HID: elecom: extend to fix the descriptor for DEFT trackballs

The ELECOM DEFT trackballs report only five buttons, when the device
actually has 8. Change the descriptor so that the HID driver can see all of
them.

For completeness and future reference, I included a side-by-side diff of
the part of the descriptor that is being edited.

Cc: Jiri Kosina <[e-mail]>
Cc: Benjamin Tissoires <[e-mail]>
Cc: Yuxuan Shui <[e-mail]>
Signed-off-by: Diego Elio Pettenò <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/Kconfig

···
 	 - Trio Linker Plus II
 
 config HID_ELECOM
-	tristate "ELECOM BM084 bluetooth mouse"
+	tristate "ELECOM HID devices"
 	depends on HID
 	---help---
-	Support for the ELECOM BM084 (bluetooth mouse).
+	Support for ELECOM devices:
+	  - BM084 Bluetooth Mouse
+	  - DEFT Trackball (Wired and wireless)
 
 config HID_ELO
 	tristate "ELO USB 4000/4500 touchscreen"

drivers/hid/hid-core.c

···
 	{ HID_USB_DEVICE(USB_VENDOR_ID_DREAM_CHEEKY, USB_DEVICE_ID_DREAM_CHEEKY_WN) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_DREAM_CHEEKY, USB_DEVICE_ID_DREAM_CHEEKY_FA) },
 	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_BM084) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT_WIRED) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT_WIRELESS) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_ELO, 0x0009) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_ELO, 0x0030) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_ELO, USB_DEVICE_ID_ELO_ACCUTOUCH_2216) },

drivers/hid/hid-elecom.c

···
 /*
- *  HID driver for Elecom BM084 (bluetooth mouse).
- *  Removes a non-existing horizontal wheel from
- *  the HID descriptor.
- *  (This module is based on "hid-ortek".)
- *
+ *  HID driver for ELECOM devices.
  *  Copyright (c) 2010 Richard Nauber <[e-mail]>
+ *  Copyright (c) 2016 Yuxuan Shui <[e-mail]>
+ *  Copyright (c) 2017 Diego Elio Pettenò <[e-mail]>
  */
 
 /*
···
 static __u8 *elecom_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 		unsigned int *rsize)
 {
-	if (*rsize >= 48 && rdesc[46] == 0x05 && rdesc[47] == 0x0c) {
-		hid_info(hdev, "Fixing up Elecom BM084 report descriptor\n");
-		rdesc[47] = 0x00;
+	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_DEFT_WIRED:
+	case USB_DEVICE_ID_ELECOM_DEFT_WIRELESS:
+		/* The DEFT trackball has eight buttons, but its descriptor only
+		 * reports five, disabling the three Fn buttons on the top of
+		 * the mouse.
+		 *
+		 * Apply the following diff to the descriptor:
+		 *
+		 * Collection (Physical),              Collection (Physical),
+		 *     Report ID (1),                      Report ID (1),
+		 *     Report Count (5),           ->      Report Count (8),
+		 *     Report Size (1),                    Report Size (1),
+		 *     Usage Page (Button),                Usage Page (Button),
+		 *     Usage Minimum (01h),                Usage Minimum (01h),
+		 *     Usage Maximum (05h),        ->      Usage Maximum (08h),
+		 *     Logical Minimum (0),                Logical Minimum (0),
+		 *     Logical Maximum (1),                Logical Maximum (1),
+		 *     Input (Variable),                   Input (Variable),
+		 *     Report Count (1),           ->      Report Count (0),
+		 *     Report Size (3),                    Report Size (3),
+		 *     Input (Constant),                   Input (Constant),
+		 *     Report Size (16),                   Report Size (16),
+		 *     Report Count (2),                   Report Count (2),
+		 *     Usage Page (Desktop),               Usage Page (Desktop),
+		 *     Usage (X),                          Usage (X),
+		 *     Usage (Y),                          Usage (Y),
+		 *     Logical Minimum (-32768),           Logical Minimum (-32768),
+		 *     Logical Maximum (32767),            Logical Maximum (32767),
+		 *     Input (Variable, Relative),         Input (Variable, Relative),
+		 * End Collection,                     End Collection,
+		 */
+		if (*rsize == 213 && rdesc[13] == 5 && rdesc[21] == 5) {
+			hid_info(hdev, "Fixing up Elecom DEFT Fn buttons\n");
+			rdesc[13] = 8; /* Button/Variable Report Count */
+			rdesc[21] = 8; /* Button/Variable Usage Maximum */
+			rdesc[29] = 0; /* Button/Constant Report Count */
+		}
+		break;
 	}
 	return rdesc;
 }
 
 static const struct hid_device_id elecom_devices[] = {
-	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_BM084)},
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_BM084) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT_WIRED) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT_WIRELESS) },
 	{ }
 };
 MODULE_DEVICE_TABLE(hid, elecom_devices);

drivers/hid/hid-ids.h

···
 
 #define USB_VENDOR_ID_ELECOM		0x056e
 #define USB_DEVICE_ID_ELECOM_BM084	0x0061
+#define USB_DEVICE_ID_ELECOM_DEFT_WIRED	0x00fe
+#define USB_DEVICE_ID_ELECOM_DEFT_WIRELESS	0x00ff
 
 #define USB_VENDOR_ID_DREAM_CHEEKY	0x1d34
 #define USB_DEVICE_ID_DREAM_CHEEKY_WN	0x0004