[PATCH] virtio: remove virtio-pci root device

[Milton Miller <miltonm@bga.com>]

We sometimes need to map between the virtio device and
the given pci device. One such use is OS installer that
gets the boot pci device from BIOS and needs to
find the relevant block device. Since it can't,
installation fails.

Instead of creating a top-level devices/virtio-pci
directory, create each device under the corresponding
pci device node.  Symlinks to all virtio-pci
devices can be found under the pci driver link in
bus/pci/drivers/virtio-pci/devices, and all virtio
devices under drivers/bus/virtio/devices.

Signed-off-by: Milton Miller <miltonm@bga.com>
---

This is an alternative to the patch by Michael S. Tsirkin
titled "virtio-pci: add softlinks between virtio and pci"
https://patchwork.kernel.org/patch/454581/

It creates simpler code, uses less memory, and should
be even easier use by the installer as it won't have to
know a virtio symlink to follow (just follow none).

Compile tested only as I don't have kvm setup.


diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index ef8d9d5..4fb5b2b 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -96,11 +96,6 @@ static struct pci_device_id virtio_pci_id_table[] = {
 
 MODULE_DEVICE_TABLE(pci, virtio_pci_id_table);
 
-/* A PCI device has it's own struct device and so does a virtio device so
- * we create a place for the virtio devices to show up in sysfs.  I think it
- * would make more sense for virtio to not insist on having it's own device. */
-static struct device *virtio_pci_root;
-
 /* Convert a generic virtio device to our structure */
 static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
 {
@@ -629,7 +624,7 @@ static int __devinit virtio_pci_probe(struct pci_dev *pci_dev,
 	if (vp_dev == NULL)
 		return -ENOMEM;
 
-	vp_dev->vdev.dev.parent = virtio_pci_root;
+	vp_dev->vdev.dev.parent = &pci_dev->dev;
 	vp_dev->vdev.dev.release = virtio_pci_release_dev;
 	vp_dev->vdev.config = &virtio_pci_config_ops;
 	vp_dev->pci_dev = pci_dev;
@@ -717,17 +712,7 @@ static struct pci_driver virtio_pci_driver = {
 
 static int __init virtio_pci_init(void)
 {
-	int err;
-
-	virtio_pci_root = root_device_register("virtio-pci");
-	if (IS_ERR(virtio_pci_root))
-		return PTR_ERR(virtio_pci_root);
-
-	err = pci_register_driver(&virtio_pci_driver);
-	if (err)
-		root_device_unregister(virtio_pci_root);
-
-	return err;
+	return pci_register_driver(&virtio_pci_driver);
 }
 
 module_init(virtio_pci_init);
@@ -735,7 +720,6 @@ module_init(virtio_pci_init);
 static void __exit virtio_pci_exit(void)
 {
 	pci_unregister_driver(&virtio_pci_driver);
-	root_device_unregister(virtio_pci_root);
 }
 
 module_exit(virtio_pci_exit);