* Re: [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver
2026-06-10 15:53 ` [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver Dave Carey
@ 2026-06-10 16:40 ` Hans de Goede
2026-06-10 17:59 ` Armin Wolf
1 sibling, 0 replies; 6+ messages in thread
From: Hans de Goede @ 2026-06-10 16:40 UTC (permalink / raw)
To: Dave Carey, platform-driver-x86; +Cc: ilpo.jarvinen
Hi,
On 10-Jun-26 17:53, 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 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_query_block() 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.
>
Acked-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
> Signed-off-by: Dave Carey <carvsdriver@gmail.com>
Regards,
Hans
> ---
> v8:
> - Add #include <linux/bits.h> (required for GENMASK).
> - Add #include <linux/dev_printk.h> (explicit include for dev_warn/dev_dbg).
> - Use __MUTEX_INITIALIZER(yb9.lock) for static mutex initialization; removes
> mutex_init() call and the need for mutex_destroy().
> - Update wmidev_query_block() call to pass min_size=8; remove manual length
> check that is now handled by the WMI core.
> - Move u8 *data __free(kfree) declaration to immediately after the successful
> wmidev_query_block() call (cleanup.h convention).
> - Change data type from void * to u8 * to allow pointer arithmetic without cast.
> - Remove (int) cast from FIELD_GET() return value.
> - Remove blank line between yb9_kbdock_query_locked() call and error check in
> keyboard_position_show().
> - Use %d format specifier in sysfs_emit(); remove (unsigned int) cast.
>
> v7:
> - Use wmidev_query_block() in place of deprecated wmidev_block_query().
> Use __free(kfree) to manage the output buffer; simplify the parsing
> to a single length check now that the WMI core handles type conversion.
> - Define BKBD_FIELD with GENMASK() and extract the field with FIELD_GET()
> instead of open-coded masking.
> - Use guard(mutex) for all lock/unlock pairs.
> - Add yb9_kbdock_sync_locked() helper to consolidate the duplicated
> initial-state read pattern in event_probe, block_probe, and resume.
> - Add linux/bitfield.h, linux/cleanup.h, linux/slab.h includes.
> - Fix comment on struct mutex field; use Context:/Returns: sections in
> the kerneldoc comment for yb9_kbdock_query_locked().
>
> 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 | 312 ++++++++++++++++++
> 5 files changed, 353 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/<guid>/keyboard_position
> +Date: April 2026
> +KernelVersion: 6.10
> +Contact: Dave Carey <carvsdriver@gmail.com>
> +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 <carvsdriver@gmail.com>
> +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 <hansg@kernel.org>
> 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..f00e5d4
> --- /dev/null
> +++ b/drivers/platform/x86/lenovo/yb9-kbdock.c
> @@ -0,0 +1,312 @@
> +// 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 <carvsdriver@gmail.com>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/cleanup.h>
> +#include <linux/dev_printk.h>
> +#include <linux/dmi.h>
> +#include <linux/input.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pm.h>
> +#include <linux/slab.h>
> +#include <linux/wmi.h>
> +
> +#define YB9_KBDOCK_EVENT_GUID "806BD2A2-177B-481D-BFB5-3BA0BB4A2285"
> +#define YB9_KBDOCK_QUERY_GUID "E7F300FA-21CD-4003-ADAC-2696135982E6"
> +
> +/* 2-bit EC field encoding the keyboard dock position */
> +#define BKBD_FIELD GENMASK(1, 0)
> +
> +/* 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; /* protects input_dev and block_wdev */
> + struct input_dev *input_dev; /* set by event probe */
> + struct wmi_device *block_wdev; /* set by block probe */
> +} yb9 = {
> + .lock = __MUTEX_INITIALIZER(yb9.lock),
> +};
> +
> +/**
> + * yb9_kbdock_query_locked() - Read BKBD from the block device.
> + * @log_dev: Device for logging.
> + *
> + * Context: Caller must hold yb9.lock.
> + * Returns: 0-3 on success, -errno on failure.
> + */
> +static int yb9_kbdock_query_locked(struct device *log_dev)
> +{
> + struct wmi_buffer out = {};
> + u32 bkbd;
> + int ret;
> +
> + if (!yb9.block_wdev)
> + return -ENODEV;
> +
> + ret = wmidev_query_block(yb9.block_wdev, 0, &out, 8);
> + if (ret) {
> + dev_warn(log_dev, "WQAF failed: %d\n", ret);
> + return ret;
> + }
> +
> + u8 *data __free(kfree) = out.data;
> +
> + /*
> + * LENOVO_FEATURE_STATUS_DATA: 8-byte buffer {IDs=0x00060000, Status=BKBD}.
> + * BKBD is at bytes 4-7.
> + */
> + memcpy(&bkbd, data + 4, sizeof(bkbd));
> + return FIELD_GET(BKBD_FIELD, 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);
> +}
> +
> +/* Read BKBD and report if both WMI devices are ready. Caller must hold yb9.lock. */
> +static void yb9_kbdock_sync_locked(struct device *log_dev)
> +{
> + int bkbd;
> +
> + if (!yb9.input_dev || !yb9.block_wdev)
> + return;
> +
> + bkbd = yb9_kbdock_query_locked(log_dev);
> + if (bkbd >= 0)
> + yb9_kbdock_report_locked(bkbd, log_dev);
> +}
> +
> +/* ------------------------------------------------------------------
> + * sysfs
> + * ------------------------------------------------------------------ */
> +
> +static ssize_t keyboard_position_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int bkbd;
> +
> + guard(mutex)(&yb9.lock);
> + bkbd = yb9_kbdock_query_locked(dev);
> + if (bkbd < 0)
> + return bkbd;
> + return sysfs_emit(buf, "%d\n", 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 = FIELD_GET(BKBD_FIELD, data->integer.value);
> +
> + guard(mutex)(&yb9.lock);
> + if (yb9.input_dev)
> + yb9_kbdock_report_locked(bkbd, &wdev->dev);
> +}
> +
> +static int yb9_kbdock_event_probe(struct wmi_device *wdev, const void *ctx)
> +{
> + struct input_dev *input_dev;
> + int 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;
> +
> + guard(mutex)(&yb9.lock);
> + yb9.input_dev = input_dev;
> + yb9_kbdock_sync_locked(&wdev->dev);
> + return 0;
> +}
> +
> +static void yb9_kbdock_event_remove(struct wmi_device *wdev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9.input_dev = NULL;
> +}
> +
> +static int yb9_kbdock_resume(struct device *dev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9_kbdock_sync_locked(dev);
> + 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)
> +{
> + if (!dmi_check_system(yb9_kbdock_dmi_table))
> + return -ENODEV;
> +
> + guard(mutex)(&yb9.lock);
> + yb9.block_wdev = wdev;
> + yb9_kbdock_sync_locked(&wdev->dev);
> + return 0;
> +}
> +
> +static void yb9_kbdock_block_remove(struct wmi_device *wdev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9.block_wdev = NULL;
> +}
> +
> +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;
> +
> + 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 <carvsdriver@gmail.com>");
> +MODULE_DESCRIPTION("Lenovo Yoga Book 9 keyboard dock detection");
> +MODULE_LICENSE("GPL");
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver
2026-06-10 15:53 ` [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver Dave Carey
2026-06-10 16:40 ` Hans de Goede
@ 2026-06-10 17:59 ` Armin Wolf
1 sibling, 0 replies; 6+ messages in thread
From: Armin Wolf @ 2026-06-10 17:59 UTC (permalink / raw)
To: Dave Carey, platform-driver-x86; +Cc: ilpo.jarvinen, hansg
Am 10.06.26 um 17:53 schrieb Dave Carey:
> 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 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.cd 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.
Hi,
how many instances of the LENOVO_FEATURE_STATUS_DATA data block exist?
You can check this with the lswmi tool (https://pypi.org/project/lswmi/).
>
> 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_query_block() 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 <carvsdriver@gmail.com>
> ---
> v8:
> - Add #include <linux/bits.h> (required for GENMASK).
> - Add #include <linux/dev_printk.h> (explicit include for dev_warn/dev_dbg).
> - Use __MUTEX_INITIALIZER(yb9.lock) for static mutex initialization; removes
> mutex_init() call and the need for mutex_destroy().
> - Update wmidev_query_block() call to pass min_size=8; remove manual length
> check that is now handled by the WMI core.
> - Move u8 *data __free(kfree) declaration to immediately after the successful
> wmidev_query_block() call (cleanup.h convention).
> - Change data type from void * to u8 * to allow pointer arithmetic without cast.
> - Remove (int) cast from FIELD_GET() return value.
> - Remove blank line between yb9_kbdock_query_locked() call and error check in
> keyboard_position_show().
> - Use %d format specifier in sysfs_emit(); remove (unsigned int) cast.
>
> v7:
> - Use wmidev_query_block() in place of deprecated wmidev_block_query().
> Use __free(kfree) to manage the output buffer; simplify the parsing
> to a single length check now that the WMI core handles type conversion.
> - Define BKBD_FIELD with GENMASK() and extract the field with FIELD_GET()
> instead of open-coded masking.
> - Use guard(mutex) for all lock/unlock pairs.
> - Add yb9_kbdock_sync_locked() helper to consolidate the duplicated
> initial-state read pattern in event_probe, block_probe, and resume.
> - Add linux/bitfield.h, linux/cleanup.h, linux/slab.h includes.
> - Fix comment on struct mutex field; use Context:/Returns: sections in
> the kerneldoc comment for yb9_kbdock_query_locked().
>
> 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 | 312 ++++++++++++++++++
> 5 files changed, 353 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/<guid>/keyboard_position
> +Date: April 2026
> +KernelVersion: 6.10
> +Contact: Dave Carey <carvsdriver@gmail.com>
> +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 <carvsdriver@gmail.com>
> +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 <hansg@kernel.org>
> 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..f00e5d4
> --- /dev/null
> +++ b/drivers/platform/x86/lenovo/yb9-kbdock.c
> @@ -0,0 +1,312 @@
> +// 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 <carvsdriver@gmail.com>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/cleanup.h>
> +#include <linux/dev_printk.h>
> +#include <linux/dmi.h>
> +#include <linux/input.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pm.h>
> +#include <linux/slab.h>
> +#include <linux/wmi.h>
> +
> +#define YB9_KBDOCK_EVENT_GUID "806BD2A2-177B-481D-BFB5-3BA0BB4A2285"
> +#define YB9_KBDOCK_QUERY_GUID "E7F300FA-21CD-4003-ADAC-2696135982E6"
> +
> +/* 2-bit EC field encoding the keyboard dock position */
> +#define BKBD_FIELD GENMASK(1, 0)
> +
> +/* 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; /* protects input_dev and block_wdev */
> + struct input_dev *input_dev; /* set by event probe */
> + struct wmi_device *block_wdev; /* set by block probe */
> +} yb9 = {
> + .lock = __MUTEX_INITIALIZER(yb9.lock),
> +};
Nack, having global data like this is not a good idea. Please use a notifier like uniwill-wmi.c
to deliver WMI events to the WMI block driver, and put the input device into the private data struct
of said driver.
This would also allow you to get rid of the mutex.
> +
> +/**
> + * yb9_kbdock_query_locked() - Read BKBD from the block device.
> + * @log_dev: Device for logging.
> + *
> + * Context: Caller must hold yb9.lock.
> + * Returns: 0-3 on success, -errno on failure.
> + */
> +static int yb9_kbdock_query_locked(struct device *log_dev)
> +{
> + struct wmi_buffer out = {};
> + u32 bkbd;
> + int ret;
> +
> + if (!yb9.block_wdev)
> + return -ENODEV;
> +
> + ret = wmidev_query_block(yb9.block_wdev, 0, &out, 8);
Please define a struct like this:
struct lenovo_feature_status {
__le32 id;
__le32 status;
} __packed;
You should then use said struct for size calculations using sizeof()
and for accessing the individual fields using le32_to_cpu().
> + if (ret) {
> + dev_warn(log_dev, "WQAF failed: %d\n", ret);
Please drop the error message, passing on the error code should be enough.
> + return ret;
> + }
> +
> + u8 *data __free(kfree) = out.data;
> +
> + /*
> + * LENOVO_FEATURE_STATUS_DATA: 8-byte buffer {IDs=0x00060000, Status=BKBD}.
> + * BKBD is at bytes 4-7.
> + */
> + memcpy(&bkbd, data + 4, sizeof(bkbd));
> + return FIELD_GET(BKBD_FIELD, bkbd);
I think the whole 32-bit status field is meant to be used instead of only the first 2 bits.
Can you share the output of "acpidump" on this machine so i can take a look myself?
IMHO we should verify here that the ID value is correct.
> +}
> +
> +/* 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);
> +}
> +
> +/* Read BKBD and report if both WMI devices are ready. Caller must hold yb9.lock. */
> +static void yb9_kbdock_sync_locked(struct device *log_dev)
> +{
> + int bkbd;
> +
> + if (!yb9.input_dev || !yb9.block_wdev)
> + return;
> +
> + bkbd = yb9_kbdock_query_locked(log_dev);
> + if (bkbd >= 0)
> + yb9_kbdock_report_locked(bkbd, log_dev);
> +}
> +
> +/* ------------------------------------------------------------------
> + * sysfs
> + * ------------------------------------------------------------------ */
> +
> +static ssize_t keyboard_position_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int bkbd;
> +
> + guard(mutex)(&yb9.lock);
> + bkbd = yb9_kbdock_query_locked(dev);
> + if (bkbd < 0)
> + return bkbd;
> + return sysfs_emit(buf, "%d\n", bkbd);
> +}
> +static DEVICE_ATTR_RO(keyboard_position);
Please mark this attribute as const. The same should be done with yb9_kbdock_attrs[].
> +
> +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 = FIELD_GET(BKBD_FIELD, data->integer.value);
> +
> + guard(mutex)(&yb9.lock);
> + if (yb9.input_dev)
> + yb9_kbdock_report_locked(bkbd, &wdev->dev);
Please use .notify_new() instead of .notify() to avoid having to deal with ACPI objects.
> +}
> +
> +static int yb9_kbdock_event_probe(struct wmi_device *wdev, const void *ctx)
> +{
> + struct input_dev *input_dev;
> + int 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;
> +
> + guard(mutex)(&yb9.lock);
> + yb9.input_dev = input_dev;
> + yb9_kbdock_sync_locked(&wdev->dev);
> + return 0;
> +}
> +
> +static void yb9_kbdock_event_remove(struct wmi_device *wdev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9.input_dev = NULL;
> +}
> +
> +static int yb9_kbdock_resume(struct device *dev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9_kbdock_sync_locked(dev);
> + 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)
> +{
> + if (!dmi_check_system(yb9_kbdock_dmi_table))
> + return -ENODEV;
> +
> + guard(mutex)(&yb9.lock);
> + yb9.block_wdev = wdev;
> + yb9_kbdock_sync_locked(&wdev->dev);
> + return 0;
> +}
> +
> +static void yb9_kbdock_block_remove(struct wmi_device *wdev)
> +{
> + guard(mutex)(&yb9.lock);
> + yb9.block_wdev = NULL;
> +}
> +
> +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;
I think you should do the DMI check here. This would allow you to mark the DMI whitelist
as __initconst.
Thanks,
Armin Wolf
> +
> + 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 <carvsdriver@gmail.com>");
> +MODULE_DESCRIPTION("Lenovo Yoga Book 9 keyboard dock detection");
> +MODULE_LICENSE("GPL");
^ permalink raw reply [flat|nested] 6+ messages in thread