From: Lauri Saurus <saurla@saurla.com>
Date: Mon, 18 May 2026 19:28:50 +0000 (+0000)
Subject: HID: logitech-hidpp: sync wheel multiplier on wheel mode changes
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f0866517be9345d8245d32b722574b8aecccb348;p=thirdparty%2Fkernel%2Flinux.git

HID: logitech-hidpp: sync wheel multiplier on wheel mode changes

The hid-logitech-hidpp driver enables high resolution scrolling on
device connect for capable HID++ 2.0 devices. Driver also reads the
wheel capability and caches the returned high resolution wheel scroll
multiplier, that is used for scroll scaling when handling wheel scroll
events.

Wheel mode can also be set externally through HID++ requests, which
can leave the cached multiplier stale and cause incorrect scroll
scaling. If external SetWheelMode HID++ request sets the mode to
low resolution, the cached multiplier is not updated accordingly. This
causes extremely slow scrolling since driver expects multiple wheel
scroll events per detent but is only getting one.

The fix listens for HID++ SetWheelMode request responses and updates
the wheel scroll multiplier based on the set high resolution scroll
mode. The fix has been tested with Logitech G502X lightspeed mouse.

Signed-off-by: Lauri Saurus <saurla@saurla.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
---

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 1990ba5b26ea6..70ba1a5e40d8e 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -206,6 +206,9 @@ struct hidpp_device {
 
 	u8 wireless_feature_index;
 
+	int hires_wheel_multiplier;
+	u8 hires_wheel_feature_index;
+
 	bool connected_once;
 };
 
@@ -3709,6 +3712,7 @@ static int hi_res_scroll_enable(struct hidpp_device *hidpp)
 		multiplier = 1;
 	}
 
+	hidpp->hires_wheel_multiplier = multiplier;
 	hidpp->vertical_wheel_counter.wheel_multiplier = multiplier;
 	hid_dbg(hidpp->hid_dev, "wheel multiplier = %d\n", multiplier);
 	return 0;
@@ -3719,6 +3723,7 @@ static int hidpp_initialize_hires_scroll(struct hidpp_device *hidpp)
 	int ret;
 	unsigned long capabilities;
 
+	hidpp->hires_wheel_feature_index = 0xff;
 	capabilities = hidpp->capabilities;
 
 	if (hidpp->protocol_major >= 2) {
@@ -3728,6 +3733,7 @@ static int hidpp_initialize_hires_scroll(struct hidpp_device *hidpp)
 					     &feature_index);
 		if (!ret) {
 			hidpp->capabilities |= HIDPP_CAPABILITY_HIDPP20_HI_RES_WHEEL;
+			hidpp->hires_wheel_feature_index = feature_index;
 			hid_dbg(hidpp->hid_dev, "Detected HID++ 2.0 hi-res scroll wheel\n");
 			return 0;
 		}
@@ -3750,6 +3756,31 @@ static int hidpp_initialize_hires_scroll(struct hidpp_device *hidpp)
 	return 0;
 }
 
+static int hidpp20_hires_wheel_raw_event(struct hidpp_device *hidpp,
+						u8 *data, int size)
+{
+	if (hidpp->hires_wheel_feature_index == 0xff)
+		return 0;
+
+	if (size < 5)
+		return 0;
+
+	if (data[0] != REPORT_ID_HIDPP_LONG ||
+	    data[2] != hidpp->hires_wheel_feature_index)
+		return 0;
+
+	if ((data[3] & 0xf0) == CMD_HIRES_WHEEL_SET_WHEEL_MODE) {
+		u8 mode = data[4];
+		bool hires = (mode & 0x02) != 0;
+		int new_multiplier = (hires && hidpp->hires_wheel_multiplier > 0)
+			? hidpp->hires_wheel_multiplier : 1;
+		hidpp->vertical_wheel_counter.wheel_multiplier = new_multiplier;
+		return 1;
+	}
+
+	return 0;
+}
+
 /* -------------------------------------------------------------------------- */
 /* Generic HID++ devices                                                      */
 /* -------------------------------------------------------------------------- */
@@ -3946,6 +3977,12 @@ static int hidpp_raw_hidpp_event(struct hidpp_device *hidpp, u8 *data,
 			return ret;
 	}
 
+	if (hidpp->capabilities & HIDPP_CAPABILITY_HIDPP20_HI_RES_WHEEL) {
+		ret = hidpp20_hires_wheel_raw_event(hidpp, data, size);
+		if (ret != 0)
+			return ret;
+	}
+
 	return 0;
 }