vfio-pci: Cleanup read/write functions

The read and write functions are nearly identical, combine them
and convert to a switch statement.  This also makes it easy to
narrow the scope of when we use the io/mem accessors in case new
regions are added.
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci.c

@@ -366,8 +366,8 @@ static long vfio_pci_ioctl(void *device_data,
 	return -ENOTTY;
 }
 
-static ssize_t vfio_pci_read(void *device_data, char __user *buf,
-			     size_t count, loff_t *ppos)
+static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
+			   size_t count, loff_t *ppos, bool iswrite)
 {
 	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
 	struct vfio_pci_device *vdev = device_data;
@@ -376,42 +376,41 @@ static ssize_t vfio_pci_read(void *device_data, char __user *buf,
 	if (index >= VFIO_PCI_NUM_REGIONS)
 		return -EINVAL;
 
-	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
-		return vfio_pci_config_readwrite(vdev, buf, count, ppos, false);
-	else if (index == VFIO_PCI_ROM_REGION_INDEX)
-		return vfio_pci_mem_readwrite(vdev, buf, count, ppos, false);
-	else if (pci_resource_flags(pdev, index) & IORESOURCE_IO)
-		return vfio_pci_io_readwrite(vdev, buf, count, ppos, false);
-	else if (pci_resource_flags(pdev, index) & IORESOURCE_MEM)
+	switch (index) {
+	case VFIO_PCI_CONFIG_REGION_INDEX:
+		return vfio_pci_config_readwrite(vdev, buf, count,
+						 ppos, iswrite);
+	case VFIO_PCI_ROM_REGION_INDEX:
+		if (iswrite)
+			return -EINVAL;
 		return vfio_pci_mem_readwrite(vdev, buf, count, ppos, false);
 
+	case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
+	{
+		unsigned long flags = pci_resource_flags(pdev, index);
+
+		if (flags & IORESOURCE_IO)
+			return vfio_pci_io_readwrite(vdev, buf, count,
+						     ppos, iswrite);
+		if (flags & IORESOURCE_MEM)
+			return vfio_pci_mem_readwrite(vdev, buf, count,
+						      ppos, iswrite);
+	}
+	}
+
 	return -EINVAL;
 }
 
+static ssize_t vfio_pci_read(void *device_data, char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	return vfio_pci_rw(device_data, buf, count, ppos, false);
+}
+
 static ssize_t vfio_pci_write(void *device_data, const char __user *buf,
 			      size_t count, loff_t *ppos)
 {
-	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
-	struct vfio_pci_device *vdev = device_data;
-	struct pci_dev *pdev = vdev->pdev;
-
-	if (index >= VFIO_PCI_NUM_REGIONS)
-		return -EINVAL;
-
-	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
-		return vfio_pci_config_readwrite(vdev, (char __user *)buf,
-						 count, ppos, true);
-	else if (index == VFIO_PCI_ROM_REGION_INDEX)
-		return -EINVAL;
-	else if (pci_resource_flags(pdev, index) & IORESOURCE_IO)
-		return vfio_pci_io_readwrite(vdev, (char __user *)buf,
-					     count, ppos, true);
-	else if (pci_resource_flags(pdev, index) & IORESOURCE_MEM) {
-		return vfio_pci_mem_readwrite(vdev, (char __user *)buf,
-					      count, ppos, true);
-	}
-
-	return -EINVAL;
+	return vfio_pci_rw(device_data, buf, count, ppos, true);
 }
 
 static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)