This patch makes blktap Do The Right Thing(TM). It allows udev to create the /dev/xen/blktap[0-9] devices.

It creates a sysfs class called "xen". This part may later be placed someplace else, but currently blktap is the only user so it is placed in the blktap code.

When blktap is initialized, a blktap0 sysfs class device is made. The other devices blktapX (X > 0) are made when the BLKTAP_IOCTL_NEWINTF ioctl is called. This way we don't flood the sysfs and /dev/xen with unnecessary devices.

I added a rule in the xen-backend.rules to allow for udev to create the blktap devices.

With this, we can really remove the code to search and create the /dev/xen/blktap[0-9]*, but I'll leave it in for now. With the use of udev, we really should remove that code as well as the code for creating the evtchn device. udev works for both of these now. But that removal will have to be in another patch.

-- Steve