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SubjectRe: [PATCH] HID: elecom: fix the descriptor of the EX-G trackball
On Sat, Nov 18, 2017 at 10:27:26PM +0000, Tomasz Kramkowski wrote:
> I was going to do this just now actually but then I noticed that someone
> had beat me to the punch with the EX-G (I was already surprised when I
> found someone had patched the HUGE and DEFT).

Actually, I'll put my money where my mouth is.

Just some notes about the patch (maybe I talk too much, feel free to
skip the rambling):

I just tested this with the wired (I think there's a wireless variant
but I don't have it) ELECOM EX-G trackball mouse.

I've pulled in the previous relevant contributors to this file as CC.

I've dropped the big diff thing because I think that if you know the HID
spec you can probably understand most of what is happening from the
simple comment before the mouse_button_fixup function and the contents
of the function itself. Also, it would be a bit cumbersome to add a diff
for every potentially relevant device (I'm pretty sure the DEFT, HUGE
and EX-G aren't the only mice with this issue).

If removing the diff is a major problem then I propose just removing the
RHS and having just a visual representation of the relevant descriptor
fields.

At one point I thought of having a name parameter on mouse_button_fixup
which would vary the hid_info message depending on the device model but
then I decided that it was unnecessary complexity so I dropped it, but
if specifying EXACTLY which model of device the driver is fixing up is a
must then that's something that I can quickly add.

I've added a note about the aforementioned mystery FEATURE report to
hopefully prevent anyone else from going down that rabbit hole.

And finally, I didn't want to steal Yuxuan's thunder here so that's why
I didn't just send this in as a patch, but if he doesn't protest then
I'll just re-send it.

---
drivers/hid/Kconfig | 1 +
drivers/hid/hid-core.c | 1 +
drivers/hid/hid-elecom.c | 76 +++++++++++++++++++++++++-----------------------
drivers/hid/hid-ids.h | 1 +
4 files changed, 43 insertions(+), 36 deletions(-)

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 779c5ae47f36..772f695d4e8c 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -280,6 +280,7 @@ config HID_ELECOM
---help---
Support for ELECOM devices:
- BM084 Bluetooth Mouse
+ - EX-G Trackball
- DEFT Trackball (Wired and wireless)
- HUGE Trackball (Wired and wireless)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index f3fcb836a1f9..18912c045816 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2034,6 +2034,7 @@ static const struct hid_device_id hid_have_special_driver[] = {
#endif
#if IS_ENABLED(CONFIG_HID_ELECOM)
{ 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_DEFT_WIRED) },
{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_DEFT_WIRELESS) },
{ HID_USB_DEVICE(USB_VENDOR_ID_ELECOM, USB_DEVICE_ID_ELECOM_HUGE_WIRED) },
diff --git a/drivers/hid/hid-elecom.c b/drivers/hid/hid-elecom.c
index 54aeea57d209..d81cad44cc76 100644
--- a/drivers/hid/hid-elecom.c
+++ b/drivers/hid/hid-elecom.c
@@ -1,9 +1,15 @@
/*
- * HID driver for ELECOM devices.
+ * HID driver for ELECOM devices:
+ * - BM084 (bluetooth mouse)
+ * - EX-G (trackball)
+ * - DEFT (trackball, wired and wireless)
+ * - HUGE (trackball, wired and wireless)
+ *
* 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>
*/

/*
@@ -19,6 +25,34 @@

#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. 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)
{
@@ -31,45 +65,14 @@ static __u8 *elecom_report_fixup(struct hid_device *hdev, __u8 *rdesc,
rdesc[47] = 0x00;
}
break;
+ case USB_DEVICE_ID_ELECOM_EX_G_WIRED:
+ mouse_button_fixup(hdev, rdesc, rsize, 6);
+ break;
case USB_DEVICE_ID_ELECOM_DEFT_WIRED:
case USB_DEVICE_ID_ELECOM_DEFT_WIRELESS:
case USB_DEVICE_ID_ELECOM_HUGE_WIRED:
case USB_DEVICE_ID_ELECOM_HUGE_WIRELESS:
- /* The DEFT/HUGE 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/HUGE Fn buttons\n");
- rdesc[13] = 8; /* Button/Variable Report Count */
- rdesc[21] = 8; /* Button/Variable Usage Maximum */
- rdesc[29] = 0; /* Button/Constant Report Count */
- }
+ mouse_button_fixup(hdev, rdesc, rsize, 8);
break;
}
return rdesc;
@@ -77,6 +80,7 @@ static __u8 *elecom_report_fixup(struct hid_device *hdev, __u8 *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_EX_G_WIRED) },
{ 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_ELECOM, USB_DEVICE_ID_ELECOM_HUGE_WIRED) },
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 5da3d6256d25..d757c78e7e15 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -370,6 +370,7 @@

#define USB_VENDOR_ID_ELECOM 0x056e
#define USB_DEVICE_ID_ELECOM_BM084 0x0061
+#define USB_DEVICE_ID_ELECOM_EX_G_WIRED 0x00fb
#define USB_DEVICE_ID_ELECOM_DEFT_WIRED 0x00fe
#define USB_DEVICE_ID_ELECOM_DEFT_WIRELESS 0x00ff
#define USB_DEVICE_ID_ELECOM_HUGE_WIRED 0x010c
--
2.15.0
--
Tomasz Kramkowski | GPG: 40B037BA0A5B8680 | Web: https://the-tk.com/
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