Merge tag 'pm+acpi-4.2-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management and ACPI updates from Rafael Wysocki:
 "These are fixes on top of the previous PM+ACPI pull requests
  (including one fix for a 4.1 regression) and two commits adding
  _CLS-based device enumeration support to the ACPI core and the ATA
  subsystem that waited for the latest ACPICA changes to be merged.

  Specifics:

   - Fix for an ACPI resources management regression introduced during
     the 4.1 cycle (that unfortunately went into -stable) effectively
     reverting the bad commit along with the recent fixups on top of it
     and using an alternative approach to address the underlying issue
     (Rafael J Wysocki).

   - Fix for a memory leak and an incorrect return value in an error
     code path in the ACPI LPSS (Low-Power Subsystem) driver (Rafael J
     Wysocki).

   - Fix for a leftover dangling pointer in an error code path in the
     new wakeup IRQ support code (Rafael J Wysocki).

   - Fix to prevent infinite loops (due to errors in other places) from
     happening in the core generic PM domains support code (Geert
     Uytterhoeven).

   - Hibernation documentation update/clarification (Uwe Geuder).

   - Support for _CLS-based device enumeration in the ACPI core and in
     the ATA subsystem (Suravee Suthikulpanit)"

* tag 'pm+acpi-4.2-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM / wakeirq: Avoid setting power.wakeirq too hastily
  ata: ahci_platform: Add ACPI _CLS matching
  ACPI / scan: Add support for ACPI _CLS device matching
  PM / hibernate: clarify resume documentation
  PM / Domains: Avoid infinite loops in attach/detach code
  ACPI / LPSS: Fix up acpi_lpss_create_device()
  ACPI / PNP: Reserve ACPI resources at the fs_initcall_sync stage

Documentation/power/swsusp.txt

@@ -410,8 +410,17 @@ Documentation/usb/persist.txt.
 
 Q: Can I suspend-to-disk using a swap partition under LVM?
 
-A: No. You can suspend successfully, but you'll not be able to
-resume. uswsusp should be able to work with LVM. See suspend.sf.net.
+A: Yes and No.  You can suspend successfully, but the kernel will not be able
+to resume on its own.  You need an initramfs that can recognize the resume
+situation, activate the logical volume containing the swap volume (but not
+touch any filesystems!), and eventually call
+
+echo -n "$major:$minor" > /sys/power/resume
+
+where $major and $minor are the respective major and minor device numbers of
+the swap volume.
+
+uswsusp works with LVM, too.  See http://suspend.sourceforge.net/
 
 Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
 compiled with the similar configuration files. Anyway I found that

drivers/acpi/acpi_lpss.c

@@ -352,13 +352,16 @@ static int acpi_lpss_create_device(struct acpi_device *adev,
 				pdata->mmio_size = resource_size(rentry->res);
 			pdata->mmio_base = ioremap(rentry->res->start,
 						   pdata->mmio_size);
-			if (!pdata->mmio_base)
-				goto err_out;
 			break;
 		}
 
 	acpi_dev_free_resource_list(&resource_list);
 
+	if (!pdata->mmio_base) {
+		ret = -ENOMEM;
+		goto err_out;
+	}
+
 	pdata->dev_desc = dev_desc;
 
 	if (dev_desc->setup)

drivers/acpi/osl.c

@@ -175,10 +175,14 @@ static void __init acpi_request_region (struct acpi_generic_address *gas,
 	if (!addr || !length)
 		return;
 
-	acpi_reserve_region(addr, length, gas->space_id, 0, desc);
+	/* Resources are never freed */
+	if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO)
+		request_region(addr, length, desc);
+	else if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		request_mem_region(addr, length, desc);
 }
 
-static void __init acpi_reserve_resources(void)
+static int __init acpi_reserve_resources(void)
 {
 	acpi_request_region(&acpi_gbl_FADT.xpm1a_event_block, acpi_gbl_FADT.pm1_event_length,
 		"ACPI PM1a_EVT_BLK");
@@ -207,7 +211,10 @@ static void __init acpi_reserve_resources(void)
 	if (!(acpi_gbl_FADT.gpe1_block_length & 0x1))
 		acpi_request_region(&acpi_gbl_FADT.xgpe1_block,
 			       acpi_gbl_FADT.gpe1_block_length, "ACPI GPE1_BLK");
+
+	return 0;
 }
+fs_initcall_sync(acpi_reserve_resources);
 
 void acpi_os_printf(const char *fmt, ...)
 {
@@ -1862,7 +1869,6 @@ acpi_status __init acpi_os_initialize(void)
 
 acpi_status __init acpi_os_initialize1(void)
 {
-	acpi_reserve_resources();
 	kacpid_wq = alloc_workqueue("kacpid", 0, 1);
 	kacpi_notify_wq = alloc_workqueue("kacpi_notify", 0, 1);
 	kacpi_hotplug_wq = alloc_ordered_workqueue("kacpi_hotplug", 0);

drivers/acpi/resource.c

@@ -26,7 +26,6 @@
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/ioport.h>
-#include <linux/list.h>
 #include <linux/slab.h>
 
 #ifdef CONFIG_X86
@@ -622,164 +621,3 @@ int acpi_dev_filter_resource_type(struct acpi_resource *ares,
 	return (type & types) ? 0 : 1;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_filter_resource_type);
-
-struct reserved_region {
-	struct list_head node;
-	u64 start;
-	u64 end;
-};
-
-static LIST_HEAD(reserved_io_regions);
-static LIST_HEAD(reserved_mem_regions);
-
-static int request_range(u64 start, u64 end, u8 space_id, unsigned long flags,
-			 char *desc)
-{
-	unsigned int length = end - start + 1;
-	struct resource *res;
-
-	res = space_id == ACPI_ADR_SPACE_SYSTEM_IO ?
-		request_region(start, length, desc) :
-		request_mem_region(start, length, desc);
-	if (!res)
-		return -EIO;
-
-	res->flags &= ~flags;
-	return 0;
-}
-
-static int add_region_before(u64 start, u64 end, u8 space_id,
-			     unsigned long flags, char *desc,
-			     struct list_head *head)
-{
-	struct reserved_region *reg;
-	int error;
-
-	reg = kmalloc(sizeof(*reg), GFP_KERNEL);
-	if (!reg)
-		return -ENOMEM;
-
-	error = request_range(start, end, space_id, flags, desc);
-	if (error) {
-		kfree(reg);
-		return error;
-	}
-
-	reg->start = start;
-	reg->end = end;
-	list_add_tail(&reg->node, head);
-	return 0;
-}
-
-/**
- * acpi_reserve_region - Reserve an I/O or memory region as a system resource.
- * @start: Starting address of the region.
- * @length: Length of the region.
- * @space_id: Identifier of address space to reserve the region from.
- * @flags: Resource flags to clear for the region after requesting it.
- * @desc: Region description (for messages).
- *
- * Reserve an I/O or memory region as a system resource to prevent others from
- * using it.  If the new region overlaps with one of the regions (in the given
- * address space) already reserved by this routine, only the non-overlapping
- * parts of it will be reserved.
- *
- * Returned is either 0 (success) or a negative error code indicating a resource
- * reservation problem.  It is the code of the first encountered error, but the
- * routine doesn't abort until it has attempted to request all of the parts of
- * the new region that don't overlap with other regions reserved previously.
- *
- * The resources requested by this routine are never released.
- */
-int acpi_reserve_region(u64 start, unsigned int length, u8 space_id,
-			unsigned long flags, char *desc)
-{
-	struct list_head *regions;
-	struct reserved_region *reg;
-	u64 end = start + length - 1;
-	int ret = 0, error = 0;
-
-	if (space_id == ACPI_ADR_SPACE_SYSTEM_IO)
-		regions = &reserved_io_regions;
-	else if (space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
-		regions = &reserved_mem_regions;
-	else
-		return -EINVAL;
-
-	if (list_empty(regions))
-		return add_region_before(start, end, space_id, flags, desc, regions);
-
-	list_for_each_entry(reg, regions, node)
-		if (reg->start == end + 1) {
-			/* The new region can be prepended to this one. */
-			ret = request_range(start, end, space_id, flags, desc);
-			if (!ret)
-				reg->start = start;
-
-			return ret;
-		} else if (reg->start > end) {
-			/* No overlap.  Add the new region here and get out. */
-			return add_region_before(start, end, space_id, flags,
-						 desc, &reg->node);
-		} else if (reg->end == start - 1) {
-			goto combine;
-		} else if (reg->end >= start) {
-			goto overlap;
-		}
-
-	/* The new region goes after the last existing one. */
-	return add_region_before(start, end, space_id, flags, desc, regions);
-
- overlap:
-	/*
-	 * The new region overlaps an existing one.
-	 *
-	 * The head part of the new region immediately preceding the existing
-	 * overlapping one can be combined with it right away.
-	 */
-	if (reg->start > start) {
-		error = request_range(start, reg->start - 1, space_id, flags, desc);
-		if (error)
-			ret = error;
-		else
-			reg->start = start;
-	}
-
- combine:
-	/*
-	 * The new region is adjacent to an existing one.  If it extends beyond
-	 * that region all the way to the next one, it is possible to combine
-	 * all three of them.
-	 */
-	while (reg->end < end) {
-		struct reserved_region *next = NULL;
-		u64 a = reg->end + 1, b = end;
-
-		if (!list_is_last(&reg->node, regions)) {
-			next = list_next_entry(reg, node);
-			if (next->start <= end)
-				b = next->start - 1;
-		}
-		error = request_range(a, b, space_id, flags, desc);
-		if (!error) {
-			if (next && next->start == b + 1) {
-				reg->end = next->end;
-				list_del(&next->node);
-				kfree(next);
-			} else {
-				reg->end = end;
-				break;
-			}
-		} else if (next) {
-			if (!ret)
-				ret = error;
-
-			reg = next;
-		} else {
-			break;
-		}
-	}
-
-	return ret ? ret : error;
-}
-EXPORT_SYMBOL_GPL(acpi_reserve_region);

drivers/acpi/scan.c

@@ -1019,6 +1019,29 @@ static bool acpi_of_match_device(struct acpi_device *adev,
 	return false;
 }
 
+static bool __acpi_match_device_cls(const struct acpi_device_id *id,
+				    struct acpi_hardware_id *hwid)
+{
+	int i, msk, byte_shift;
+	char buf[3];
+
+	if (!id->cls)
+		return false;
+
+	/* Apply class-code bitmask, before checking each class-code byte */
+	for (i = 1; i <= 3; i++) {
+		byte_shift = 8 * (3 - i);
+		msk = (id->cls_msk >> byte_shift) & 0xFF;
+		if (!msk)
+			continue;
+
+		sprintf(buf, "%02x", (id->cls >> byte_shift) & msk);
+		if (strncmp(buf, &hwid->id[(i - 1) * 2], 2))
+			return false;
+	}
+	return true;
+}
+
 static const struct acpi_device_id *__acpi_match_device(
 	struct acpi_device *device,
 	const struct acpi_device_id *ids,
@@ -1036,9 +1059,12 @@ static const struct acpi_device_id *__acpi_match_device(
 
 	list_for_each_entry(hwid, &device->pnp.ids, list) {
 		/* First, check the ACPI/PNP IDs provided by the caller. */
-		for (id = ids; id->id[0]; id++)
-			if (!strcmp((char *) id->id, hwid->id))
+		for (id = ids; id->id[0] || id->cls; id++) {
+			if (id->id[0] && !strcmp((char *) id->id, hwid->id))
 				return id;
+			else if (id->cls && __acpi_match_device_cls(id, hwid))
+				return id;
+		}
 
 		/*
 		 * Next, check ACPI_DT_NAMESPACE_HID and try to match the
@@ -2101,6 +2127,8 @@ static void acpi_set_pnp_ids(acpi_handle handle, struct acpi_device_pnp *pnp,
 		if (info->valid & ACPI_VALID_UID)
 			pnp->unique_id = kstrdup(info->unique_id.string,
 							GFP_KERNEL);
+		if (info->valid & ACPI_VALID_CLS)
+			acpi_add_id(pnp, info->class_code.string);
 
 		kfree(info);
 

drivers/ata/Kconfig

@@ -48,7 +48,7 @@ config ATA_VERBOSE_ERROR
 
 config ATA_ACPI
 	bool "ATA ACPI Support"
-	depends on ACPI && PCI
+	depends on ACPI
 	default y
 	help
 	  This option adds support for ATA-related ACPI objects.

drivers/ata/ahci_platform.c

@@ -20,6 +20,8 @@
 #include <linux/platform_device.h>
 #include <linux/libata.h>
 #include <linux/ahci_platform.h>
+#include <linux/acpi.h>
+#include <linux/pci_ids.h>
 #include "ahci.h"
 
 #define DRV_NAME "ahci"
@@ -79,12 +81,19 @@ static const struct of_device_id ahci_of_match[] = {
 };
 MODULE_DEVICE_TABLE(of, ahci_of_match);
 
+static const struct acpi_device_id ahci_acpi_match[] = {
+	{ ACPI_DEVICE_CLASS(PCI_CLASS_STORAGE_SATA_AHCI, 0xffffff) },
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, ahci_acpi_match);
+
 static struct platform_driver ahci_driver = {
 	.probe = ahci_probe,
 	.remove = ata_platform_remove_one,
 	.driver = {
 		.name = DRV_NAME,
 		.of_match_table = ahci_of_match,
+		.acpi_match_table = ahci_acpi_match,
 		.pm = &ahci_pm_ops,
 	},
 };

drivers/base/power/domain.c

@@ -6,6 +6,7 @@
  * This file is released under the GPLv2.
  */
 
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/io.h>
 #include <linux/platform_device.h>
@@ -19,6 +20,8 @@
 #include <linux/suspend.h>
 #include <linux/export.h>
 
+#define GENPD_RETRY_MAX_MS	250		/* Approximate */
+
 #define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\
 ({								\
 	type (*__routine)(struct device *__d); 			\
@@ -2131,6 +2134,7 @@ EXPORT_SYMBOL_GPL(of_genpd_get_from_provider);
 static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 {
 	struct generic_pm_domain *pd;
+	unsigned int i;
 	int ret = 0;
 
 	pd = pm_genpd_lookup_dev(dev);
@@ -2139,10 +2143,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 
 	dev_dbg(dev, "removing from PM domain %s\n", pd->name);
 
-	while (1) {
+	for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
 		ret = pm_genpd_remove_device(pd, dev);
 		if (ret != -EAGAIN)
 			break;
+
+		mdelay(i);
 		cond_resched();
 	}
 
@@ -2183,6 +2189,7 @@ int genpd_dev_pm_attach(struct device *dev)
 {
 	struct of_phandle_args pd_args;
 	struct generic_pm_domain *pd;
+	unsigned int i;
 	int ret;
 
 	if (!dev->of_node)
@@ -2218,10 +2225,12 @@ int genpd_dev_pm_attach(struct device *dev)
 
 	dev_dbg(dev, "adding to PM domain %s\n", pd->name);
 
-	while (1) {
+	for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
 		ret = pm_genpd_add_device(pd, dev);
 		if (ret != -EAGAIN)
 			break;
+
+		mdelay(i);
 		cond_resched();
 	}
 

drivers/base/power/wakeirq.c

@@ -45,14 +45,12 @@ static int dev_pm_attach_wake_irq(struct device *dev, int irq,
 		return -EEXIST;
 	}
 
-	dev->power.wakeirq = wirq;
-	spin_unlock_irqrestore(&dev->power.lock, flags);
-
 	err = device_wakeup_attach_irq(dev, wirq);
-	if (err)
-		return err;
+	if (!err)
+		dev->power.wakeirq = wirq;
 
-	return 0;
+	spin_unlock_irqrestore(&dev->power.lock, flags);
+	return err;
 }
 
 /**
@@ -105,10 +103,10 @@ void dev_pm_clear_wake_irq(struct device *dev)
 		return;
 
 	spin_lock_irqsave(&dev->power.lock, flags);
+	device_wakeup_detach_irq(dev);
 	dev->power.wakeirq = NULL;
 	spin_unlock_irqrestore(&dev->power.lock, flags);
 
-	device_wakeup_detach_irq(dev);
 	if (wirq->dedicated_irq)
 		free_irq(wirq->irq, wirq);
 	kfree(wirq);

drivers/base/power/wakeup.c

@@ -281,32 +281,25 @@ EXPORT_SYMBOL_GPL(device_wakeup_enable);
  * Attach a device wakeirq to the wakeup source so the device
  * wake IRQ can be configured automatically for suspend and
  * resume.
+ *
+ * Call under the device's power.lock lock.
  */
 int device_wakeup_attach_irq(struct device *dev,
 			     struct wake_irq *wakeirq)
 {
 	struct wakeup_source *ws;
-	int ret = 0;
 
-	spin_lock_irq(&dev->power.lock);
 	ws = dev->power.wakeup;
 	if (!ws) {
 		dev_err(dev, "forgot to call call device_init_wakeup?\n");
-		ret = -EINVAL;
-		goto unlock;
+		return -EINVAL;
 	}
 
-	if (ws->wakeirq) {
-		ret = -EEXIST;
-		goto unlock;
-	}
+	if (ws->wakeirq)
+		return -EEXIST;
 
 	ws->wakeirq = wakeirq;
-
-unlock:
-	spin_unlock_irq(&dev->power.lock);
-
-	return ret;
+	return 0;
 }
 
 /**
@@ -314,20 +307,16 @@ int device_wakeup_attach_irq(struct device *dev,
  * @dev: Device to handle
  *
  * Removes a device wakeirq from the wakeup source.
+ *
+ * Call under the device's power.lock lock.
  */
 void device_wakeup_detach_irq(struct device *dev)
 {
 	struct wakeup_source *ws;
 
-	spin_lock_irq(&dev->power.lock);
 	ws = dev->power.wakeup;
-	if (!ws)
-		goto unlock;
-
-	ws->wakeirq = NULL;
-
-unlock:
-	spin_unlock_irq(&dev->power.lock);
+	if (ws)
+		ws->wakeirq = NULL;
 }
 
 /**

drivers/pnp/system.c

@@ -7,7 +7,6 @@
  *	Bjorn Helgaas <bjorn.helgaas@hp.com>
  */
 
-#include <linux/acpi.h>
 #include <linux/pnp.h>
 #include <linux/device.h>
 #include <linux/init.h>
@@ -23,41 +22,25 @@ static const struct pnp_device_id pnp_dev_table[] = {
 	{"", 0}
 };
 
-#ifdef CONFIG_ACPI
-static bool __reserve_range(u64 start, unsigned int length, bool io, char *desc)
-{
-	u8 space_id = io ? ACPI_ADR_SPACE_SYSTEM_IO : ACPI_ADR_SPACE_SYSTEM_MEMORY;
-	return !acpi_reserve_region(start, length, space_id, IORESOURCE_BUSY, desc);
-}
-#else
-static bool __reserve_range(u64 start, unsigned int length, bool io, char *desc)
-{
-	struct resource *res;
-
-	res = io ? request_region(start, length, desc) :
-		request_mem_region(start, length, desc);
-	if (res) {
-		res->flags &= ~IORESOURCE_BUSY;
-		return true;
-	}
-	return false;
-}
-#endif
-
 static void reserve_range(struct pnp_dev *dev, struct resource *r, int port)
 {
 	char *regionid;
 	const char *pnpid = dev_name(&dev->dev);
 	resource_size_t start = r->start, end = r->end;
-	bool reserved;
+	struct resource *res;
 
 	regionid = kmalloc(16, GFP_KERNEL);
 	if (!regionid)
 		return;
 
 	snprintf(regionid, 16, "pnp %s", pnpid);
-	reserved = __reserve_range(start, end - start + 1, !!port, regionid);
-	if (!reserved)
+	if (port)
+		res = request_region(start, end - start + 1, regionid);
+	else
+		res = request_mem_region(start, end - start + 1, regionid);
+	if (res)
+		res->flags &= ~IORESOURCE_BUSY;
+	else
 		kfree(regionid);
 
 	/*
@@ -66,7 +49,7 @@ static void reserve_range(struct pnp_dev *dev, struct resource *r, int port)
 	 * have double reservations.
 	 */
 	dev_info(&dev->dev, "%pR %s reserved\n", r,
-		 reserved ? "has been" : "could not be");
+		 res ? "has been" : "could not be");
 }
 
 static void reserve_resources_of_dev(struct pnp_dev *dev)

include/linux/acpi.h

@@ -58,6 +58,19 @@ static inline acpi_handle acpi_device_handle(struct acpi_device *adev)
 	acpi_fwnode_handle(adev) : NULL)
 #define ACPI_HANDLE(dev)		acpi_device_handle(ACPI_COMPANION(dev))
 
+/**
+ * ACPI_DEVICE_CLASS - macro used to describe an ACPI device with
+ * the PCI-defined class-code information
+ *
+ * @_cls : the class, subclass, prog-if triple for this device
+ * @_msk : the class mask for this device
+ *
+ * This macro is used to create a struct acpi_device_id that matches a
+ * specific PCI class. The .id and .driver_data fields will be left
+ * initialized with the default value.
+ */
+#define ACPI_DEVICE_CLASS(_cls, _msk)	.cls = (_cls), .cls_msk = (_msk),
+
 static inline bool has_acpi_companion(struct device *dev)
 {
 	return is_acpi_node(dev->fwnode);
@@ -309,9 +322,6 @@ int acpi_check_region(resource_size_t start, resource_size_t n,
 
 int acpi_resources_are_enforced(void);
 
-int acpi_reserve_region(u64 start, unsigned int length, u8 space_id,
-			unsigned long flags, char *desc);
-
 #ifdef CONFIG_HIBERNATION
 void __init acpi_no_s4_hw_signature(void);
 #endif
@@ -446,6 +456,7 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *);
 #define ACPI_COMPANION(dev)		(NULL)
 #define ACPI_COMPANION_SET(dev, adev)	do { } while (0)
 #define ACPI_HANDLE(dev)		(NULL)
+#define ACPI_DEVICE_CLASS(_cls, _msk)	.cls = (0), .cls_msk = (0),
 
 struct fwnode_handle;
 
@@ -507,13 +518,6 @@ static inline int acpi_check_region(resource_size_t start, resource_size_t n,
 	return 0;
 }
 
-static inline int acpi_reserve_region(u64 start, unsigned int length,
-				      u8 space_id, unsigned long flags,
-				      char *desc)
-{
-	return -ENXIO;
-}
-
 struct acpi_table_header;
 static inline int acpi_table_parse(char *id,
 				int (*handler)(struct acpi_table_header *))

include/linux/mod_devicetable.h

@@ -189,6 +189,8 @@ struct css_device_id {
 struct acpi_device_id {
 	__u8 id[ACPI_ID_LEN];
 	kernel_ulong_t driver_data;
+	__u32 cls;
+	__u32 cls_msk;
 };
 
 #define PNP_ID_LEN	8

scripts/mod/devicetable-offsets.c

@@ -63,6 +63,8 @@ int main(void)
 
 	DEVID(acpi_device_id);
 	DEVID_FIELD(acpi_device_id, id);
+	DEVID_FIELD(acpi_device_id, cls);
+	DEVID_FIELD(acpi_device_id, cls_msk);
 
 	DEVID(pnp_device_id);
 	DEVID_FIELD(pnp_device_id, id);

scripts/mod/file2alias.c

@@ -523,12 +523,40 @@ static int do_serio_entry(const char *filename,
 }
 ADD_TO_DEVTABLE("serio", serio_device_id, do_serio_entry);
 
-/* looks like: "acpi:ACPI0003 or acpi:PNP0C0B" or "acpi:LNXVIDEO" */
+/* looks like: "acpi:ACPI0003" or "acpi:PNP0C0B" or "acpi:LNXVIDEO" or
+ *             "acpi:bbsspp" (bb=base-class, ss=sub-class, pp=prog-if)
+ *
+ * NOTE: Each driver should use one of the following : _HID, _CIDs
+ *       or _CLS. Also, bb, ss, and pp can be substituted with ??
+ *       as don't care byte.
+ */
 static int do_acpi_entry(const char *filename,
 			void *symval, char *alias)
 {
 	DEF_FIELD_ADDR(symval, acpi_device_id, id);
-	sprintf(alias, "acpi*:%s:*", *id);
+	DEF_FIELD_ADDR(symval, acpi_device_id, cls);
+	DEF_FIELD_ADDR(symval, acpi_device_id, cls_msk);
+
+	if (id && strlen((const char *)*id))
+		sprintf(alias, "acpi*:%s:*", *id);
+	else if (cls) {
+		int i, byte_shift, cnt = 0;
+		unsigned int msk;
+
+		sprintf(&alias[cnt], "acpi*:");
+		cnt = 6;
+		for (i = 1; i <= 3; i++) {
+			byte_shift = 8 * (3-i);
+			msk = (*cls_msk >> byte_shift) & 0xFF;
+			if (msk)
+				sprintf(&alias[cnt], "%02x",
+					(*cls >> byte_shift) & 0xFF);
+			else
+				sprintf(&alias[cnt], "??");
+			cnt += 2;
+		}
+		sprintf(&alias[cnt], ":*");
+	}
 	return 1;
 }
 ADD_TO_DEVTABLE("acpi", acpi_device_id, do_acpi_entry);