ACPI: scan: Use unique number for instance_no

The decrementation of acpi_device_bus_id->instance_no
in acpi_device_del() is incorrect, because it may cause
a duplicate instance number to be allocated next time
a device with the same acpi_device_bus_id is added.

Replace above mentioned approach by using IDA framework.

While at it, define the instance range to be [0, 4096).

Fixes: e49bd2dd5a50 ("ACPI: use PNPID:instance_no as bus_id of ACPI device")
Fixes: ca9dc8d42b30 ("ACPI / scan: Fix acpi_bus_id_list bookkeeping")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: 4.10+ <stable@vger.kernel.org> # 4.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 28 insertions, 5 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index a184529d8fa4..84bb7c1929f1 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -479,9 +479,8 @@ static void acpi_device_del(struct acpi_device *device)
 	list_for_each_entry(acpi_device_bus_id, &acpi_bus_id_list, node)
 		if (!strcmp(acpi_device_bus_id->bus_id,
 			    acpi_device_hid(device))) {
-			if (acpi_device_bus_id->instance_no > 0)
-				acpi_device_bus_id->instance_no--;
-			else {
+			ida_simple_remove(&acpi_device_bus_id->instance_ida, device->pnp.instance_no);
+			if (ida_is_empty(&acpi_device_bus_id->instance_ida)) {
 				list_del(&acpi_device_bus_id->node);
 				kfree_const(acpi_device_bus_id->bus_id);
 				kfree(acpi_device_bus_id);
@@ -631,6 +630,21 @@ static struct acpi_device_bus_id *acpi_device_bus_id_match(const char *dev_id)
 	return NULL;
 }
 
+static int acpi_device_set_name(struct acpi_device *device,
+				struct acpi_device_bus_id *acpi_device_bus_id)
+{
+	struct ida *instance_ida = &acpi_device_bus_id->instance_ida;
+	int result;
+
+	result = ida_simple_get(instance_ida, 0, ACPI_MAX_DEVICE_INSTANCES, GFP_KERNEL);
+	if (result < 0)
+		return result;
+
+	device->pnp.instance_no = result;
+	dev_set_name(&device->dev, "%s:%02x", acpi_device_bus_id->bus_id, result);
+	return 0;
+}
+
 int acpi_device_add(struct acpi_device *device,
 		    void (*release)(struct device *))
 {
@@ -665,7 +679,9 @@ int acpi_device_add(struct acpi_device *device,
 
 	acpi_device_bus_id = acpi_device_bus_id_match(acpi_device_hid(device));
 	if (acpi_device_bus_id) {
-		acpi_device_bus_id->instance_no++;
+		result = acpi_device_set_name(device, acpi_device_bus_id);
+		if (result)
+			goto err_unlock;
 	} else {
 		acpi_device_bus_id = kzalloc(sizeof(*acpi_device_bus_id),
 					     GFP_KERNEL);
@@ -681,9 +697,16 @@ int acpi_device_add(struct acpi_device *device,
 			goto err_unlock;
 		}
 
+		ida_init(&acpi_device_bus_id->instance_ida);
+
+		result = acpi_device_set_name(device, acpi_device_bus_id);
+		if (result) {
+			kfree(acpi_device_bus_id);
+			goto err_unlock;
+		}
+
 		list_add_tail(&acpi_device_bus_id->node, &acpi_bus_id_list);
 	}
-	dev_set_name(&device->dev, "%s:%02x", acpi_device_bus_id->bus_id, acpi_device_bus_id->instance_no);
 
 	if (device->parent)
 		list_add_tail(&device->node, &device->parent->children);