+static void hid_scan_usage(struct hid_device *hid, u32 usage)
+{
+ if (usage == HID_DG_CONTACTID)
+ hid->group = HID_GROUP_MULTITOUCH;
+}
+
+/*
+ * Scan a report descriptor before the device is added to the bus.
+ * Sets device groups and other properties that determine what driver
+ * to load.
+ */
+static int hid_scan_report(struct hid_device *hid)
+{
+ unsigned int page = 0, delim = 0;
+ __u8 *start = hid->dev_rdesc;
+ __u8 *end = start + hid->dev_rsize;
+ unsigned int u, u_min = 0, u_max = 0;
+ struct hid_item item;
+
+ hid->group = HID_GROUP_GENERIC;
+ while ((start = fetch_item(start, end, &item)) != NULL) {
+ if (item.format != HID_ITEM_FORMAT_SHORT)
+ return -EINVAL;
+ if (item.type == HID_ITEM_TYPE_GLOBAL) {
+ if (item.tag == HID_GLOBAL_ITEM_TAG_USAGE_PAGE)
+ page = item_udata(&item) << 16;
+ } else if (item.type == HID_ITEM_TYPE_LOCAL) {
+ if (delim > 1)
+ break;
+ u = item_udata(&item);
+ if (item.size <= 2)
+ u += page;
+ switch (item.tag) {
+ case HID_LOCAL_ITEM_TAG_DELIMITER:
+ delim += !!u;
+ break;
+ case HID_LOCAL_ITEM_TAG_USAGE:
+ hid_scan_usage(hid, u);
+ break;
+ case HID_LOCAL_ITEM_TAG_USAGE_MINIMUM:
+ u_min = u;
+ break;
+ case HID_LOCAL_ITEM_TAG_USAGE_MAXIMUM:
+ u_max = u;
+ for (u = u_min; u <= u_max; u++)
+ hid_scan_usage(hid, u);
+ break;
+ }
+ }
+ }
+
+ return 0;
+}
+