[PATCH 0/3] Add support for high-resolution scrolling on Logitech mice

STALE2908d

Revision v1 of 2 in this series.

10 messages, 5 authors, 2018-08-28 · open the first message on its own page

[PATCH 0/3] Add support for high-resolution scrolling on Logitech mice

From: Harry Cutts <hidden>
Date: 2018-08-23 18:31:13

Hi everyone,

This set of patches adds support for high-resolution scroll wheels on
Logitech mice. See the linux-input "Reporting high-resolution scroll
events" thread [0] for previous discussion of the evdev changes. I would
love to hear your feedback.

Thanks,

Harry Cutts
Chrome OS Touch/Input team

[0]: https://www.spinics.net/lists/linux-input/msg57380.html



Harry Cutts (3):
  Add the `REL_WHEEL_HI_RES` event code
  Create a utility class for counting scroll events
  Enable high-resolution scrolling on Logitech mice

 Documentation/input/event-codes.rst    |  11 +-
 drivers/hid/hid-ids.h                  |  15 ++
 drivers/hid/hid-input.c                |  44 ++++
 drivers/hid/hid-logitech-hidpp.c       | 341 +++++++++++++++++++++++--
 drivers/hid/hid-quirks.c               |  11 +
 include/linux/hid.h                    |  28 ++
 include/uapi/linux/input-event-codes.h |   1 +
 7 files changed, 423 insertions(+), 28 deletions(-)

-- 
2.18.0.1017.ga543ac7ca45-goog

[PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Harry Cutts <hidden>
Date: 2018-08-23 18:31:38

This event code represents scroll reports from high-resolution wheels,
and will be used by future patches in this series. See the linux-input
"Reporting high-resolution scroll events" thread [0] for more details.

[0]: https://www.spinics.net/lists/linux-input/msg57380.html

Signed-off-by: Harry Cutts <redacted>
---

 Documentation/input/event-codes.rst    | 11 ++++++++++-
 include/uapi/linux/input-event-codes.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/Documentation/input/event-codes.rst b/Documentation/input/event-codes.rst
index a8c0873beb95..df024cb82829 100644
--- a/Documentation/input/event-codes.rst
+++ b/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 256ths of a millimeter.
 
 EV_ABS
 ------
diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h
index 53fbae27b280..dad8d3890a3a 100644
--- a/include/uapi/linux/input-event-codes.h
+++ b/include/uapi/linux/input-event-codes.h
@@ -708,6 +708,7 @@
 #define REL_DIAL		0x07
 #define REL_WHEEL		0x08
 #define REL_MISC		0x09
+#define REL_WHEEL_HI_RES	0x0a
 #define REL_MAX			0x0f
 #define REL_CNT			(REL_MAX+1)
 
-- 
2.18.0.1017.ga543ac7ca45-goog

[PATCH 2/3] Create a utility class for counting scroll events

From: Harry Cutts <hidden>
Date: 2018-08-23 18:31:46

To avoid code duplication, this class counts high-resolution scroll
movements and emits the legacy low-resolution events when appropriate.
Drivers should create one instance for each scroll wheel that they
need to handle.

Signed-off-by: Harry Cutts <redacted>
---

 drivers/hid/hid-input.c | 44 +++++++++++++++++++++++++++++++++++++++++
 include/linux/hid.h     | 28 ++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 4e94ea3e280a..4ee23b297472 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1826,3 +1826,47 @@ 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
+ * 256ths of a millimeter 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 often rest 7/8ths of a notch from the previous notch
+	 * after slow movement, so we want the threshold for low-res events in
+	 * between 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->mm256_per_hi_res_unit);
+
+	counter->remainder += hi_res_value;
+	if (abs(counter->remainder) >= threshold) {
+		/* Add (or subtract) 1 because we want to trigger when 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);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 834e6461a690..b7bc0b2faf4f 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1138,6 +1138,34 @@ 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.
+ * @mm256_per_hi_res_unit: the amount moved by the user's finger for each
+ *                         high-resolution unit reported by the mouse, in 256ths
+ *                         of a millimetre.
+ * @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 mm256_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);
-- 
2.18.0.1017.ga543ac7ca45-goog

[PATCH 3/3] Enable high-resolution scrolling on Logitech mice

From: Harry Cutts <hidden>
Date: 2018-08-23 18:31:55

There are three features used by various Logitech mice for
high-resolution scrolling: the fast scrolling bit in HID++ 1.0, and the
x2120 and x2121 features in HID++ 2.0 and above. This patch supports
all three, and uses the multiplier reported by the mouse for the HID++
2.0+ features.

The full list of product IDs of mice which support high-resolution
scrolling was provided by Logitech, but the patch was tested using the
following mice (over both Bluetooth and Unifying where applicable):

* HID++ 1.0: Anywhere MX, Performance MX
* x2120: M560
* x2121: MX Anywhere 2, MX Master 2S

Signed-off-by: Harry Cutts <redacted>
---

 drivers/hid/hid-ids.h            |  15 ++
 drivers/hid/hid-logitech-hidpp.c | 341 ++++++++++++++++++++++++++++---
 drivers/hid/hid-quirks.c         |  11 +
 3 files changed, 340 insertions(+), 27 deletions(-)
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 79bdf0c7e351..64fbe6174189 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -717,6 +717,21 @@
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C01A	0xc01a
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C05A	0xc05a
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C06A	0xc06a
+/*
+ * The following mice have different IDs over Bluetooth than Logitech Unifying
+ * protocol, hence the _BT suffix.
+ */
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1	0xb014
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2	0xb016
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT		0xb015
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1	0xb013
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2	0xb018
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3	0xb01f
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT	0xb01a
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1	0xb012
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2	0xb017
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3	0xb01e
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT	0xb019
 #define USB_DEVICE_ID_LOGITECH_RUMBLEPAD_CORD	0xc20a
 #define USB_DEVICE_ID_LOGITECH_RUMBLEPAD	0xc211
 #define USB_DEVICE_ID_LOGITECH_EXTREME_3D	0xc215
diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 19cc980eebce..17598b87f1b7 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/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 */
@@ -400,32 +409,53 @@ 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;
 	u8 params[3] = { 0 };
 
 	ret = hidpp_send_rap_command_sync(hidpp_dev,
-					REPORT_ID_HIDPP_SHORT,
-					HIDPP_GET_REGISTER,
-					HIDPP_REG_GENERAL,
-					NULL, 0, &response);
+					  REPORT_ID_HIDPP_SHORT,
+					  HIDPP_GET_REGISTER,
+					  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,
-					params, 3, &response);
+					   REPORT_ID_HIDPP_SHORT,
+					   HIDPP_SET_REGISTER,
+					   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 scrolling was called "fast scrolling". */
+static int hidpp10_enable_fast_scrolling(struct hidpp_device *hidpp_dev)
+{
+	return hidpp10_set_register_bit(hidpp_dev, HIDPP_REG_FEATURES, 0, 6);
 }
 
 #define HIDPP_REG_BATTERY_STATUS			0x07
@@ -1136,6 +1166,101 @@ 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:
+	*multiplier = 8;
+	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 +2524,8 @@ 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 +2653,71 @@ 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.
+ * @mm256_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 mm256_per_hi_res_unit;
+};
+
+static struct hi_res_scroll_info hi_res_scroll_devices[] = {
+	{ /* Anywhere MX */
+	  .product_id = 0x1017, .mm256_per_hi_res_unit = 114 },
+	{ /* Performance MX */
+	  .product_id = 0x101a, .mm256_per_hi_res_unit = 104 },
+	{ /* M560 */
+	  .product_id = 0x402d, .mm256_per_hi_res_unit = 111 },
+	{ /* MX Master 2S */
+	  .product_id = 0x4069, .mm256_per_hi_res_unit = 104 },
+	{ .product_id = USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT,
+	  .mm256_per_hi_res_unit = 104 },
+};
+
+static int hi_res_scroll_look_up_mm256(__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].mm256_per_hi_res_unit;
+	}
+	return 104;
+}
+
+static int hi_res_scroll_enable(struct hidpp_device *hidpp)
+{
+	int ret;
+	u8 multiplier;
+
+	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_fast_scrolling(hidpp);
+		multiplier = 8;
+	}
+	if (ret)
+		return ret;
+
+	hidpp->vertical_wheel_counter.resolution_multiplier = multiplier;
+	hidpp->vertical_wheel_counter.mm256_per_hi_res_unit =
+		hi_res_scroll_look_up_mm256(hidpp->hid_dev->product);
+	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 +2886,25 @@ 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)
+{
+	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 +3116,9 @@ 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 +3304,97 @@ 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 M336, M337, and M535 */
+	  HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2),
+	  .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 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT),
+	  .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 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Anywhere 2S */
+	  LDJ_DEVICE(0x406a), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT),
+	  .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 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3),
+	  .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ /* Mouse Logitech MX Master 2S */
+	  LDJ_DEVICE(0x4069), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+		USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT),
+	  .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 +3403,19 @@ 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,
diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
index 249d49b6b16c..7926c275f258 100644
--- a/drivers/hid/hid-quirks.c
+++ b/drivers/hid/hid-quirks.c
@@ -463,6 +463,17 @@ static const struct hid_device_id hid_have_special_driver[] = {
 #endif
 #if IS_ENABLED(CONFIG_HID_LOGITECH_HIDPP)
 	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_T651) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_G920_WHEEL) },
 #endif
 #if IS_ENABLED(CONFIG_HID_LOGITECH_DJ)
-- 
2.18.0.1017.ga543ac7ca45-goog

Re: [PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2018-08-23 18:42:26

On Thu, Aug 23, 2018 at 11:30:55AM -0700, Harry Cutts wrote:
This event code represents scroll reports from high-resolution wheels,
and will be used by future patches in this series. See the linux-input
"Reporting high-resolution scroll events" thread [0] for more details.

[0]: https://www.spinics.net/lists/linux-input/msg57380.html

Signed-off-by: Harry Cutts <redacted>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Jiri, Benjamin, feel free to merge through HID tree if the rest is
acceptable.

Thanks.

-- 
Dmitry

Re: [PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Matthew Wilcox <willy@infradead.org>
Date: 2018-08-23 18:57:25

On Thu, Aug 23, 2018 at 11:30:55AM -0700, Harry Cutts wrote:
+  - 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 256ths of a millimeter.
Is it too late to change this to an actual unit like micrometres?

Re: [PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2018-08-23 19:01:38

On Thu, Aug 23, 2018 at 11:57:22AM -0700, Matthew Wilcox wrote:
On Thu, Aug 23, 2018 at 11:30:55AM -0700, Harry Cutts wrote:
quoted
+  - 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 256ths of a millimeter.
Is it too late to change this to an actual unit like micrometres?
No love for imperial roots? Sure, micrometers would work too I think.

-- 
Dmitry

Re: [PATCH 3/3] Enable high-resolution scrolling on Logitech mice

From: Benjamin Tissoires <hidden>
Date: 2018-08-28 08:47:19

Hi Harry,

On Thu, Aug 23, 2018 at 8:31 PM Harry Cutts [off-list ref] wrote:
There are three features used by various Logitech mice for
high-resolution scrolling: the fast scrolling bit in HID++ 1.0, and the
x2120 and x2121 features in HID++ 2.0 and above. This patch supports
all three, and uses the multiplier reported by the mouse for the HID++
2.0+ features.

The full list of product IDs of mice which support high-resolution
scrolling was provided by Logitech, but the patch was tested using the
following mice (over both Bluetooth and Unifying where applicable):

* HID++ 1.0: Anywhere MX, Performance MX
* x2120: M560
* x2121: MX Anywhere 2, MX Master 2S

Signed-off-by: Harry Cutts <redacted>
Patches 1 and 2 look fine (I'd rather have the micrometers too).
I have more concerns about this one.
My main issue is that this patch both reshuffle existing parts and add
new features, which makes it hard to review.
quoted hunk
---

 drivers/hid/hid-ids.h            |  15 ++
 drivers/hid/hid-logitech-hidpp.c | 341 ++++++++++++++++++++++++++++---
 drivers/hid/hid-quirks.c         |  11 +
 3 files changed, 340 insertions(+), 27 deletions(-)
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 79bdf0c7e351..64fbe6174189 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -717,6 +717,21 @@
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C01A      0xc01a
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C05A      0xc05a
 #define USB_DEVICE_ID_LOGITECH_MOUSE_C06A      0xc06a
+/*
+ * The following mice have different IDs over Bluetooth than Logitech Unifying
+ * protocol, hence the _BT suffix.
+ */
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1  0xb014
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2  0xb016
+#define USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT           0xb015
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1 0xb013
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2 0xb018
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3 0xb01f
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT 0xb01a
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1     0xb012
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2     0xb017
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3     0xb01e
+#define USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT   0xb019
 #define USB_DEVICE_ID_LOGITECH_RUMBLEPAD_CORD  0xc20a
 #define USB_DEVICE_ID_LOGITECH_RUMBLEPAD       0xc211
 #define USB_DEVICE_ID_LOGITECH_EXTREME_3D      0xc215
diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 19cc980eebce..17598b87f1b7 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/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 */
@@ -400,32 +409,53 @@ 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;
        u8 params[3] = { 0 };

        ret = hidpp_send_rap_command_sync(hidpp_dev,
-                                       REPORT_ID_HIDPP_SHORT,
-                                       HIDPP_GET_REGISTER,
-                                       HIDPP_REG_GENERAL,
-                                       NULL, 0, &response);
+                                         REPORT_ID_HIDPP_SHORT,
+                                         HIDPP_GET_REGISTER,
+                                         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,
-                                       params, 3, &response);
+                                          REPORT_ID_HIDPP_SHORT,
+                                          HIDPP_SET_REGISTER,
+                                          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);
+}
This hunk should be dealt in a separate patch (including the one function below)
quoted hunk
+
+#define HIDPP_REG_FEATURES                             0x01
+
+/* On HID++ 1.0 devices, high-res scrolling was called "fast scrolling". */
+static int hidpp10_enable_fast_scrolling(struct hidpp_device *hidpp_dev)
+{
+       return hidpp10_set_register_bit(hidpp_dev, HIDPP_REG_FEATURES, 0, 6);
 }

 #define HIDPP_REG_BATTERY_STATUS                       0x07
@@ -1136,6 +1166,101 @@ 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:
+       *multiplier = 8;
+       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 +2524,8 @@ 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);
The conversion input_report_rel(... REL_WHEEL,...) to
hid_scroll_counter_handle_scroll() should be dealt in a separate
patch.
quoted hunk
                input_sync(mydata->input);
        }
@@ -2527,6 +2653,71 @@ 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.
+ * @mm256_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 mm256_per_hi_res_unit;
+};
+
+static struct hi_res_scroll_info hi_res_scroll_devices[] = {
+       { /* Anywhere MX */
+         .product_id = 0x1017, .mm256_per_hi_res_unit = 114 },
+       { /* Performance MX */
+         .product_id = 0x101a, .mm256_per_hi_res_unit = 104 },
+       { /* M560 */
+         .product_id = 0x402d, .mm256_per_hi_res_unit = 111 },
+       { /* MX Master 2S */
+         .product_id = 0x4069, .mm256_per_hi_res_unit = 104 },
+       { .product_id = USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT,
+         .mm256_per_hi_res_unit = 104 },
+};
+
+static int hi_res_scroll_look_up_mm256(__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].mm256_per_hi_res_unit;
+       }
+       return 104;
104?
quoted hunk
+}
+
+static int hi_res_scroll_enable(struct hidpp_device *hidpp)
+{
+       int ret;
+       u8 multiplier;
+
+       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_fast_scrolling(hidpp);
+               multiplier = 8;
+       }
+       if (ret)
+               return ret;
+
+       hidpp->vertical_wheel_counter.resolution_multiplier = multiplier;
+       hidpp->vertical_wheel_counter.mm256_per_hi_res_unit =
+               hi_res_scroll_look_up_mm256(hidpp->hid_dev->product);
+       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 +2886,25 @@ 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)
+{
+       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;
You are using usage_table to force the .event function to be called
only on the WHEEL events. This is correct, but I have a feeling this
will be harder to understand when we are going to extend the .event()
function for other events.
If you rather keep the cde that way, please add a comment at the
beginning of the function stating that we are only called against
WHEEL events because of usage_table.
quoted hunk
+
+       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 +3116,9 @@ 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 +3304,97 @@ 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),
The rewrite of the existing supported devices should be in a separate patch too.
quoted hunk
          .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 M336, M337, and M535 */
+         HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2),
+         .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 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT),
+         .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 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { /* Mouse Logitech MX Anywhere 2S */
+         LDJ_DEVICE(0x406a), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT),
+         .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 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3),
+         .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { /* Mouse Logitech MX Master 2S */
+         LDJ_DEVICE(0x4069), .driver_data = HIDPP_QUIRK_HI_RES_SCROLL_X2121 },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
+               USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT),
+         .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 +3403,19 @@ 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,
diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
index 249d49b6b16c..7926c275f258 100644
--- a/drivers/hid/hid-quirks.c
+++ b/drivers/hid/hid-quirks.c
@@ -463,6 +463,17 @@ static const struct hid_device_id hid_have_special_driver[] = {
 #endif
 #if IS_ENABLED(CONFIG_HID_LOGITECH_HIDPP)
        { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_T651) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT1) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M336_337_535_BT2) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_M720_BT) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT1) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT2) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2_BT3) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_ANYWHERE_2S_BT) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT1) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT2) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_BT3) },
+       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MOUSE_MX_MASTER_2S_BT) },
Since v4.16, this should not be required anymore. Please drop the hunk
if I am correct.

Cheers,
Benjamin
        { HID_USB_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_G920_WHEEL) },
 #endif
 #if IS_ENABLED(CONFIG_HID_LOGITECH_DJ)
--
2.18.0.1017.ga543ac7ca45-goog

Re: [PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Jiri Kosina <jikos@kernel.org>
Date: 2018-08-28 09:02:25

On Thu, 23 Aug 2018, Dmitry Torokhov wrote:
quoted
quoted
+  - 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 256ths of a millimeter.
Is it too late to change this to an actual unit like micrometres?
No love for imperial roots? Sure, micrometers would work too I think.
I don't really care strongly :) Is either of you going to update the 
patch? Otherwise I'll just apply as-is.

Thanks,

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH 1/3] Add the `REL_WHEEL_HI_RES` event code

From: Harry Cutts <hidden>
Date: 2018-08-28 17:49:49

Benjamin says he prefers micrometres, and I think I do to now that I
think about it (sticking with SI seems like a good idea), so I'll
update it in a V2.

Harry Cutts
Chrome OS Touch/Input team
Harry Cutts
Chrome OS Touch/Input team


On Tue, 28 Aug 2018 at 02:02, Jiri Kosina [off-list ref] wrote:
On Thu, 23 Aug 2018, Dmitry Torokhov wrote:
quoted
quoted
quoted
+  - 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 256ths of a millimeter.
Is it too late to change this to an actual unit like micrometres?
No love for imperial roots? Sure, micrometers would work too I think.
I don't really care strongly :) Is either of you going to update the
patch? Otherwise I'll just apply as-is.

Thanks,

--
Jiri Kosina
SUSE Labs
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