From ddec4ff683bbbb1e92e4fa30adcefe93b38c2cb0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ciar=C3=A1n=20Coffey?= Date: Fri, 10 Oct 2025 19:04:03 +0100 Subject: [PATCH] HID: Add hid-surface driver to filter BTN_0 (FN key) The Surface Aggregator Module firmware incorrectly reports the FN key as BTN_0 (button 256) through runtime HID events. This button can get stuck in pressed state, flooding the input system and breaking focus tracking in KWin Wayland compositor. Add a new hid-surface driver that filters BTN_0 events using the event callback. The FN key should be handled as a hardware modifier and not reported to the OS. Tested on Surface Laptop 4 AMD with KDE Plasma Wayland. After the fix: - FN key combinations work correctly (volume, brightness) - Focus tracking no longer breaks - Mouse clicks work on all windows Fixes: https://github.com/linux-surface/linux-surface/issues/1851 Patchset: hid-surface --- drivers/hid/Kconfig | 8 ++++ drivers/hid/Makefile | 1 + drivers/hid/hid-surface.c | 90 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 99 insertions(+) create mode 100644 drivers/hid/hid-surface.c diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig index 184a2b2f9..d2e308b25 100644 --- a/drivers/hid/Kconfig +++ b/drivers/hid/Kconfig @@ -1141,6 +1141,14 @@ config HID_SUNPLUS help Support for Sunplus wireless desktop. +config HID_SURFACE + tristate "Microsoft Surface" + depends on SURFACE_AGGREGATOR + help + Say Y here to enable HID driver for Microsoft Surface integrated + keyboard and touchpad. This driver filters out erroneous BTN_0 + (FN key) events that can cause input focus issues. + config HID_RMI tristate "Synaptics RMI4 device support" select RMI4_CORE diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile index 3190ece25..4d2891879 100644 --- a/drivers/hid/Makefile +++ b/drivers/hid/Makefile @@ -174,6 +174,7 @@ obj-$(CONFIG_INTEL_ISH_HID) += intel-ish-hid/ obj-$(CONFIG_AMD_SFH_HID) += amd-sfh-hid/ obj-$(CONFIG_SURFACE_HID_CORE) += surface-hid/ +obj-$(CONFIG_HID_SURFACE) += hid-surface.o obj-$(CONFIG_INTEL_THC_HID) += intel-thc-hid/ diff --git a/drivers/hid/hid-surface.c b/drivers/hid/hid-surface.c new file mode 100644 index 000000000..a171ea656 --- /dev/null +++ b/drivers/hid/hid-surface.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * HID driver for Microsoft Surface devices + * + * Copyright (c) 2025 Linux Surface Project + */ + +#include +#include +#include +#include + +#include "hid-ids.h" + +/* + * The Surface Aggregator Module firmware incorrectly reports the FN key + * as BTN_0 (button 256). This button can get stuck in pressed state, + * flooding the input system and breaking focus tracking in some + * compositors. Filter out BTN_0 as FN should be handled as a hardware + * modifier, not reported to the OS. + */ +static int surface_input_mapping(struct hid_device *hdev, struct hid_input *hi, + struct hid_field *field, struct hid_usage *usage, + unsigned long **bit, int *max) +{ + /* + * Filter BTN_0 during input mapping in case it appears in the + * HID descriptor (defense in depth). + */ + if (usage->type == EV_KEY && usage->code == BTN_0) + return -1; /* Don't map this usage */ + + return 0; /* Use default mapping */ +} + +static int surface_event(struct hid_device *hdev, struct hid_field *field, + struct hid_usage *usage, __s32 value) +{ + /* + * The Surface Aggregator Module firmware reports the FN key as BTN_0 + * at runtime. This button can get stuck in pressed state, flooding + * the input system and breaking focus tracking. Filter out these + * events as FN should be a hardware modifier, not reported to the OS. + */ + if (usage->type == EV_KEY && usage->code == BTN_0) + return 1; /* Event handled, don't process further */ + + return 0; /* Process event normally */ +} + +static int surface_probe(struct hid_device *hdev, const struct hid_device_id *id) +{ + int ret; + + ret = hid_parse(hdev); + if (ret) { + hid_err(hdev, "parse failed\n"); + return ret; + } + + ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT); + if (ret) { + hid_err(hdev, "hw start failed\n"); + return ret; + } + + return 0; +} + +static const struct hid_device_id surface_devices[] = { + { HID_DEVICE(BUS_HOST, HID_GROUP_GENERIC, + USB_VENDOR_ID_MICROSOFT, 0x09AE) }, /* Surface Keyboard */ + { HID_DEVICE(BUS_HOST, HID_GROUP_GENERIC, + USB_VENDOR_ID_MICROSOFT, 0x09AF) }, /* Surface Mouse/Touchpad */ + { } +}; +MODULE_DEVICE_TABLE(hid, surface_devices); + +static struct hid_driver surface_driver = { + .name = "surface", + .id_table = surface_devices, + .probe = surface_probe, + .input_mapping = surface_input_mapping, + .event = surface_event, +}; +module_hid_driver(surface_driver); + +MODULE_AUTHOR("Linux Surface Project"); +MODULE_DESCRIPTION("Microsoft Surface HID driver"); +MODULE_LICENSE("GPL"); -- 2.52.0 From 16174508fdd5cdfaebb39bc5c1747c09679b7a70 Mon Sep 17 00:00:00 2001 From: LegendaryFire Date: Wed, 24 Dec 2025 00:54:44 -0800 Subject: [PATCH] hid/multitouch: Prevent mode set on Surface Laptop Studio 2 touch pad Patchset: hid-surface --- drivers/hid/hid-multitouch.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c index 0eb4f7d12..8f2ed29b4 100644 --- a/drivers/hid/hid-multitouch.c +++ b/drivers/hid/hid-multitouch.c @@ -82,6 +82,7 @@ MODULE_LICENSE("GPL"); #define MT_QUIRK_APPLE_TOUCHBAR BIT(23) #define MT_QUIRK_HAS_TYPE_COVER_BACKLIGHT BIT(24) #define MT_QUIRK_HAS_TYPE_COVER_TABLET_MODE_SWITCH BIT(25) +#define MT_QUIRK_SKIP_MODESET_ON_HW_OPEN_CLOSE BIT(26) #define MT_INPUTMODE_TOUCHSCREEN 0x02 #define MT_INPUTMODE_TOUCHPAD 0x03 @@ -242,6 +243,7 @@ static void mt_post_parse(struct mt_device *td, struct mt_application *app); #define MT_CLS_SMART_TECH 0x0113 #define MT_CLS_APPLE_TOUCHBAR 0x0114 #define MT_CLS_WIN_8_MS_SURFACE_TYPE_COVER 0x0115 +#define MT_CLS_SURFACE_TOUCHPAD 0x0116 #define MT_CLS_SIS 0x0457 #define MT_DEFAULT_MAXCONTACT 10 @@ -449,6 +451,10 @@ static const struct mt_class mt_classes[] = { MT_QUIRK_WIN8_PTP_BUTTONS, .export_all_inputs = true }, + { .name = MT_CLS_SURFACE_TOUCHPAD, + .quirks = MT_QUIRK_ALWAYS_VALID | + MT_QUIRK_SKIP_MODESET_ON_HW_OPEN_CLOSE + }, { } }; @@ -2180,11 +2186,30 @@ static void mt_remove(struct hid_device *hdev) static void mt_on_hid_hw_open(struct hid_device *hdev) { + /* + * Some devices (e.g. Surface Laptop Studio 2 touchpad) can get stuck + * non-functional if we change touchpad reporting modes from the HID + * open/close hooks. Avoid mode switching on hw_open/hw_close for + * those devices. + */ + struct mt_device *td = hid_get_drvdata(hdev); + if (td && td->mtclass.quirks & MT_QUIRK_SKIP_MODESET_ON_HW_OPEN_CLOSE) + return; mt_set_modes(hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_ALL); } static void mt_on_hid_hw_close(struct hid_device *hdev) { + /* + * Some devices (e.g. Surface Laptop Studio 2 touchpad) can get stuck + * non-functional if we change touchpad reporting modes from the HID + * open/close hooks. Avoid mode switching on hw_open/hw_close for + * those devices. + */ + struct mt_device *td = hid_get_drvdata(hdev); + if (td && td->mtclass.quirks & MT_QUIRK_SKIP_MODESET_ON_HW_OPEN_CLOSE) + return; + mt_set_modes(hdev, HID_LATENCY_HIGH, TOUCHPAD_REPORT_NONE); } @@ -2621,6 +2646,11 @@ static const struct hid_device_id mt_devices[] = { HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, USB_VENDOR_ID_MICROSOFT, 0x09c0) }, + /* Microsoft Surface touch pad */ + { .driver_data = MT_CLS_SURFACE_TOUCHPAD, + HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, + USB_VENDOR_ID_MICROSOFT, 0x0C46) }, + /* Google MT devices */ { .driver_data = MT_CLS_GOOGLE, HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, USB_VENDOR_ID_GOOGLE, -- 2.52.0