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Subject[PATCH] HID: elecom: rewrite report fixup for EX-G and future mice
Date
This patch rewrites the mouse report fixup used for the DEFT and HUGE
ELECOM trackballs in order to make it generic enough to fix other ELECOM
mice with similar issues. This patch also uses this new report fixup
function to fix the ELECOM EX-G trackball which has 6 physical buttons
and a similar issue to the other two mice.

ELECOM's track record has so far shown that they like to re-use the same
report descriptor for multiple different mice regardless of the number
of buttons the mouse has. This means that the missing buttons on
multiple mice can be fixed in one function without introducing phantom
buttons which would in turn cause the number of mouse buttons to be
misreported to userspace.

This patch drops the very verbose report descriptor "diff" comment for a
more abridged yet hopefully just as informative generic version.

Signed-off-by: Tomasz Kramkowski <tk@the-tk.com>
---
I've let this patch sit on the old thread [1] for two weeks now and
apart from the removal of the diff nobody has said anything about it so
I'm posting it as an actual patch now.

It includes a few small fixes that I missed when posting the old one and
this patch is based on the for-4.16/hid-quirks-cleanup/_base branch for
convenience. (Since the hid_have_special_driver array has moved to
hid-quirks.c now.)

Once again ccing all the relevant parties. I already explained my reason
for removing the long diff (unfortunately Diego's email about this got
dropped from the list as it was a HTML email) and why my replacement is
still as good.

This was tested with my EX-G but since I don't have a HUGE or DEFT I
have to rely on the fact that as far as I could tell the two report
descriptors are identical and as far as I can tell this change shouldn't
cause the fixup to work any differently for the other two mice which
were fixed. However, if one of the original authors of this fixup could
test with their mice I would very much appreciate the re-assurance.

P.S. Is that #define MOUSE_BUTTONS_MAX appropriate?

[1]: https://marc.info/?i=20171119002353.GA15931@gaia.local
---
drivers/hid/Kconfig | 1 +
drivers/hid/hid-elecom.c | 76 +++++++++++++++++++++++++-----------------------
drivers/hid/hid-ids.h | 1 +
drivers/hid/hid-quirks.c | 1 +
4 files changed, 43 insertions(+), 36 deletions(-)

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 9058dbc4dd6e..7b1a51c0f326 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 (Wired)
- DEFT Trackball (Wired and wireless)
- HUGE Trackball (Wired and wireless)

diff --git a/drivers/hid/hid-elecom.c b/drivers/hid/hid-elecom.c
index 54aeea57d209..b19361eaae3a 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 (Wired)
+ * - 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. 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)
{
@@ -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
diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
index 015e0c10248b..48054d2d6795 100644
--- a/drivers/hid/hid-quirks.c
+++ b/drivers/hid/hid-quirks.c
@@ -335,6 +335,7 @@ 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_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) },
--
2.15.1
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