[PATCH 0/1] hid: Add support for the Elecom DEFT trackball

[PATCH 0/1] hid: Add support for the Elecom DEFT trackball

[Yuxuan Shui]

Hi,

The Elecom DEFT is a trackball mouse, a picture can be found here [1].
As you can see, there're three Fn keys at the top of the mouse. These
keys doesn't work on current Linux kernel. Complains from several users
can be found on the internet [1][2].

The problem is in the HID report sent by the device, only 5 standard
buttons are reported. There's an additional 3*1 bit item without any
usage page in the report, which corresponds to the Fn buttons. This
patch remove that item, and change the number of standard buttons to 8.

[1]: http://xahlee.info/kbd/elecom_trackball.html
[2]: https://www.reddit.com/r/Trackballs/comments/4pu3cv/elecom_mdt2_fn_buttons_on_linux/

Regards,
Yuxuan Shui

[PATCH] hid: Add support for the Elecom DEFT trackball

[Yuxuan Shui]

The DEFT trackball has three non-standard buttons at the top which is
not supported by the hid-generic driver.

This patch add a driver that modifies the HID report, so those three
buttons can be supported like standard buttons.
---
 drivers/hid/Kconfig    |  6 ++++++
 drivers/hid/Makefile   |  1 +
 drivers/hid/hid-deft.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/hid/hid-ids.h  |  2 ++
 4 files changed, 61 insertions(+)
 create mode 100644 drivers/hid/hid-deft.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 5646ca4..9c3ee05 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -263,6 +263,12 @@ config HID_ELECOM
 	---help---
 	Support for the ELECOM BM084 (bluetooth mouse).
 
+config HID_ELECOM_DEFT
+	tristate "ELECOM DEFT trackball"
+	depends on HID
+	---help---
+	Support for the Fn keys found on ELECOM DEFT trackball.
+
 config HID_ELO
 	tristate "ELO USB 4000/4500 touchscreen"
 	depends on USB_HID
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index a2fb562..3cc582e 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_HID_CYPRESS)	+= hid-cypress.o
 obj-$(CONFIG_HID_DRAGONRISE)	+= hid-dr.o
 obj-$(CONFIG_HID_EMS_FF)	+= hid-emsff.o
 obj-$(CONFIG_HID_ELECOM)	+= hid-elecom.o
+obj-$(CONFIG_HID_ELECOM_DEFT)	+= hid-deft.o
 obj-$(CONFIG_HID_ELO)		+= hid-elo.o
 obj-$(CONFIG_HID_EZKEY)		+= hid-ezkey.o
 obj-$(CONFIG_HID_GEMBIRD)	+= hid-gembird.o
diff --git a/drivers/hid/hid-deft.c b/drivers/hid/hid-deft.c
new file mode 100644
index 0000000..4e2621d
--- /dev/null
+++ b/drivers/hid/hid-deft.c
@@ -0,0 +1,52 @@
+/*
+ *  HID driver for Elecom DEFT (trackball).
+ *  Extend the number of buttons to 8, and
+ *  remove a non-standard item in the HID
+ *  descriptor.
+ *  (This module is based on "hid-elecom".)
+ *
+ *  Copyright (c) 2016 Yuxuan Shui <yshuiv7@gmail.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"
+
+static __u8 *deft_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	if (*rsize >= 34 && rdesc[20] == 0x29 && rdesc[21] == 0x05) {
+		hid_info(hdev, "Fixing up Elecom DEFT report descriptor %x\n", rdesc[13]);
+		rdesc[21] = 0x08;
+		rdesc[13] = 0x08;
+
+		memmove(rdesc+28, rdesc+34, *rsize-34);
+		*rsize -= 6;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id deft_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT)},
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFTW)},
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, deft_devices);
+
+static struct hid_driver deft_driver = {
+	.name = "elecom-deft",
+	.id_table = deft_devices,
+	.report_fixup = deft_report_fixup,
+};
+module_hid_driver(deft_driver);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 3eec09a1..534ae73 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -332,6 +332,8 @@
 
 #define USB_VENDOR_ID_ELECOM		0x056e
 #define USB_DEVICE_ID_ELECOM_BM084	0x0061
+#define USB_DEVICE_ID_ELECOM_DEFT	0x00fe
+#define USB_DEVICE_ID_ELECOM_DEFTW	0x00ff
 
 #define USB_VENDOR_ID_DREAM_CHEEKY	0x1d34
 
-- 
2.9.0