
 		case ACPI_STATE_C3:
diff --git a/drivers/acpi/processor_pdc.c b/drivers/acpi/processor_pdc.c
index f3364371207e..7247819dbd80 100644
--- a/drivers/acpi/processor_pdc.c
+++ b/drivers/acpi/processor_pdc.c
@@ -174,7 +174,7 @@ early_init_pdc(acpi_handle handle, u32 lvl, void *context, void **rv)
 	return AE_OK;
 }
 
-void acpi_early_processor_set_pdc(void)
+void __init acpi_early_processor_set_pdc(void)
 {
 	/*
 	 * Check whether the system is DMI table. If yes, OSPM
diff --git a/drivers/acpi/processor_thermal.c b/drivers/acpi/processor_thermal.c
index 140c5c5b423c..6deafb4aa0da 100644
--- a/drivers/acpi/processor_thermal.c
+++ b/drivers/acpi/processor_thermal.c
@@ -443,8 +443,7 @@ struct thermal_cooling_device_ops processor_cooling_ops = {
 #ifdef CONFIG_ACPI_PROCFS
 static int acpi_processor_limit_seq_show(struct seq_file *seq, void *offset)
 {
-	struct acpi_processor *pr = (struct acpi_processor *)seq->private;
-
+	struct acpi_processor *pr = seq->private;
 
 	if (!pr)
 		goto end;
diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c
index 52b9db8afc20..b16ddbf23a9c 100644
--- a/drivers/acpi/sbs.c
+++ b/drivers/acpi/sbs.c
@@ -822,7 +822,10 @@ static int acpi_battery_add(struct acpi_sbs *sbs, int id)
 
 static void acpi_battery_remove(struct acpi_sbs *sbs, int id)
 {
+#if defined(CONFIG_ACPI_SYSFS_POWER) || defined(CONFIG_ACPI_PROCFS_POWER)
 	struct acpi_battery *battery = &sbs->battery[id];
+#endif
+
 #ifdef CONFIG_ACPI_SYSFS_POWER
 	if (battery->bat.dev) {
 		if (battery->have_sysfs_alarm)
diff --git a/drivers/acpi/sbshc.c b/drivers/acpi/sbshc.c
index d9339806df45..fd09229282ea 100644
--- a/drivers/acpi/sbshc.c
+++ b/drivers/acpi/sbshc.c
@@ -242,7 +242,7 @@ static int smbus_alarm(void *context)
 		case ACPI_SBS_CHARGER:
 		case ACPI_SBS_MANAGER:
 		case ACPI_SBS_BATTERY:
-			acpi_os_execute(OSL_GPE_HANDLER,
+			acpi_os_execute(OSL_NOTIFY_HANDLER,
 					acpi_smbus_callback, hc);
 		default:;
 	}
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 72e76b4b6538..b765790b32be 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -78,6 +78,13 @@ MODULE_LICENSE("GPL");
 static int brightness_switch_enabled = 1;
 module_param(brightness_switch_enabled, bool, 0644);
 
+/*
+ * By default, we don't allow duplicate ACPI video bus devices
+ * under the same VGA controller
+ */
+static int allow_duplicates;
+module_param(allow_duplicates, bool, 0644);
+
 static int register_count = 0;
 static int acpi_video_bus_add(struct acpi_device *device);
 static int acpi_video_bus_remove(struct acpi_device *device, int type);
@@ -2239,11 +2246,47 @@ static int acpi_video_resume(struct acpi_device *device)
 	return AE_OK;
 }
 
+static acpi_status
+acpi_video_bus_match(acpi_handle handle, u32 level, void *context,
+			void **return_value)
+{
+	struct acpi_device *device = context;
+	struct acpi_device *sibling;
+	int result;
+
+	if (handle == device->handle)
+		return AE_CTRL_TERMINATE;
+
+	result = acpi_bus_get_device(handle, &sibling);
+	if (result)
+		return AE_OK;
+
+	if (!strcmp(acpi_device_name(sibling), ACPI_VIDEO_BUS_NAME))
+			return AE_ALREADY_EXISTS;
+
+	return AE_OK;
+}
+
 static int acpi_video_bus_add(struct acpi_device *device)
 {
 	struct acpi_video_bus *video;
 	struct input_dev *input;
 	int error;
+	acpi_status status;
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE,
+				device->parent->handle, 1,
+				acpi_video_bus_match, NULL,
+				device, NULL);
+	if (status == AE_ALREADY_EXISTS) {
+		printk(KERN_WARNING FW_BUG
+			"Duplicate ACPI video bus devices for the"
+			" same VGA controller, please try module "
+			"parameter \"video.allow_duplicates=1\""
+			"if the current driver doesn't work.\n");
+		if (!allow_duplicates)
+			return -ENODEV;
+	}
 
 	video = kzalloc(sizeof(struct acpi_video_bus), GFP_KERNEL);
 	if (!video)