HID: elecom: rewrite report fixup for EX-G and future mice

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 <[email protected]> Signed-off-by: Jiri Kosina <[email protected]>
penberg · Jan 23, 2018 · ac58eec · ac58eec
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commit ac58eec
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Showing 4 changed files with 47 additions and 36 deletions.
diff --git 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 and wireless)
 	  - DEFT Trackball (Wired and wireless)
 	  - HUGE Trackball (Wired and wireless)
 

diff --git 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 and wireless)
+ *  - DEFT Trackball (Wired and wireless)
+ *  - HUGE Trackball (Wired and wireless)
+ *
  *  Copyright (c) 2010 Richard Nauber <[email protected]>
  *  Copyright (c) 2016 Yuxuan Shui <[email protected]>
  *  Copyright (c) 2017 Diego Elio Pettenò <[email protected]>
  *  Copyright (c) 2017 Alex Manoussakis <[email protected]>
+ *  Copyright (c) 2017 Tomasz Kramkowski <[email protected]>
  */
 
 /*
@@ -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)
 {
@@ -31,52 +65,24 @@ static __u8 *elecom_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 			rdesc[47] = 0x00;
 		}
 		break;
+	case USB_DEVICE_ID_ELECOM_EX_G_WIRED:
+	case USB_DEVICE_ID_ELECOM_EX_G_WIRELESS:
+		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;
 }
 
 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_EX_G_WIRELESS) },
 	{ 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
@@ -370,6 +370,8 @@
 
 #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_EX_G_WIRELESS	0x00fc
 #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
@@ -335,6 +335,8 @@ 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_EX_G_WIRELESS) },
 	{ 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) },