On Mon, 8 Jun 2026, Dave Carey wrote: > The Lenovo Yoga Book 9 14IAH10 ships with a detachable Bluetooth keyboard > that magnetically attaches to the bottom (secondary) screen in one of two > positions. The Embedded Controller tracks the attachment state in a 2-bit > field called BKBD Please add a define for the field then with GENMASK() and extract it with FIELD_GET(). Don't forget to add headers. > and signals changes via WMI event GUID > 806BD2A2-177B-481D-BFB5-3BA0BB4A2285 (notify ID 0xEB on the WM10 ACPI > device, _UID "GMZN"). > > The device contains embedded BMOF data (WQDD, 20705 bytes) documenting > both WMI interfaces used by this driver: > > LENOVO_BTKBD_EVENT (event GUID): WmiDataId(1) uint32 Status. > The ACPI _WED(0xEB) method returns EC.BKBD directly as an integer, > so the notify callback receives BKBD without a separate query. > > LENOVO_FEATURE_STATUS_DATA (block GUID, WQAF method): returns an > 8-byte buffer {uint32 IDs=0x00060000, uint32 Status=BKBD}. > Used for the initial state read on probe and after resume. > > BKBD encoding: > 0 = keyboard detached > 1 = keyboard docked on top half of bottom screen > 2 = keyboard docked on bottom half of bottom screen > 3 = reserved (not observed in practice) > > This driver: > - Registers two WMI drivers: one on the event GUID (LENOVO_BTKBD_EVENT) > and one on the block GUID (LENOVO_FEATURE_STATUS_DATA). > - On probe, reads initial BKBD state via wmidev_block_query() on the > block device; whichever driver probes last triggers the initial read. > - On WMI notification, reads BKBD directly from the event data integer > (ACPI _WED(0xEB) returns EC.BKBD) without a redundant WQAF call. > - Reports SW_TABLET_MODE=1 when detached, SW_TABLET_MODE=0 when docked > in either position (a physical keyboard is present in both cases). > - Exposes the raw BKBD value via read-only sysfs attribute > "keyboard_position". > - Re-reads BKBD state on resume from suspend or hibernation. > > Tested on: Lenovo Yoga Book 9 14IAH10 (model 83KJ), kernel 7.0. > > Signed-off-by: Dave Carey > --- > v6: > - Submitted as 2/2; patch 1/2 adds a DMI early-exit to lenovo-ymc to > prevent duplicate SW_TABLET_MODE input nodes on the YB9. > > v5: > - Rewrote as two WMI drivers (event + block) to avoid the deprecated > wmi_query_block() API: event driver owns the GUID that delivers > notifications, block driver owns the GUID used for querying state. > Either can probe first; both probe callbacks check whether the other > has already probed and fire the initial read when both are ready. > - Use wmidev_block_query() on the block wmi_device directly (replaces > the deprecated wmi_query_block()). > - In the notify callback, read BKBD directly from the event data integer > passed by the WMI core (_WED(0xEB) returns EC.BKBD; confirmed by > decoding the embedded BMOF from WQDD). Eliminates the redundant WQAF > call that v4 made on every notification. > - Documented the two BMOF classes (LENOVO_BTKBD_EVENT and > LENOVO_FEATURE_STATUS_DATA) with field layouts in the commit message > and file header. > - sysfs keyboard_position: output bare integer, drop the parenthetical > position-name suffix that a couple of reviewers found non-standard. > - Set .no_singleton = true on both WMI drivers (was missing from block > driver in v4). > - Add PM resume callback (yb9_kbdock_resume) to re-read BKBD state > after suspend/hibernation. > > v4: > - Dropped module_wmi_driver(); registered two WMI drivers manually to > allow sharing state. module_init/exit pair registers/unregisters > both. > - Added ATTRIBUTE_GROUPS() and .dev_groups for the sysfs attribute. > - sysfs show: performed a live query instead of returning a cached value. > > v3: > - Switched to devm_input_allocate_device(). > - Added DMI guard (dmi_check_system) to reject non-YB9 machines. > - Removed redundant MODULE_DEVICE_TABLE on block driver. > > v2: > - Added .no_singleton = true on the event WMI driver. > - Added PM suspend/resume skeleton. > - Fixed MODULE_LICENSE to "GPL" (was "GPL v2"). > > .../testing/sysfs-driver-lenovo-yb9-kbdock | 19 + > MAINTAINERS | 7 + > drivers/platform/x86/lenovo/Kconfig | 14 + > drivers/platform/x86/lenovo/Makefile | 1 + > drivers/platform/x86/lenovo/yb9-kbdock.c | 324 ++++++++++++++++++ > 5 files changed, 365 insertions(+) > create mode 100644 Documentation/ABI/testing/sysfs-driver-lenovo-yb9-kbdock > create mode 100644 drivers/platform/x86/lenovo/yb9-kbdock.c > > diff --git a/Documentation/ABI/testing/sysfs-driver-lenovo-yb9-kbdock b/Documentation/ABI/testing/sysfs-driver-lenovo-yb9-kbdock > new file mode 100644 > index 0000000..04e5293 > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-driver-lenovo-yb9-kbdock > @@ -0,0 +1,19 @@ > +What: /sys/bus/wmi/drivers/lenovo-yb9-kbdock//keyboard_position > +Date: April 2026 > +KernelVersion: 6.10 > +Contact: Dave Carey > +Description: > + Read-only attribute reporting the current keyboard dock position > + as reported by the Embedded Controller on the Lenovo Yoga Book 9 > + 14IAH10. > + > + Possible values: > + > + == ============================================================= > + 0 keyboard is not docked to any screen (detached) > + 1 keyboard docked on the top half of the bottom screen > + 2 keyboard docked on the bottom half of the bottom screen > + == ============================================================= > + > + SW_TABLET_MODE input events are also emitted: 0 when the keyboard > + is docked (either position), 1 when detached. > diff --git a/MAINTAINERS b/MAINTAINERS > index d1cc0e1..00e8275 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -14479,6 +14479,13 @@ L: platform-driver-x86@vger.kernel.org > S: Maintained > F: drivers/platform/x86/lenovo/wmi-hotkey-utilities.c > > +LENOVO YOGA BOOK 9 KEYBOARD DOCK DRIVER > +M: Dave Carey > +L: platform-driver-x86@vger.kernel.org > +S: Maintained > +F: Documentation/ABI/testing/sysfs-driver-lenovo-yb9-kbdock > +F: drivers/platform/x86/lenovo/yb9-kbdock.c > + > LETSKETCH HID TABLET DRIVER > M: Hans de Goede > L: linux-input@vger.kernel.org > diff --git a/drivers/platform/x86/lenovo/Kconfig b/drivers/platform/x86/lenovo/Kconfig > index 9c48487..938b361 100644 > --- a/drivers/platform/x86/lenovo/Kconfig > +++ b/drivers/platform/x86/lenovo/Kconfig > @@ -43,6 +43,20 @@ config LENOVO_WMI_CAMERA > To compile this driver as a module, choose M here: the module > will be called lenovo-wmi-camera. > > +config LENOVO_YB9_KBDOCK > + tristate "Lenovo Yoga Book 9 keyboard dock detection" > + depends on ACPI_WMI > + depends on DMI > + depends on INPUT > + help > + Say Y here to enable keyboard dock detection on the Lenovo Yoga Book 9 > + 14IAH10. The detachable Bluetooth keyboard magnetically attaches to > + either screen; this driver reports SW_TABLET_MODE input events based > + on the attachment state and exposes the raw position in sysfs. > + > + To compile this driver as a module, choose M here: the module will be > + called lenovo-yb9-kbdock. > + > config LENOVO_YMC > tristate "Lenovo Yoga Tablet Mode Control" > depends on ACPI_WMI > diff --git a/drivers/platform/x86/lenovo/Makefile b/drivers/platform/x86/lenovo/Makefile > index 7b2128e..2842d7d 100644 > --- a/drivers/platform/x86/lenovo/Makefile > +++ b/drivers/platform/x86/lenovo/Makefile > @@ -8,6 +8,7 @@ obj-$(CONFIG_THINKPAD_LMI) += think-lmi.o > obj-$(CONFIG_THINKPAD_ACPI) += thinkpad_acpi.o > > lenovo-target-$(CONFIG_LENOVO_WMI_HOTKEY_UTILITIES) += wmi-hotkey-utilities.o > +lenovo-target-$(CONFIG_LENOVO_YB9_KBDOCK) += yb9-kbdock.o > lenovo-target-$(CONFIG_LENOVO_YMC) += ymc.o > lenovo-target-$(CONFIG_YOGABOOK) += yogabook.o > lenovo-target-$(CONFIG_YT2_1380) += yoga-tab2-pro-1380-fastcharger.o > diff --git a/drivers/platform/x86/lenovo/yb9-kbdock.c b/drivers/platform/x86/lenovo/yb9-kbdock.c > new file mode 100644 > index 0000000..28a3ec7 > --- /dev/null > +++ b/drivers/platform/x86/lenovo/yb9-kbdock.c > @@ -0,0 +1,324 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Lenovo Yoga Book 9 keyboard-dock detection > + * > + * The Yoga Book 9 ships with a detachable Bluetooth keyboard that magnetically > + * attaches to the bottom screen in one of two positions. The EC tracks > + * attachment state in a 2-bit field called BKBD and signals changes via WMI > + * event 0xEB on the WM10 ACPI device (_UID "GMZN"). > + * > + * BKBD values: > + * 0 = keyboard detached > + * 1 = keyboard docked on the top half of the bottom screen > + * 2 = keyboard docked on the bottom half of the bottom screen > + * 3 = reserved / not observed > + * > + * Two WMI interfaces are used (documented in embedded BMOF, WQDD, 20705 bytes): > + * > + * LENOVO_BTKBD_EVENT (event GUID, 806BD2A2-...) > + * WmiDataId(1) uint32 Status — _WED(0xEB) returns EC.BKBD directly. > + * The notify callback receives BKBD as an integer; no separate query needed. > + * > + * LENOVO_FEATURE_STATUS_DATA (block GUID, E7F300FA-...) > + * WmiDataId(1) uint32 IDs = 0x00060000 (feature selector) > + * WmiDataId(2) uint32 Status = BKBD value > + * Used on probe and resume to read initial state. > + * > + * SW_TABLET_MODE=1 is reported when the keyboard is detached; > + * SW_TABLET_MODE=0 when docked in either position (keyboard present). > + * The raw BKBD value is exposed via the sysfs attribute "keyboard_position". > + * > + * Copyright (C) 2026 Dave Carey > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define YB9_KBDOCK_EVENT_GUID "806BD2A2-177B-481D-BFB5-3BA0BB4A2285" > +#define YB9_KBDOCK_QUERY_GUID "E7F300FA-21CD-4003-ADAC-2696135982E6" > + > +/* BKBD encoding */ > +#define BKBD_DETACHED 0 > +#define BKBD_TOP_HALF 1 > +#define BKBD_BOTTOM_HALF 2 > + > +static const struct dmi_system_id yb9_kbdock_dmi_table[] = { > + { > + /* Lenovo Yoga Book 9 14IAH10 */ > + .matches = { > + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), > + DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"), > + }, > + }, > + { } > +}; > + > +/* > + * Shared state between the event and block WMI drivers. Protected by lock. > + * The lock may be held across wmidev_query_block() calls (which can sleep); > + * block_remove() acquires the lock before clearing block_wdev, ensuring > + * block_wdev remains valid for the duration of any in-progress query. > + */ > +static struct { > + struct mutex lock; Please add a short comment here on the same line too about what it protects. > + struct input_dev *input_dev; /* set by event probe */ > + struct wmi_device *block_wdev; /* set by block probe */ > +} yb9; > + > +/* > + * Read BKBD from the block device via wmidev_block_query(). > + * Returns 0-3 on success, -errno on failure. Caller must hold yb9.lock. To match kerneldoc formatting guidelines, use: Context: Caller must hold yb9.lock. Returns: > + */ > +static int yb9_kbdock_query_locked(struct device *log_dev) > +{ > + union acpi_object *obj; > + u32 bkbd; > + > + if (!yb9.block_wdev) > + return -ENODEV; > + > + obj = wmidev_block_query(yb9.block_wdev, 0); This is interface is deprecated: * wmidev_block_query - Return contents of a WMI block (deprectated) > + if (!obj) { > + dev_warn(log_dev, "WQAF returned NULL\n"); Please add include. > + return -EIO; > + } > + > + /* > + * LENOVO_FEATURE_STATUS_DATA: 8-byte buffer {IDs=0x00060000, Status=BKBD}. > + */ > + if (obj->type == ACPI_TYPE_BUFFER && obj->buffer.length >= 8) { > + memcpy(&bkbd, obj->buffer.pointer + 4, sizeof(bkbd)); > + bkbd &= 0x3; > + } else if (obj->type == ACPI_TYPE_INTEGER) { > + bkbd = obj->integer.value & 0x3; > + } else { > + dev_warn(log_dev, "WQAF: unexpected type %d len %u\n", > + obj->type, > + obj->type == ACPI_TYPE_BUFFER ? obj->buffer.length : 0); > + kfree(obj); > + return -EIO; > + } > + > + kfree(obj); Please add include for kfree(). With the new WMI API, please use __free() to avoid dupli > + return (int)bkbd; > +} > + > +/* Report SW_TABLET_MODE from BKBD. Caller must hold yb9.lock. */ > +static void yb9_kbdock_report_locked(int bkbd, struct device *log_dev) > +{ > + int tablet = (bkbd == BKBD_DETACHED) ? 1 : 0; > + > + input_report_switch(yb9.input_dev, SW_TABLET_MODE, tablet); > + input_sync(yb9.input_dev); > + dev_dbg(log_dev, "BKBD=%d SW_TABLET_MODE=%d\n", bkbd, tablet); > +} > + > +/* ------------------------------------------------------------------ > + * sysfs > + * ------------------------------------------------------------------ */ > + > +static ssize_t keyboard_position_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + int bkbd; > + > + mutex_lock(&yb9.lock); > + bkbd = yb9_kbdock_query_locked(dev); > + mutex_unlock(&yb9.lock); > + > + if (bkbd < 0) > + return bkbd; > + return sysfs_emit(buf, "%u\n", (unsigned int)bkbd); > +} > +static DEVICE_ATTR_RO(keyboard_position); > + > +static struct attribute *yb9_kbdock_attrs[] = { > + &dev_attr_keyboard_position.attr, > + NULL, > +}; > +ATTRIBUTE_GROUPS(yb9_kbdock); > + > +/* ------------------------------------------------------------------ > + * Event WMI driver — LENOVO_BTKBD_EVENT > + * ------------------------------------------------------------------ */ > + > +static void yb9_kbdock_notify(struct wmi_device *wdev, union acpi_object *data) > +{ > + u32 bkbd; > + > + /* > + * _WED(0xEB) returns EC.BKBD directly as an integer > + * (LENOVO_BTKBD_EVENT WmiDataId(1) uint32 Status). > + */ > + if (!data || data->type != ACPI_TYPE_INTEGER) { > + dev_warn(&wdev->dev, "unexpected event data type %d\n", > + data ? data->type : -1); > + return; > + } > + bkbd = data->integer.value & 0x3; > + > + mutex_lock(&yb9.lock); guard() > + if (yb9.input_dev) > + yb9_kbdock_report_locked(bkbd, &wdev->dev); > + mutex_unlock(&yb9.lock); > +} > + > +static int yb9_kbdock_event_probe(struct wmi_device *wdev, const void *ctx) > +{ > + struct input_dev *input_dev; > + int bkbd, err; > + > + if (!dmi_check_system(yb9_kbdock_dmi_table)) > + return -ENODEV; > + > + input_dev = devm_input_allocate_device(&wdev->dev); > + if (!input_dev) > + return -ENOMEM; > + > + input_dev->name = "Lenovo Yoga Book 9 keyboard dock switch"; > + input_dev->phys = YB9_KBDOCK_EVENT_GUID "/input0"; > + input_dev->id.bustype = BUS_HOST; > + input_set_capability(input_dev, EV_SW, SW_TABLET_MODE); > + > + err = input_register_device(input_dev); > + if (err) > + return err; > + > + mutex_lock(&yb9.lock); guard() > + yb9.input_dev = input_dev; > + /* Read initial state if the block device has already probed. */ > + if (yb9.block_wdev) { > + bkbd = yb9_kbdock_query_locked(&wdev->dev); > + if (bkbd >= 0) > + yb9_kbdock_report_locked(bkbd, &wdev->dev); > + } > + mutex_unlock(&yb9.lock); > + > + return 0; > +} > + > +static void yb9_kbdock_event_remove(struct wmi_device *wdev) > +{ > + mutex_lock(&yb9.lock); guard() > + yb9.input_dev = NULL; > + mutex_unlock(&yb9.lock); > +} > + > +static int yb9_kbdock_resume(struct device *dev) > +{ > + int bkbd; > + > + mutex_lock(&yb9.lock); > + if (yb9.input_dev && yb9.block_wdev) { > + bkbd = yb9_kbdock_query_locked(dev); > + if (bkbd >= 0) > + yb9_kbdock_report_locked(bkbd, dev); This looks mostly duplicated with the code in yb9_kbdock_event_probe(), try to consolidate somehow. > + } > + mutex_unlock(&yb9.lock); > + return 0; > +} > + > +static DEFINE_SIMPLE_DEV_PM_OPS(yb9_kbdock_pm_ops, NULL, yb9_kbdock_resume); > + > +static const struct wmi_device_id yb9_kbdock_event_id_table[] = { > + { .guid_string = YB9_KBDOCK_EVENT_GUID }, > + { } > +}; > +MODULE_DEVICE_TABLE(wmi, yb9_kbdock_event_id_table); > + > +static struct wmi_driver yb9_kbdock_event_driver = { > + .driver = { > + .name = "lenovo-yb9-kbdock", > + .dev_groups = yb9_kbdock_groups, > + .pm = pm_sleep_ptr(&yb9_kbdock_pm_ops), > + }, > + .id_table = yb9_kbdock_event_id_table, > + .no_singleton = true, > + .probe = yb9_kbdock_event_probe, > + .remove = yb9_kbdock_event_remove, > + .notify = yb9_kbdock_notify, > +}; > + > +/* ------------------------------------------------------------------ > + * Block WMI driver — LENOVO_FEATURE_STATUS_DATA > + * ------------------------------------------------------------------ */ > + > +static int yb9_kbdock_block_probe(struct wmi_device *wdev, const void *ctx) > +{ > + int bkbd; > + > + if (!dmi_check_system(yb9_kbdock_dmi_table)) > + return -ENODEV; > + > + mutex_lock(&yb9.lock); > + yb9.block_wdev = wdev; > + /* Read initial state if the event device has already probed. */ > + if (yb9.input_dev) { > + bkbd = yb9_kbdock_query_locked(&wdev->dev); > + if (bkbd >= 0) > + yb9_kbdock_report_locked(bkbd, &wdev->dev); > + } > + mutex_unlock(&yb9.lock); More duplication? > + return 0; > +} > + > +static void yb9_kbdock_block_remove(struct wmi_device *wdev) > +{ > + mutex_lock(&yb9.lock); guard() > + yb9.block_wdev = NULL; > + mutex_unlock(&yb9.lock); > +} > + > +static const struct wmi_device_id yb9_kbdock_block_id_table[] = { > + { .guid_string = YB9_KBDOCK_QUERY_GUID }, > + { } > +}; > + > +static struct wmi_driver yb9_kbdock_block_driver = { > + .driver = { > + .name = "lenovo-yb9-kbdock-block", > + }, > + .id_table = yb9_kbdock_block_id_table, > + .no_singleton = true, > + .probe = yb9_kbdock_block_probe, > + .remove = yb9_kbdock_block_remove, > +}; > + > +/* ------------------------------------------------------------------ > + * Module init / exit > + * ------------------------------------------------------------------ */ > + > +static int __init yb9_kbdock_init(void) > +{ > + int ret; > + > + mutex_init(&yb9.lock); > + > + ret = wmi_driver_register(&yb9_kbdock_event_driver); > + if (ret) > + return ret; > + > + ret = wmi_driver_register(&yb9_kbdock_block_driver); > + if (ret) { > + wmi_driver_unregister(&yb9_kbdock_event_driver); > + return ret; > + } > + return 0; > +} > +module_init(yb9_kbdock_init); > + > +static void __exit yb9_kbdock_exit(void) > +{ > + wmi_driver_unregister(&yb9_kbdock_block_driver); > + wmi_driver_unregister(&yb9_kbdock_event_driver); > +} > +module_exit(yb9_kbdock_exit); > + > +MODULE_AUTHOR("Dave Carey "); > +MODULE_DESCRIPTION("Lenovo Yoga Book 9 keyboard dock detection"); > +MODULE_LICENSE("GPL"); > -- > 2.54.0 > -- i.