4 files changed, 57 insertions, 21 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 84ec9c8..e5ae3a0 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -329,8 +329,8 @@ static int pci_default_resume(struct pci_dev *pci_dev)
 	/* restore the PCI config space */
 	pci_restore_state(pci_dev);
 	/* if the device was enabled before suspend, reenable */
-	if (pci_dev->is_enabled)
-		retval = pci_enable_device(pci_dev);
+	if (atomic_read(&pci_dev->enable_cnt))
+		retval = __pci_enable_device(pci_dev);
 	/* if the device was busmaster before the suspend, make it busmaster again */
 	if (pci_dev->is_busmaster)
 		pci_set_master(pci_dev);
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index f952bfe..7a94076 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -42,7 +42,6 @@ pci_config_attr(subsystem_vendor, "0x%04x\n");
 pci_config_attr(subsystem_device, "0x%04x\n");
 pci_config_attr(class, "0x%06x\n");
 pci_config_attr(irq, "%u\n");
-pci_config_attr(is_enabled, "%u\n");
 
 static ssize_t broken_parity_status_show(struct device *dev,
 					 struct device_attribute *attr,
@@ -112,26 +111,36 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
 		       (u8)(pci_dev->class >> 16), (u8)(pci_dev->class >> 8),
 		       (u8)(pci_dev->class));
 }
-static ssize_t
-is_enabled_store(struct device *dev, struct device_attribute *attr,
-		const char *buf, size_t count)
+
+static ssize_t is_enabled_store(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t count)
 {
+	ssize_t result = -EINVAL;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	int retval = 0;
 
 	/* this can crash the machine when done on the "wrong" device */
 	if (!capable(CAP_SYS_ADMIN))
 		return count;
 
-	if (*buf == '0')
-		pci_disable_device(pdev);
+	if (*buf == '0') {
+		if (atomic_read(&pdev->enable_cnt) != 0)
+			pci_disable_device(pdev);
+		else
+			result = -EIO;
+	} else if (*buf == '1')
+		result = pci_enable_device(pdev);
+
+	return result < 0 ? result : count;
+}
 
-	if (*buf == '1')
-		retval = pci_enable_device(pdev);
+static ssize_t is_enabled_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pdev;
 
-	if (retval)
-		return retval;
-	return count;
+	pdev = to_pci_dev (dev);
+	return sprintf (buf, "%u\n", atomic_read(&pdev->enable_cnt));
 }
 
 static ssize_t
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4279917..5a14b73 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -612,30 +612,51 @@ pci_enable_device_bars(struct pci_dev *dev, int bars)
 }
 
 /**
- * pci_enable_device - Initialize device before it's used by a driver.
+ * __pci_enable_device - Initialize device before it's used by a driver.
  * @dev: PCI device to be initialized
  *
  *  Initialize device before it's used by a driver. Ask low-level code
  *  to enable I/O and memory. Wake up the device if it was suspended.
  *  Beware, this function can fail.
+ *
+ * Note this function is a backend and is not supposed to be called by
+ * normal code, use pci_enable_device() instead.
  */
 int
-pci_enable_device(struct pci_dev *dev)
+__pci_enable_device(struct pci_dev *dev)
 {
 	int err;
 
-	if (dev->is_enabled)
-		return 0;
-
 	err = pci_enable_device_bars(dev, (1 << PCI_NUM_RESOURCES) - 1);
 	if (err)
 		return err;
 	pci_fixup_device(pci_fixup_enable, dev);
-	dev->is_enabled = 1;
 	return 0;
 }
 
 /**
+ * pci_enable_device - Initialize device before it's used by a driver.
+ * @dev: PCI device to be initialized
+ *
+ *  Initialize device before it's used by a driver. Ask low-level code
+ *  to enable I/O and memory. Wake up the device if it was suspended.
+ *  Beware, this function can fail.
+ *
+ *  Note we don't actually enable the device many times if we call
+ *  this function repeatedly (we just increment the count).
+ */
+int pci_enable_device(struct pci_dev *dev)
+{
+	int result;
+	if (atomic_add_return(1, &dev->enable_cnt) > 1)
+		return 0;		/* already enabled */
+	result = __pci_enable_device(dev);
+	if (result < 0)
+		atomic_dec(&dev->enable_cnt);
+	return result;
+}
+
+/**
  * pcibios_disable_device - disable arch specific PCI resources for device dev
  * @dev: the PCI device to disable
  *
@@ -651,12 +672,18 @@ void __attribute__ ((weak)) pcibios_disable_device (struct pci_dev *dev) {}
  *
  * Signal to the system that the PCI device is not in use by the system
  * anymore.  This only involves disabling PCI bus-mastering, if active.
+ *
+ * Note we don't actually disable the device until all callers of
+ * pci_device_enable() have called pci_device_disable().
  */
 void
 pci_disable_device(struct pci_dev *dev)
 {
 	u16 pci_command;
 
+	if (atomic_sub_return(1, &dev->enable_cnt) != 0)
+		return;
+
 	if (dev->msi_enabled)
 		disable_msi_mode(dev, pci_find_capability(dev, PCI_CAP_ID_MSI),
 			PCI_CAP_ID_MSI);
@@ -672,7 +699,6 @@ pci_disable_device(struct pci_dev *dev)
 	dev->is_busmaster = 0;
 
 	pcibios_disable_device(dev);
-	dev->is_enabled = 0;
 }
 
 /**
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 6bf327d..398852f 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -1,5 +1,6 @@
 /* Functions internal to the PCI core code */
 
+extern int __must_check __pci_enable_device(struct pci_dev *);
 extern int pci_uevent(struct device *dev, char **envp, int num_envp,
 		      char *buffer, int buffer_size);
 extern int pci_create_sysfs_dev_files(struct pci_dev *pdev);