kernel/linux.git/include/linux/miscdevice.h, branch v2.6.34

vhost_net: a kernel-level virtio server

2010-01-15T09:43:29+00:00

What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds in userspace) - write logging is supported (good for migration) - support memory table and not just an offset (needed for kvm) common virtio related code has been put in a separate file vhost.c and can be made into a separate module if/when more backends appear. I used Rusty's lguest.c as the source for developing this part : this supplied me with witty comments I wouldn't be able to write myself. What it is not: vhost net is not a bus, and not a generic new system call. No assumptions are made on how guest performs hypercalls. Userspace hypervisors are supported as well as kvm. How it works: Basically, we connect virtio frontend (configured by userspace) to a backend. The backend could be a network device, or a tap device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. Compared to userspace, people reported improved latency (as I save up to 4 system calls per packet), as well as better bandwidth and CPU utilization. Features that I plan to look at in the future: - mergeable buffers - zero copy - scalability tuning: figure out the best threading model to use Note on RCU usage (this is also documented in vhost.h, near private_pointer which is the value protected by this variant of RCU): what is happening is that the rcu_dereference() is being used in a workqueue item. The role of rcu_read_lock() is taken on by the start of execution of the workqueue item, of rcu_read_unlock() by the end of execution of the workqueue item, and of synchronize_rcu() by flush_workqueue()/flush_work(). In the future we might need to apply some gcc attribute or sparse annotation to the function passed to INIT_WORK(). Paul's ack below is for this RCU usage. (Includes fixes by Alan Cox , David L Stevens , Chris Wright ) Acked-by: Rusty Russell Acked-by: Arnd Bergmann Acked-by: "Paul E. McKenney" Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller

Driver-Core: extend devnode callbacks to provide permissions

2009-09-19T19:50:38+00:00

This allows subsytems to provide devtmpfs with non-default permissions for the device node. Instead of the default mode of 0600, null, zero, random, urandom, full, tty, ptmx now have a mode of 0666, which allows non-privileged processes to access standard device nodes in case no other userspace process applies the expected permissions. This also fixes a wrong assignment in pktcdvd and a checkpatch.pl complain. Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman

Driver Core: misc: add nodename support for misc devices.

2009-06-16T04:30:25+00:00

This adds support for misc devices to report their requested nodename to userspace. It also updates a number of misc drivers to provide the needed subdirectory and device name to be used for them. Signed-off-by: Kay Sievers Signed-off-by: Jan Blunck Signed-off-by: Greg Kroah-Hartman

[SCSI] mpt2sas: add MPT2SAS_MINOR(221) to miscdevice.h

2009-03-13T20:57:40+00:00

Signed-off-by: Eric Moore Signed-off-by: James Bottomley

fuse: move FUSE_MINOR to miscdevice.h

2008-11-26T11:03:54+00:00

Move FUSE_MINOR to miscdevice.h. While at it, de-uglify the file. Signed-off-by: Tejun Heo Signed-off-by: Miklos Szeredi

PM: Remove destroy_suspended_device()

2008-04-20T02:10:28+00:00

After 2.6.24 there was a plan to make the PM core acquire all device semaphores during a suspend/hibernation to protect itself from concurrent operations involving device objects. That proved to be too heavy-handed and we found a better way to achieve the goal, but before it happened, we had introduced the functions device_pm_schedule_removal() and destroy_suspended_device() to allow drivers to "safely" destroy a suspended device and we had adapted some drivers to use them. Now that these functions are no longer necessary, it seems reasonable to remove them and modify their users to use the normal device unregistration instead. Signed-off-by: Rafael J. Wysocki Acked-by: Pavel Machek Signed-off-by: Greg Kroah-Hartman

Misc: Add possibility to remove misc devices during suspend/resume

2008-02-05T17:44:23+00:00

Make it possible to unregister a misc device object in a safe way during a suspend/resume cycle. Signed-off-by: Rafael J. Wysocki Cc: Michael Buesch Cc: Pavel Machek Cc: "John W. Linville" Cc: Alan Stern Cc: Len Brown Cc: Greg KH Cc: Kay Sievers Cc: Richard Purdie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

KVM: Use own minor number

2007-05-03T07:52:22+00:00

Use the minor number (232) allocated to kvm by lanana. Signed-off-by: Avi Kivity

Driver core: change misc class_devices to be real devices

2006-12-01T22:51:59+00:00

This also ment that some of the misc drivers had to also be fixed up as they were assuming the device was a class_device. Signed-off-by: Greg Kroah-Hartman

[PATCH] devfs: Remove the miscdevice devfs_name field as it's no longer needed

2006-06-26T19:25:08+00:00

Also fixes all drivers that set this field. Signed-off-by: Greg Kroah-Hartman