+/*
+ * Allow user programs to claim ports on a hub. When a device is attached
+ * to one of these "claimed" ports, the program will "own" the device.
+ */
+static int find_port_owner(struct usb_device *hdev, unsigned port1,
+ void ***ppowner)
+{
+ if (hdev->state == USB_STATE_NOTATTACHED)
+ return -ENODEV;
+ if (port1 == 0 || port1 > hdev->maxchild)
+ return -EINVAL;
+
+ /* This assumes that devices not managed by the hub driver
+ * will always have maxchild equal to 0.
+ */
+ *ppowner = &(hdev_to_hub(hdev)->port_owners[port1 - 1]);
+ return 0;
+}
+
+/* In the following three functions, the caller must hold hdev's lock */
+int usb_hub_claim_port(struct usb_device *hdev, unsigned port1, void *owner)
+{
+ int rc;
+ void **powner;
+
+ rc = find_port_owner(hdev, port1, &powner);
+ if (rc)
+ return rc;
+ if (*powner)
+ return -EBUSY;
+ *powner = owner;
+ return rc;
+}
+
+int usb_hub_release_port(struct usb_device *hdev, unsigned port1, void *owner)
+{
+ int rc;
+ void **powner;
+
+ rc = find_port_owner(hdev, port1, &powner);
+ if (rc)
+ return rc;
+ if (*powner != owner)
+ return -ENOENT;
+ *powner = NULL;
+ return rc;
+}
+
+void usb_hub_release_all_ports(struct usb_device *hdev, void *owner)
+{
+ int n;
+ void **powner;
+
+ n = find_port_owner(hdev, 1, &powner);
+ if (n == 0) {
+ for (; n < hdev->maxchild; (++n, ++powner)) {
+ if (*powner == owner)
+ *powner = NULL;
+ }
+ }
+}
+
+/* The caller must hold udev's lock */
+bool usb_device_is_owned(struct usb_device *udev)
+{
+ struct usb_hub *hub;
+
+ if (udev->state == USB_STATE_NOTATTACHED || !udev->parent)
+ return false;
+ hub = hdev_to_hub(udev->parent);
+ return !!hub->port_owners[udev->portnum - 1];
+}
+