Re: [PATCH] configfs, a filesystem for userspace-driven kernel object configuration

[Matt Mackall]

On Sun, Apr 03, 2005 at 12:57:28PM -0700, Joel Becker wrote:
> Folks,
> 	I humbly submit configfs.  With configfs, a configfs
> config_item is created via an explicit userspace operation: mkdir(2).
> It is destroyed via rmdir(2).  The attributes appear at mkdir(2) time,
> and can be read or modified via read(2) and write(2).  readdir(3)
> queries the list of items and/or attributes.
> 	The lifetime of the filesystem representation is completely
> driven by userspace.  The lifetime of the objects themselves are managed
> by a kref, but at rmdir(2) time they disappear from the filesystem.
> 	configfs is not intended to replace sysfs or procfs, merely to
> coexist with them.
> 	An interface in /proc where the API is: 
> 
> 	# echo "create foo 1 3 0x00013" > /proc/mythingy
> 
> or an ioctl(2) interface where the API is:
> 
> 	struct mythingy_create {
> 		char *name;
> 		int index;
> 		int count;
> 		unsigned long address;
> 	}
> 
> 	do_create {
> 		mythingy_create = {"foo", 1, 3, 0x0013};
> 		return ioctl(fd, MYTHINGY_CREATE, &mythingy_create);
> 	}
> 
> becomes this in configfs:
> 
> 	# cd /config/mythingy
> 	# mkdir foo
> 	# echo 1 > foo/index
> 	# echo 3 > foo/count
> 	# echo 0x00013 > foo/address
> 
> 	Instead of a binary blob that's passed around or a cryptic
> string that has to be formatted just so, configfs provides an interface
> that's completely scriptable and navigable.

How does the kernel know when to actually create the object?

-- 
Mathematics is the supreme nostalgia of our time.
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