USB: add API for userspace drivers to "claim" ports

This patch (as1258) implements a feature that users have been asking
for: It gives programs the ability to "claim" a port on a hub, via a
new usbfs ioctl.  A device plugged into a "claimed" port will not be
touched by the kernel beyond the immediate necessities of
initialization and enumeration.

In particular, when a device is plugged into a "claimed" port, the
kernel will not select and install a configuration.  And when a config
is installed by usbfs or sysfs, the kernel will not probe any drivers
for any of the interfaces.  (However the kernel will fetch various
string descriptors during enumeration.  One could argue that this
isn't really necessary, but the strings are exported in sysfs.)

The patch does not guarantee exclusive access to these devices; it is
still possible for more than one program to open the device file
concurrently.  Programs are responsible for coordinating access among
themselves.

A demonstration program showing how to use the new interface can be 
found in an attachment to

	http://marc.info/?l=linux-usb&m=124345857431452&w=2

The patch also makes a small simplification to the hub driver,
replacing a bunch of more-or-less useless variants of "out of memory"
with a single message.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/usbdevice_fs.h b/include/linux/usbdevice_fs.h
index 0044d9b4cb85..00ceebeb9e5c 100644
--- a/include/linux/usbdevice_fs.h
+++ b/include/linux/usbdevice_fs.h
@@ -175,4 +175,6 @@ struct usbdevfs_ioctl32 {
 #define USBDEVFS_CLEAR_HALT        _IOR('U', 21, unsigned int)
 #define USBDEVFS_DISCONNECT        _IO('U', 22)
 #define USBDEVFS_CONNECT           _IO('U', 23)
+#define USBDEVFS_CLAIM_PORT        _IOR('U', 24, unsigned int)
+#define USBDEVFS_RELEASE_PORT      _IOR('U', 25, unsigned int)
 #endif /* _LINUX_USBDEVICE_FS_H */