HID: Add driver for Holtek gaming mouse 04d9:a067

This mouse is sold as Sharkoon Drakonia and Perixx MX-2000 and reports a
too high usage maximum and logical maximum. This driver fixes the report
descriptor so those values don't exceed HID_MAX_USAGES.

Signed-off-by: Christian Ohm <chr.ohm@gmx.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-holtek-mouse.c b/drivers/hid/hid-holtek-mouse.c
new file mode 100644
index 0000000..f32e29a
--- /dev/null
+++ b/drivers/hid/hid-holtek-mouse.c
@@ -0,0 +1,72 @@
+/*
+ * HID driver for Holtek gaming mice
+ * Copyright (c) 2013 Christian Ohm
+ * Heavily inspired by various other HID drivers that adjust the report
+ * descriptor.
+*/
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+
+#include "hid-ids.h"
+
+/*
+ * The report descriptor of some Holtek based gaming mice specifies an
+ * excessively large number of consumer usages (2^15), which is more than
+ * HID_MAX_USAGES. This prevents proper parsing of the report descriptor.
+ *
+ * This driver fixes the report descriptor for USB ID 04d9:a067, sold as
+ * Sharkoon Drakonia and Perixx MX-2000.
+ */
+
+static __u8 *holtek_mouse_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+
+	if (intf->cur_altsetting->desc.bInterfaceNumber == 1) {
+		/* Change usage maximum and logical maximum from 0x7fff to
+		 * 0x2fff, so they don't exceed HID_MAX_USAGES */
+		if (*rsize >= 122 && rdesc[115] == 0xff && rdesc[116] == 0x7f
+				&& rdesc[120] == 0xff && rdesc[121] == 0x7f) {
+			hid_info(hdev, "Fixing up report descriptor\n");
+			rdesc[116] = rdesc[121] = 0x2f;
+		}
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id holtek_mouse_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A067) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, holtek_mouse_devices);
+
+static struct hid_driver holtek_mouse_driver = {
+	.name = "holtek_mouse",
+	.id_table = holtek_mouse_devices,
+	.report_fixup = holtek_mouse_report_fixup,
+};
+
+static int __init holtek_mouse_init(void)
+{
+	return hid_register_driver(&holtek_mouse_driver);
+}
+
+static void __exit holtek_mouse_exit(void)
+{
+	hid_unregister_driver(&holtek_mouse_driver);
+}
+
+module_exit(holtek_mouse_exit);
+module_init(holtek_mouse_init);
+MODULE_LICENSE("GPL");