v4.19.13 snapshot.
diff --git a/drivers/hid/hid-elecom.c b/drivers/hid/hid-elecom.c
new file mode 100644
index 0000000..ae8e941
--- /dev/null
+++ b/drivers/hid/hid-elecom.c
@@ -0,0 +1,103 @@
+/*
+ * HID driver for ELECOM devices:
+ * - BM084 Bluetooth Mouse
+ * - EX-G Trackballs (M-XT3DRBK, M-XT3URBK, M-XT4DRBK)
+ * - DEFT Trackballs (M-DT1DRBK, M-DT1URBK, M-DT2DRBK, M-DT2URBK)
+ * - HUGE Trackballs (M-HT1DRBK, M-HT1URBK)
+ *
+ * Copyright (c) 2010 Richard Nauber <Richard.Nauber@gmail.com>
+ * Copyright (c) 2016 Yuxuan Shui <yshuiv7@gmail.com>
+ * Copyright (c) 2017 Diego Elio Pettenò <flameeyes@flameeyes.eu>
+ * Copyright (c) 2017 Alex Manoussakis <amanou@gnu.org>
+ * Copyright (c) 2017 Tomasz Kramkowski <tk@the-tk.com>
+ */
+
+/*
+ * 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/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+/*
+ * Certain ELECOM mice misreport their button count meaning that they only work
+ * correctly with the ELECOM mouse assistant software which is unavailable for
+ * Linux. A four extra INPUT reports and a FEATURE report are described by the
+ * report descriptor but it does not appear that these enable software to
+ * control what the extra buttons map to. The only simple and straightforward
+ * solution seems to involve fixing up the report descriptor.
+ *
+ * Report descriptor format:
+ * Positions 13, 15, 21 and 31 store the button bit count, button usage minimum,
+ * button usage maximum and padding bit count respectively.
+ */
+#define MOUSE_BUTTONS_MAX 8
+static void mouse_button_fixup(struct hid_device *hdev,
+ __u8 *rdesc, unsigned int rsize,
+ int nbuttons)
+{
+ if (rsize < 32 || rdesc[12] != 0x95 ||
+ rdesc[14] != 0x75 || rdesc[15] != 0x01 ||
+ rdesc[20] != 0x29 || rdesc[30] != 0x75)
+ return;
+ hid_info(hdev, "Fixing up Elecom mouse button count\n");
+ nbuttons = clamp(nbuttons, 0, MOUSE_BUTTONS_MAX);
+ rdesc[13] = nbuttons;
+ rdesc[21] = nbuttons;
+ rdesc[31] = MOUSE_BUTTONS_MAX - nbuttons;
+}
+
+static __u8 *elecom_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+ unsigned int *rsize)
+{
+ switch (hdev->product) {
+ case USB_DEVICE_ID_ELECOM_BM084:
+ /* The BM084 Bluetooth mouse includes a non-existing horizontal
+ * wheel in the HID descriptor. */
+ if (*rsize >= 48 && rdesc[46] == 0x05 && rdesc[47] == 0x0c) {
+ hid_info(hdev, "Fixing up Elecom BM084 report descriptor\n");
+ rdesc[47] = 0x00;
+ }
+ break;
+ case USB_DEVICE_ID_ELECOM_M_XT3URBK:
+ case USB_DEVICE_ID_ELECOM_M_XT3DRBK:
+ case USB_DEVICE_ID_ELECOM_M_XT4DRBK:
+ mouse_button_fixup(hdev, rdesc, *rsize, 6);
+ break;
+ case USB_DEVICE_ID_ELECOM_M_DT1URBK:
+ case USB_DEVICE_ID_ELECOM_M_DT1DRBK:
+ case USB_DEVICE_ID_ELECOM_M_HT1URBK:
+ case USB_DEVICE_ID_ELECOM_M_HT1DRBK:
+ mouse_button_fixup(hdev, rdesc, *rsize, 8);
+ break;
+ }
+ return rdesc;
+}
+
+static const struct hid_device_id elecom_devices[] = {
+ { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_BM084) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_XT3URBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_XT3DRBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_XT4DRBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_DT1URBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_DT1DRBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_HT1URBK) },
+ { HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_M_HT1DRBK) },
+ { }
+};
+MODULE_DEVICE_TABLE(hid, elecom_devices);
+
+static struct hid_driver elecom_driver = {
+ .name = "elecom",
+ .id_table = elecom_devices,
+ .report_fixup = elecom_report_fixup
+};
+module_hid_driver(elecom_driver);
+
+MODULE_LICENSE("GPL");