vhost/vsock: use static minor number (f4660cc9) · Commits · 戴 / test

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>

Documentation/admin-guide/devices.txt

+3 −1

Original line number	Diff line number	Diff line
		@@ -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)

drivers/vhost/vsock.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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");

include/linux/miscdevice.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

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