[PATCH v3 3/3] vfio/pci: Continue to refactor vfio_pci_core_do_io_rw

[Gerd Bayer <gbayer@xxxxxxxxxxxxx>]

Convert if-elseif-chain into switch-case.
Separate out and generalize the code from the if-clauses so the result
can be used in the switch statement.

Signed-off-by: Gerd Bayer <gbayer@xxxxxxxxxxxxx>
---
 drivers/vfio/pci/vfio_pci_rdwr.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 8ed06edaee23..634c00b03c71 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -131,6 +131,20 @@ VFIO_IORDWR(32)
 VFIO_IORDWR(64)
 #endif
 
+static int fill_size(size_t fillable, loff_t off)
+{
+	unsigned int fill_size;
+#if defined(ioread64) && defined(iowrite64)
+	for (fill_size = 8; fill_size >= 0; fill_size /= 2) {
+#else
+	for (fill_size = 4; fill_size >= 0; fill_size /= 2) {
+#endif /* defined(ioread64) && defined(iowrite64) */
+		if (fillable >= fill_size && !(off % fill_size))
+			return fill_size;
+	}
+	return -1;
+}
+
 /*
  * Read or write from an __iomem region (MMIO or I/O port) with an excluded
  * range which is inaccessible.  The excluded range drops writes and fills
@@ -155,34 +169,38 @@ ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
 		else
 			fillable = 0;
 
+		switch (fill_size(fillable, off)) {
 #if defined(ioread64) && defined(iowrite64)
-		if (fillable >= 8 && !(off % 8)) {
+		case 8:
 			ret = vfio_pci_core_iordwr64(vdev, iswrite, test_mem,
 						     io, buf, off, &filled);
 			if (ret)
 				return ret;
+			break;
 
-		} else
 #endif /* defined(ioread64) && defined(iowrite64) */
-		if (fillable >= 4 && !(off % 4)) {
+		case 4:
 			ret = vfio_pci_core_iordwr32(vdev, iswrite, test_mem,
 						     io, buf, off, &filled);
 			if (ret)
 				return ret;
+			break;
 
-		} else if (fillable >= 2 && !(off % 2)) {
+		case 2:
 			ret = vfio_pci_core_iordwr16(vdev, iswrite, test_mem,
 						     io, buf, off, &filled);
 			if (ret)
 				return ret;
+			break;
 
-		} else if (fillable) {
+		case 1:
 			ret = vfio_pci_core_iordwr8(vdev, iswrite, test_mem,
 						    io, buf, off, &filled);
 			if (ret)
 				return ret;
+			break;
 
-		} else {
+		default:
 			/* Fill reads with -1, drop writes */
 			filled = min(count, (size_t)(x_end - off));
 			if (!iswrite) {
-- 
2.44.0