vhost/vsock: use static minor number

Vhost-vsock is a software device so there is no probe call that causes
the driver to register its misc char device node.  This creates a
chicken and egg problem: userspace applications must open
/dev/vhost-vsock to use the driver but the file doesn't exist until the
kernel module has been loaded.

Use the devname modalias mechanism so that /dev/vhost-vsock is created
at boot.  The vhost_vsock kernel module is automatically loaded when the
first application opens /dev/host-vsock.

Note that the "reserved for local use" range in
Documentation/admin-guide/devices.txt is incorrect.  The userio driver
already occupies part of that range.  I've updated the documentation
accordingly.

Cc: device@lanana.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index c9cea2e39c218845fd9291767ca85cc4a9737c99..6b71852dadc277c638310beb63d89064024e7d5b 100644 (file)
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -369,8 +369,10 @@
                237 = /dev/loop-control Loopback control device
                238 = /dev/vhost-net    Host kernel accelerator for virtio net
                239 = /dev/uhid         User-space I/O driver support for HID subsystem
+               240 = /dev/userio       Serio driver testing device
+               241 = /dev/vhost-vsock  Host kernel driver for virtio vsock
 
-               240-254                 Reserved for local use
+               242-254                 Reserved for local use
                255                     Reserved for MISC_DYNAMIC_MINOR
 
   11 char      Raw keyboard device     (Linux/SPARC only)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 3acef3c5d8edeca06d09e4b5d7e4ddeed0c8936c..3f63e03de8e8099f1a4c1c23b5d5fdfe7eaca634 100644 (file)
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -706,7 +706,7 @@ static const struct file_operations vhost_vsock_fops = {
 };
 
 static struct miscdevice vhost_vsock_misc = {
-       .minor = MISC_DYNAMIC_MINOR,
+       .minor = VHOST_VSOCK_MINOR,
        .name = "vhost-vsock",
        .fops = &vhost_vsock_fops,
 };
@@ -778,3 +778,5 @@ module_exit(vhost_vsock_exit);
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Asias He");
 MODULE_DESCRIPTION("vhost transport for vsock ");
+MODULE_ALIAS_MISCDEV(VHOST_VSOCK_MINOR);
+MODULE_ALIAS("devname:vhost-vsock");

diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index 762b5fec338313315b0d71abcc9153a45fa43fcb..58751eae5f7723e185c126e1d424d7f7f1971696 100644 (file)
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -54,6 +54,7 @@
 #define VHOST_NET_MINOR                238
 #define UHID_MINOR             239
 #define USERIO_MINOR           240
+#define VHOST_VSOCK_MINOR      241
 #define MISC_DYNAMIC_MINOR     255
 
 struct device;