Merge branch 'for-4.20/logitech-highres' into for-linus

High-resolution support for hid-logitech

Documentation/input/event-codes.rst

@@ -190,7 +190,16 @@ A few EV_REL codes have special meanings:
 * REL_WHEEL, REL_HWHEEL:
 
   - These codes are used for vertical and horizontal scroll wheels,
-    respectively.
+    respectively. The value is the number of "notches" moved on the wheel, the
+    physical size of which varies by device. For high-resolution wheels (which
+    report multiple events for each notch of movement, or do not have notches)
+    this may be an approximation based on the high-resolution scroll events.
+
+* REL_WHEEL_HI_RES:
+
+  - If a vertical scroll wheel supports high-resolution scrolling, this code
+    will be emitted in addition to REL_WHEEL. The value is the (approximate)
+    distance travelled by the user's finger, in microns.
 
 EV_ABS
 ------

drivers/hid/hid-input.c

@@ -1838,3 +1838,48 @@ void hidinput_disconnect(struct hid_device *hid)
 }
 EXPORT_SYMBOL_GPL(hidinput_disconnect);
 
+/**
+ * hid_scroll_counter_handle_scroll() - Send high- and low-resolution scroll
+ *                                      events given a high-resolution wheel
+ *                                      movement.
+ * @counter: a hid_scroll_counter struct describing the wheel.
+ * @hi_res_value: the movement of the wheel, in the mouse's high-resolution
+ *                units.
+ *
+ * Given a high-resolution movement, this function converts the movement into
+ * microns and emits high-resolution scroll events for the input device. It also
+ * uses the multiplier from &struct hid_scroll_counter to emit low-resolution
+ * scroll events when appropriate for backwards-compatibility with userspace
+ * input libraries.
+ */
+void hid_scroll_counter_handle_scroll(struct hid_scroll_counter *counter,
+				      int hi_res_value)
+{
+	int low_res_scroll_amount;
+	/* Some wheels will rest 7/8ths of a notch from the previous notch
+	 * after slow movement, so we want the threshold for low-res events to
+	 * be in the middle of the notches (e.g. after 4/8ths) as opposed to on
+	 * the notches themselves (8/8ths).
+	 */
+	int threshold = counter->resolution_multiplier / 2;
+
+	input_report_rel(counter->dev, REL_WHEEL_HI_RES,
+			 hi_res_value * counter->microns_per_hi_res_unit);
+
+	counter->remainder += hi_res_value;
+	if (abs(counter->remainder) >= threshold) {
+		/* Add (or subtract) 1 because we want to trigger when the wheel
+		 * is half-way to the next notch (i.e. scroll 1 notch after a
+		 * 1/2 notch movement, 2 notches after a 1 1/2 notch movement,
+		 * etc.).
+		 */
+		low_res_scroll_amount =
+			counter->remainder / counter->resolution_multiplier
+			+ (hi_res_value > 0 ? 1 : -1);
+		input_report_rel(counter->dev, REL_WHEEL,
+				 low_res_scroll_amount);
+		counter->remainder -=
+			low_res_scroll_amount * counter->resolution_multiplier;
+	}
+}
+EXPORT_SYMBOL_GPL(hid_scroll_counter_handle_scroll);

drivers/hid/hid-logitech-hidpp.c

@@ -64,6 +64,14 @@ MODULE_PARM_DESC(disable_tap_to_click,
 #define HIDPP_QUIRK_NO_HIDINPUT			BIT(23)
 #define HIDPP_QUIRK_FORCE_OUTPUT_REPORTS	BIT(24)
 #define HIDPP_QUIRK_UNIFYING			BIT(25)
+#define HIDPP_QUIRK_HI_RES_SCROLL_1P0		BIT(26)
+#define HIDPP_QUIRK_HI_RES_SCROLL_X2120		BIT(27)
+#define HIDPP_QUIRK_HI_RES_SCROLL_X2121		BIT(28)
+
+/* Convenience constant to check for any high-res support. */
+#define HIDPP_QUIRK_HI_RES_SCROLL	(HIDPP_QUIRK_HI_RES_SCROLL_1P0 | \
+					 HIDPP_QUIRK_HI_RES_SCROLL_X2120 | \
+					 HIDPP_QUIRK_HI_RES_SCROLL_X2121)
 
 #define HIDPP_QUIRK_DELAYED_INIT		HIDPP_QUIRK_NO_HIDINPUT
 
@@ -149,6 +157,7 @@ struct hidpp_device {
 	unsigned long capabilities;
 
 	struct hidpp_battery battery;
+	struct hid_scroll_counter vertical_wheel_counter;
 };
 
 /* HID++ 1.0 error codes */
@@ -400,9 +409,15 @@ static void hidpp_prefix_name(char **name, int name_length)
 #define HIDPP_SET_LONG_REGISTER				0x82
 #define HIDPP_GET_LONG_REGISTER				0x83
 
-#define HIDPP_REG_GENERAL				0x00
-
-static int hidpp10_enable_battery_reporting(struct hidpp_device *hidpp_dev)
+/**
+ * hidpp10_set_register_bit() - Sets a single bit in a HID++ 1.0 register.
+ * @hidpp_dev: the device to set the register on.
+ * @register_address: the address of the register to modify.
+ * @byte: the byte of the register to modify. Should be less than 3.
+ * Return: 0 if successful, otherwise a negative error code.
+ */
+static int hidpp10_set_register_bit(struct hidpp_device *hidpp_dev,
+	u8 register_address, u8 byte, u8 bit)
 {
 	struct hidpp_report response;
 	int ret;
@@ -411,23 +426,38 @@ static int hidpp10_enable_battery_reporting(struct hidpp_device *hidpp_dev)
 	ret = hidpp_send_rap_command_sync(hidpp_dev,
 					  REPORT_ID_HIDPP_SHORT,
 					  HIDPP_GET_REGISTER,
-					HIDPP_REG_GENERAL,
+					  register_address,
 					  NULL, 0, &response);
 	if (ret)
 		return ret;
 
 	memcpy(params, response.rap.params, 3);
 
-	/* Set the battery bit */
-	params[0] |= BIT(4);
+	params[byte] |= BIT(bit);
 
 	return hidpp_send_rap_command_sync(hidpp_dev,
 					   REPORT_ID_HIDPP_SHORT,
 					   HIDPP_SET_REGISTER,
-					HIDPP_REG_GENERAL,
+					   register_address,
 					   params, 3, &response);
 }
 
+
+#define HIDPP_REG_GENERAL				0x00
+
+static int hidpp10_enable_battery_reporting(struct hidpp_device *hidpp_dev)
+{
+	return hidpp10_set_register_bit(hidpp_dev, HIDPP_REG_GENERAL, 0, 4);
+}
+
+#define HIDPP_REG_FEATURES				0x01
+
+/* On HID++ 1.0 devices, high-res scroll was called "scrolling acceleration". */
+static int hidpp10_enable_scrolling_acceleration(struct hidpp_device *hidpp_dev)
+{
+	return hidpp10_set_register_bit(hidpp_dev, HIDPP_REG_FEATURES, 0, 6);
+}
+
 #define HIDPP_REG_BATTERY_STATUS			0x07
 
 static int hidpp10_battery_status_map_level(u8 param)
@@ -1136,6 +1166,100 @@ static int hidpp_battery_get_property(struct power_supply *psy,
 	return ret;
 }
 
+/* -------------------------------------------------------------------------- */
+/* 0x2120: Hi-resolution scrolling                                            */
+/* -------------------------------------------------------------------------- */
+
+#define HIDPP_PAGE_HI_RESOLUTION_SCROLLING			0x2120
+
+#define CMD_HI_RESOLUTION_SCROLLING_SET_HIGHRES_SCROLLING_MODE	0x10
+
+static int hidpp_hrs_set_highres_scrolling_mode(struct hidpp_device *hidpp,
+	bool enabled, u8 *multiplier)
+{
+	u8 feature_index;
+	u8 feature_type;
+	int ret;
+	u8 params[1];
+	struct hidpp_report response;
+
+	ret = hidpp_root_get_feature(hidpp,
+				     HIDPP_PAGE_HI_RESOLUTION_SCROLLING,
+				     &feature_index,
+				     &feature_type);
+	if (ret)
+		return ret;
+
+	params[0] = enabled ? BIT(0) : 0;
+	ret = hidpp_send_fap_command_sync(hidpp, feature_index,
+					  CMD_HI_RESOLUTION_SCROLLING_SET_HIGHRES_SCROLLING_MODE,
+					  params, sizeof(params), &response);
+	if (ret)
+		return ret;
+	*multiplier = response.fap.params[1];
+	return 0;
+}
+
+/* -------------------------------------------------------------------------- */
+/* 0x2121: HiRes Wheel                                                        */
+/* -------------------------------------------------------------------------- */
+
+#define HIDPP_PAGE_HIRES_WHEEL		0x2121
+
+#define CMD_HIRES_WHEEL_GET_WHEEL_CAPABILITY	0x00
+#define CMD_HIRES_WHEEL_SET_WHEEL_MODE		0x20
+
+static int hidpp_hrw_get_wheel_capability(struct hidpp_device *hidpp,
+	u8 *multiplier)
+{
+	u8 feature_index;
+	u8 feature_type;
+	int ret;
+	struct hidpp_report response;
+
+	ret = hidpp_root_get_feature(hidpp, HIDPP_PAGE_HIRES_WHEEL,
+				     &feature_index, &feature_type);
+	if (ret)
+		goto return_default;
+
+	ret = hidpp_send_fap_command_sync(hidpp, feature_index,
+					  CMD_HIRES_WHEEL_GET_WHEEL_CAPABILITY,
+					  NULL, 0, &response);
+	if (ret)
+		goto return_default;
+
+	*multiplier = response.fap.params[0];
+	return 0;
+return_default:
+	hid_warn(hidpp->hid_dev,
+		 "Couldn't get wheel multiplier (error %d), assuming %d.\n",
+		 ret, *multiplier);
+	return ret;
+}
+
+static int hidpp_hrw_set_wheel_mode(struct hidpp_device *hidpp, bool invert,
+	bool high_resolution, bool use_hidpp)
+{
+	u8 feature_index;
+	u8 feature_type;
+	int ret;
+	u8 params[1];
+	struct hidpp_report response;
+
+	ret = hidpp_root_get_feature(hidpp, HIDPP_PAGE_HIRES_WHEEL,
+				     &feature_index, &feature_type);
+	if (ret)
+		return ret;
+
+	params[0] = (invert          ? BIT(2) : 0) |
+		    (high_resolution ? BIT(1) : 0) |
+		    (use_hidpp       ? BIT(0) : 0);
+
+	return hidpp_send_fap_command_sync(hidpp, feature_index,
+					   CMD_HIRES_WHEEL_SET_WHEEL_MODE,
+					   params, sizeof(params), &response);
+}
+
 /* -------------------------------------------------------------------------- */
 /* 0x4301: Solar Keyboard                                                     */
 /* -------------------------------------------------------------------------- */
@@ -2399,7 +2523,8 @@ static int m560_raw_event(struct hid_device *hdev, u8 *data, int size)
 		input_report_rel(mydata->input, REL_Y, v);
 
 		v = hid_snto32(data[6], 8);
-		input_report_rel(mydata->input, REL_WHEEL, v);
+		hid_scroll_counter_handle_scroll(
+				&hidpp->vertical_wheel_counter, v);
 
 		input_sync(mydata->input);
 	}
@@ -2527,6 +2652,72 @@ static int g920_get_config(struct hidpp_device *hidpp)
 	return 0;
 }
 
+/* -------------------------------------------------------------------------- */
+/* High-resolution scroll wheels                                              */
+/* -------------------------------------------------------------------------- */
+
+/**
+ * struct hi_res_scroll_info - Stores info on a device's high-res scroll wheel.
+ * @product_id: the HID product ID of the device being described.
+ * @microns_per_hi_res_unit: the distance moved by the user's finger for each
+ *                         high-resolution unit reported by the device, in
+ *                         256ths of a millimetre.
+ */
+struct hi_res_scroll_info {
+	__u32 product_id;
+	int microns_per_hi_res_unit;
+};
+
+static struct hi_res_scroll_info hi_res_scroll_devices[] = {
+	{ /* Anywhere MX */
+	  .product_id = 0x1017, .microns_per_hi_res_unit = 445 },
+	{ /* Performance MX */
+	  .product_id = 0x101a, .microns_per_hi_res_unit = 406 },
+	{ /* M560 */
+	  .product_id = 0x402d, .microns_per_hi_res_unit = 435 },
+	{ /* MX Master 2S */
+	  .product_id = 0x4069, .microns_per_hi_res_unit = 406 },
+};
+
+static int hi_res_scroll_look_up_microns(__u32 product_id)
+{
+	int i;
+	int num_devices = sizeof(hi_res_scroll_devices)
+			  / sizeof(hi_res_scroll_devices[0]);
+	for (i = 0; i < num_devices; i++) {
+		if (hi_res_scroll_devices[i].product_id == product_id)
+			return hi_res_scroll_devices[i].microns_per_hi_res_unit;
+	}
+	/* We don't have a value for this device, so use a sensible default. */
+	return 406;
+}
+
+static int hi_res_scroll_enable(struct hidpp_device *hidpp)
+{
+	int ret;
+	u8 multiplier = 8;
+
+	if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL_X2121) {
+		ret = hidpp_hrw_set_wheel_mode(hidpp, false, true, false);
+		hidpp_hrw_get_wheel_capability(hidpp, &multiplier);
+	} else if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL_X2120) {
+		ret = hidpp_hrs_set_highres_scrolling_mode(hidpp, true,
+							   &multiplier);
+	} else /* if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL_1P0) */
+		ret = hidpp10_enable_scrolling_acceleration(hidpp);
+
+	if (ret)
+		return ret;
+
+	hidpp->vertical_wheel_counter.resolution_multiplier = multiplier;
+	hidpp->vertical_wheel_counter.microns_per_hi_res_unit =
+		hi_res_scroll_look_up_microns(hidpp->hid_dev->product);
+	hid_info(hidpp->hid_dev, "multiplier = %d, microns = %d\n",
+		 multiplier,
+		 hidpp->vertical_wheel_counter.microns_per_hi_res_unit);
+	return 0;
+}
+
 /* -------------------------------------------------------------------------- */
 /* Generic HID++ devices                                                      */
 /* -------------------------------------------------------------------------- */
@@ -2572,6 +2763,11 @@ static void hidpp_populate_input(struct hidpp_device *hidpp,
 		wtp_populate_input(hidpp, input, origin_is_hid_core);
 	else if (hidpp->quirks & HIDPP_QUIRK_CLASS_M560)
 		m560_populate_input(hidpp, input, origin_is_hid_core);
+
+	if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL) {
+		input_set_capability(input, EV_REL, REL_WHEEL_HI_RES);
+		hidpp->vertical_wheel_counter.dev = input;
+	}
 }
 
 static int hidpp_input_configured(struct hid_device *hdev,
@@ -2690,6 +2886,27 @@ static int hidpp_raw_event(struct hid_device *hdev, struct hid_report *report,
 	return 0;
 }
 
+static int hidpp_event(struct hid_device *hdev, struct hid_field *field,
+	struct hid_usage *usage, __s32 value)
+{
+	/* This function will only be called for scroll events, due to the
+	 * restriction imposed in hidpp_usages.
+	 */
+	struct hidpp_device *hidpp = hid_get_drvdata(hdev);
+	struct hid_scroll_counter *counter = &hidpp->vertical_wheel_counter;
+	/* A scroll event may occur before the multiplier has been retrieved or
+	 * the input device set, or high-res scroll enabling may fail. In such
+	 * cases we must return early (falling back to default behaviour) to
+	 * avoid a crash in hid_scroll_counter_handle_scroll.
+	 */
+	if (!(hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL) || value == 0
+	    || counter->dev == NULL || counter->resolution_multiplier == 0)
+		return 0;
+
+	hid_scroll_counter_handle_scroll(counter, value);
+	return 1;
+}
+
 static int hidpp_initialize_battery(struct hidpp_device *hidpp)
 {
 	static atomic_t battery_no = ATOMIC_INIT(0);
@@ -2901,6 +3118,9 @@ static void hidpp_connect_event(struct hidpp_device *hidpp)
 	if (hidpp->battery.ps)
 		power_supply_changed(hidpp->battery.ps);
 
+	if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL)
+		hi_res_scroll_enable(hidpp);
+
 	if (!(hidpp->quirks & HIDPP_QUIRK_NO_HIDINPUT) || hidpp->delayed_input)
 		/* if the input nodes are already created, we can stop now */
 		return;
@@ -3086,35 +3306,63 @@ static void hidpp_remove(struct hid_device *hdev)
 	mutex_destroy(&hidpp->send_mutex);
 }
 
+#define LDJ_DEVICE(product) \
+	HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE, \
+		   USB_VENDOR_ID_LOGITECH, (product))
+
 static const struct hid_device_id hidpp_devices[] = {
 	{ /* wireless touchpad */
-	  HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, 0x4011),
+	  LDJ_DEVICE(0x4011),
 	  .driver_data = HIDPP_QUIRK_CLASS_WTP | HIDPP_QUIRK_DELAYED_INIT |
 			 HIDPP_QUIRK_WTP_PHYSICAL_BUTTONS },
 	{ /* wireless touchpad T650 */
-	  HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, 0x4101),
+	  LDJ_DEVICE(0x4101),
 	  .driver_data = HIDPP_QUIRK_CLASS_WTP | HIDPP_QUIRK_DELAYED_INIT },
 	{ /* wireless touchpad T651 */
 	  HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
 		USB_DEVICE_ID_LOGITECH_T651),
 	  .driver_data = HIDPP_QUIRK_CLASS_WTP },
+	{ /* Mouse Logitech Anywhere MX */
+	  LDJ_DEVICE(0x1017), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_1P0 },
+	{ /* Mouse Logitech Cube */
+	  LDJ_DEVICE(0x4010), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2120 },
+	{ /* Mouse Logitech M335 */
+	  LDJ_DEVICE(0x4050), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech M515 */
+	  LDJ_DEVICE(0x4007), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2120 },
 	{ /* Mouse logitech M560 */
-	  HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, 0x402d),
-	  .driver_data = HIDPP_QUIRK_DELAYED_INIT | HIDPP_QUIRK_CLASS_M560 },
+	  LDJ_DEVICE(0x402d),
+	  .driver_data = HIDPP_QUIRK_DELAYED_INIT | HIDPP_QUIRK_CLASS_M560
+		| HIDPP_QUIRK_HI_RES_SCROLL_X2120 },
+	{ /* Mouse Logitech M705 (firmware RQM17) */
+	  LDJ_DEVICE(0x101b), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_1P0 },
+	{ /* Mouse Logitech M705 (firmware RQM67) */
+	  LDJ_DEVICE(0x406d), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech M720 */
+	  LDJ_DEVICE(0x405e), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Anywhere 2 */
+	  LDJ_DEVICE(0x404a), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ LDJ_DEVICE(0xb013), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ LDJ_DEVICE(0xb018), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ LDJ_DEVICE(0xb01f), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Anywhere 2S */
+	  LDJ_DEVICE(0x406a), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Master */
+	  LDJ_DEVICE(0x4041), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ LDJ_DEVICE(0x4060), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ LDJ_DEVICE(0x4071), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Master 2S */
+	  LDJ_DEVICE(0x4069), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech Performance MX */
+	  LDJ_DEVICE(0x101a), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_1P0 },
 	{ /* Keyboard logitech K400 */
-	  HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, 0x4024),
+	  LDJ_DEVICE(0x4024),
 	  .driver_data = HIDPP_QUIRK_CLASS_K400 },
 	{ /* Solar Keyboard Logitech K750 */
-	  HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, 0x4002),
+	  LDJ_DEVICE(0x4002),
 	  .driver_data = HIDPP_QUIRK_CLASS_K750 },
 
-	{ HID_DEVICE(BUS_USB, HID_GROUP_LOGITECH_DJ_DEVICE,
-		USB_VENDOR_ID_LOGITECH, HID_ANY_ID)},
+	{ LDJ_DEVICE(HID_ANY_ID) },
 
 	{ HID_USB_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_G920_WHEEL),
 		.driver_data = HIDPP_QUIRK_CLASS_G920 | HIDPP_QUIRK_FORCE_OUTPUT_REPORTS},
@@ -3123,12 +3371,19 @@ static const struct hid_device_id hidpp_devices[] = {
 
 MODULE_DEVICE_TABLE(hid, hidpp_devices);
 
+static const struct hid_usage_id hidpp_usages[] = {
+	{ HID_GD_WHEEL, EV_REL, REL_WHEEL },
+	{ HID_ANY_ID - 1, HID_ANY_ID - 1, HID_ANY_ID - 1}
+};
+
 static struct hid_driver hidpp_driver = {
 	.name = "logitech-hidpp-device",
 	.id_table = hidpp_devices,
 	.probe = hidpp_probe,
 	.remove = hidpp_remove,
 	.raw_event = hidpp_raw_event,
+	.usage_table = hidpp_usages,
+	.event = hidpp_event,
 	.input_configured = hidpp_input_configured,
 	.input_mapping = hidpp_input_mapping,
 	.input_mapped = hidpp_input_mapped,

include/linux/hid.h

@@ -1139,6 +1139,34 @@ static inline u32 hid_report_len(struct hid_report *report)
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
 		int interrupt);
 
+
+/**
+ * struct hid_scroll_counter - Utility class for processing high-resolution
+ *                             scroll events.
+ * @dev: the input device for which events should be reported.
+ * @microns_per_hi_res_unit: the amount moved by the user's finger for each
+ *                           high-resolution unit reported by the mouse, in
+ *                           microns.
+ * @resolution_multiplier: the wheel's resolution in high-resolution mode as a
+ *                         multiple of its lower resolution. For example, if
+ *                         moving the wheel by one "notch" would result in a
+ *                         value of 1 in low-resolution mode but 8 in
+ *                         high-resolution, the multiplier is 8.
+ * @remainder: counts the number of high-resolution units moved since the last
+ *             low-resolution event (REL_WHEEL or REL_HWHEEL) was sent. Should
+ *             only be used by class methods.
+ */
+struct hid_scroll_counter {
+	struct input_dev *dev;
+	int microns_per_hi_res_unit;
+	int resolution_multiplier;
+
+	int remainder;
+};
+
+void hid_scroll_counter_handle_scroll(struct hid_scroll_counter *counter,
+				      int hi_res_value);
+
 /* HID quirks API */
 unsigned long hid_lookup_quirk(const struct hid_device *hdev);
 int hid_quirks_init(char **quirks_param, __u16 bus, int count);

include/uapi/linux/input-event-codes.h

@@ -708,6 +708,15 @@
 #define REL_DIAL		0x07
 #define REL_WHEEL		0x08
 #define REL_MISC		0x09
+/*
+ * 0x0a is reserved and should not be used in input drivers.
+ * It was used by HID as REL_MISC+1 and userspace needs to detect if
+ * the next REL_* event is correct or is just REL_MISC + n.
+ * We define here REL_RESERVED so userspace can rely on it and detect
+ * the situation described above.
+ */
+#define REL_RESERVED		0x0a
+#define REL_WHEEL_HI_RES	0x0b
 #define REL_MAX			0x0f
 #define REL_CNT			(REL_MAX+1)
 
@@ -744,6 +753,15 @@
 
 #define ABS_MISC		0x28
 
+/*
+ * 0x2e is reserved and should not be used in input drivers.
+ * It was used by HID as ABS_MISC+6 and userspace needs to detect if
+ * the next ABS_* event is correct or is just ABS_MISC + n.
+ * We define here ABS_RESERVED so userspace can rely on it and detect
+ * the situation described above.
+ */
+#define ABS_RESERVED		0x2e
+
 #define ABS_MT_SLOT		0x2f	/* MT slot being modified */
 #define ABS_MT_TOUCH_MAJOR	0x30	/* Major axis of touching ellipse */
 #define ABS_MT_TOUCH_MINOR	0x31	/* Minor axis (omit if circular) */