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, 7 insertions, 0 deletions

diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index c0e0ae2bb8e7..9a8b15e6377a 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -37,6 +37,13 @@ extern int usb_match_device(struct usb_device *dev,
 extern void usb_forced_unbind_intf(struct usb_interface *intf);
 extern void usb_rebind_intf(struct usb_interface *intf);
 
+extern int usb_hub_claim_port(struct usb_device *hdev, unsigned port,
+                void *owner);
+extern int usb_hub_release_port(struct usb_device *hdev, unsigned port,
+                void *owner);
+extern void usb_hub_release_all_ports(struct usb_device *hdev, void *owner);
+extern bool usb_device_is_owned(struct usb_device *udev);
+
 extern int  usb_hub_init(void);
 extern void usb_hub_cleanup(void);
 extern int usb_major_init(void);