virtio: set device index in common code.

Anthony Liguori points out that three different transports use the virtio code,
but each one keeps its own counter to set the virtio_device's index field.  In
theory (though not in current practice) this means that names could be
duplicated, and that risk grows as more transports are created.

So we move the selection of the unique virtio_device.index into the common code
in virtio.c, which has the side-benefit of removing duplicate code.

The only complexity is that lguest and S/390 use the index to uniquely identify
the device in case of catastrophic failure before register_virtio_device() is
called: now we use the offset within the descriptor page as a unique identifier
for the printks.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Carsten Otte <cotte@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chris Lalancette <clalance@redhat.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 59918dfc3cb7..0f3c2bb7bf35 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -2,6 +2,9 @@
 #include <linux/spinlock.h>
 #include <linux/virtio_config.h>
 
+/* Unique numbering for virtio devices. */
+static unsigned int dev_index;
+
 static ssize_t device_show(struct device *_d,
                            struct device_attribute *attr, char *buf)
 {
@@ -166,6 +169,9 @@ int register_virtio_device(struct virtio_device *dev)
         int err;
 
         dev->dev.bus = &virtio_bus;
+
+        /* Assign a unique device index and hence name. */
+        dev->index = dev_index++;
         sprintf(dev->dev.bus_id, "virtio%u", dev->index);
 
         /* We always start by resetting the device, in case a previous