virtio: console: Associate each port with a char device

The char device will be used as an interface by applications on the
guest to communicate with apps on the host.

The devices created are placed in /dev/vportNpn where N is the
virtio-console device number and n is the port number for that device.

One dynamic major device number is allocated for each device and minor
numbers are allocated for the ports contained within that device.

The file operation for the char devs will be added in the following
commits.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index e023682be2c4..3141dd3b6e53 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -666,6 +666,14 @@ config VIRTIO_CONSOLE
         help
           Virtio console for use with lguest and other hypervisors.
 
+          Also serves as a general-purpose serial device for data
+          transfer between the guest and host.  Character devices at
+          /dev/vportNpn will be created when corresponding ports are
+          found, where N is the device number and n is the port number
+          within that device.  If specified by the host, a sysfs
+          attribute called 'name' will be populated with a name for
+          the port which can be used by udev scripts to create a
+          symlink to the device.
 
 config HVCS
         tristate "IBM Hypervisor Virtual Console Server support"