[PATCH v8 0/2] platform/x86/lenovo: Yoga Book 9 keyboard dock detection

[PATCH v8 0/2] platform/x86/lenovo: Yoga Book 9 keyboard dock detection

[Dave Carey]

Hi Ilpo,

Thank you for the v7 review.  All nine items are addressed in v8.

One item needs a brief explanation: for the mutex lifecycle, I used
__MUTEX_INITIALIZER(yb9.lock) in the struct definition rather than
devm_mutex_init().  The yb9 struct is a module-level global with no
associated device at __init time, and since yb9_kbdock_block_probe()
acquires the lock and can run before yb9_kbdock_event_probe(), the
mutex must be valid before either probe runs.  Static initialization
achieves the same goal (no manual init/destroy lifecycle) without
requiring a device pointer.  If you'd prefer a different approach,
please let me know.

Changes in 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 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.

Patch 1/2 (lenovo-ymc) is unchanged from v7.

Tested on Lenovo Yoga Book 9 14IAH10 (model 83KJ), kernel 7.0.

Dave Carey (2):
  platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10
  platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

 .../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 ++++++++++++++++++
 drivers/platform/x86/lenovo/ymc.c              |  19 ++
 6 files changed, 372 insertions(+)

--
2.54.0

[PATCH v8 1/2] platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10

[Dave Carey]

The Yoga Book 9 14IAH10 (DMI product name "83KJ") has a dedicated
yb9-kbdock WMI driver that registers an input device reporting
SW_TABLET_MODE to track the detachable Bluetooth keyboard.

lenovo-ymc also loads on this machine and creates an input node with the
SW_TABLET_MODE capability bit set.  For input switches, the presence of
the capability bit has semantic meaning: userspace (e.g. GNOME) reads
the switch state at startup from every node advertising the capability
and does not expect more than one such node.

Add a DMI match for the Yoga Book 9 14IAH10 to probe() so that
lenovo-ymc returns -ENODEV on this hardware, leaving yb9-kbdock as the
sole SW_TABLET_MODE source.  The ymc_ec_trigger EC write, the only
other action taken in response to a YMC event, is guarded by a separate
DMI table that excludes this machine; no other functionality is affected.

Signed-off-by: Dave Carey <carvsdriver@gmail.com>
---
 drivers/platform/x86/lenovo/ymc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/platform/x86/lenovo/ymc.c b/drivers/platform/x86/lenovo/ymc.c
--- a/drivers/platform/x86/lenovo/ymc.c
+++ b/drivers/platform/x86/lenovo/ymc.c
@@ -23,7 +23,23 @@ module_param(force, bool, 0444);
 static bool force;
 module_param(force, bool, 0444);
 MODULE_PARM_DESC(force, "Force loading on boards without a convertible DMI chassis-type");

+static const struct dmi_system_id lenovo_ymc_nosupport_dmi_table[] = {
+	{
+		/*
+		 * Yoga Book 9 14IAH10: SW_TABLET_MODE is reported by the
+		 * yb9-kbdock driver.  Suppress lenovo-ymc on this machine to
+		 * avoid userspace seeing two input nodes that both advertise
+		 * the SW_TABLET_MODE capability.
+		 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"),
+		},
+	},
+	{ }
+};
+
 static const struct dmi_system_id allowed_chasis_types_dmi_table[] = {
 	{
 		.matches = {
@@ -100,7 +116,10 @@ static int lenovo_ymc_probe(struct wmi_device *wdev, const void *ctx)
 	struct lenovo_ymc_private *priv;
 	struct input_dev *input_dev;
 	int err;

+	if (dmi_check_system(lenovo_ymc_nosupport_dmi_table))
+		return -ENODEV;
+
 	if (!dmi_check_system(allowed_chasis_types_dmi_table)) {
 		if (force)
 			dev_info(&wdev->dev, "Force loading Lenovo YMC support\n");
--
2.54.0

Re: [PATCH v8 1/2] platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10

[Hans de Goede]

Hi Dave,

On 10-Jun-26 17:53, Dave Carey wrote:
> The Yoga Book 9 14IAH10 (DMI product name "83KJ") has a dedicated
> yb9-kbdock WMI driver that registers an input device reporting
> SW_TABLET_MODE to track the detachable Bluetooth keyboard.
> 
> lenovo-ymc also loads on this machine and creates an input node with the
> SW_TABLET_MODE capability bit set.  For input switches, the presence of
> the capability bit has semantic meaning: userspace (e.g. GNOME) reads
> the switch state at startup from every node advertising the capability
> and does not expect more than one such node.
> 
> Add a DMI match for the Yoga Book 9 14IAH10 to probe() so that
> lenovo-ymc returns -ENODEV on this hardware, leaving yb9-kbdock as the
> sole SW_TABLET_MODE source.  The ymc_ec_trigger EC write, the only
> other action taken in response to a YMC event, is guarded by a separate
> DMI table that excludes this machine; no other functionality is affected.
> 

You dropped my tags again, if there is going to be a v9 please
add:

Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>

here, so just above your Signed-off-by.

> Signed-off-by: Dave Carey <carvsdriver@gmail.com>



Regards,

Hans





> ---
>  drivers/platform/x86/lenovo/ymc.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/platform/x86/lenovo/ymc.c b/drivers/platform/x86/lenovo/ymc.c
> --- a/drivers/platform/x86/lenovo/ymc.c
> +++ b/drivers/platform/x86/lenovo/ymc.c
> @@ -23,7 +23,23 @@ module_param(force, bool, 0444);
>  static bool force;
>  module_param(force, bool, 0444);
>  MODULE_PARM_DESC(force, "Force loading on boards without a convertible DMI chassis-type");
> 
> +static const struct dmi_system_id lenovo_ymc_nosupport_dmi_table[] = {
> +	{
> +		/*
> +		 * Yoga Book 9 14IAH10: SW_TABLET_MODE is reported by the
> +		 * yb9-kbdock driver.  Suppress lenovo-ymc on this machine to
> +		 * avoid userspace seeing two input nodes that both advertise
> +		 * the SW_TABLET_MODE capability.
> +		 */
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"),
> +		},
> +	},
> +	{ }
> +};
> +
>  static const struct dmi_system_id allowed_chasis_types_dmi_table[] = {
>  	{
>  		.matches = {
> @@ -100,7 +116,10 @@ static int lenovo_ymc_probe(struct wmi_device *wdev, const void *ctx)
>  	struct lenovo_ymc_private *priv;
>  	struct input_dev *input_dev;
>  	int err;
> 
> +	if (dmi_check_system(lenovo_ymc_nosupport_dmi_table))
> +		return -ENODEV;
> +
>  	if (!dmi_check_system(allowed_chasis_types_dmi_table)) {
>  		if (force)
>  			dev_info(&wdev->dev, "Force loading Lenovo YMC support\n");
> --
> 2.54.0

[PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

[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.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.

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),
+};
+
+/**
+ * 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");
-- 
2.54.0

Re: [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

[Hans de Goede]

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");

Re: [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

[Armin Wolf]

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");

Re: [PATCH v8 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

[Dave Carey]

On Wed, 10 Jun 2026 19:59:53 +0200, Armin Wolf wrote:
> 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/).

One instance:

  E7F300FA-21CD-4003-ADAC-2696135982E6: Data   (Instances: 1)

> 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().

Understood, will do.

> Please drop the error message, passing on the error code should be enough.

Will do.

> 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.

The DSDT confirms the field layout.  In the EC namespace, BKBD is
declared as a 2-bit field:

  Offset (0x23),
      ,   2,
  PELF,   1,
      ,   1,
  BKBD,   2,     /* bits 4-5 of EC byte 0x23 */
      ,   1,
  U7U9,   1,

WQAF builds an 8-byte buffer and assigns EC0.BKBD to a 32-bit dword:

  Name (LFSD, Buffer (0x08) { 0x00 })
  CreateDWordField (LFSD, Zero, LFID)
  CreateDWordField (LFSD, 0x04, LFST)
  LFID = 0x00060000
  If ((Acquire (EC0.LFCM, 0xA000) == Zero)) {
      LFST = EC0.BKBD
      Release (EC0.LFCM)
  }
  Return (LFSD)

ACPI zero-extends the 2-bit BKBD value to 32 bits, so le32_to_cpu(fs->status)
is always 0-3 and equals the full BKBD encoding.  I'll use the status field
directly and add an ID check (le32_to_cpu(fs->id) == 0x00060000) as you
suggest.

_WED(0xEB) also reads EC0.BKBD directly and returns it as an integer,
which is consistent.

I can provide the full acpidump if it would be useful; let me know.

> 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.

Understood.  I'll restructure along the lines of uniwill-wmi.c:

  - Event driver (LENOVO_BTKBD_EVENT) owns a BLOCKING_NOTIFIER_HEAD and
    fires it from its notify callback.  It exports
    devm_yb9_kbdock_register_notifier() for consumers.

  - Block driver (LENOVO_FEATURE_STATUS_DATA) owns the input_dev in its
    driver private data, registers a notifier_block at probe time, reads
    initial state via wmidev_query_block() on itself, and handles sysfs
    and PM resume.

No global struct, no mutex.

> Please mark this attribute as const.  The same should be done with
> yb9_kbdock_attrs[].

Will do.

> Please use .notify_new() instead of .notify() to avoid having to deal
> with ACPI objects.

Will do.  notify_new receives a const struct wmi_buffer *, which is
cleaner for extracting the integer.

> I think you should do the DMI check here.  This would allow you to mark
> the DMI whitelist as __initconst.

Good point.  I'll move dmi_check_system() into yb9_kbdock_init() and
mark the table __initconst.

Thanks,
Dave

[PATCH v9 0/2] platform/x86/lenovo: Yoga Book 9 keyboard dock detection

[Dave Carey]

Hi Armin,

Thank you for the v8 review.  All nine items are addressed in v9:

  - Added struct lenovo_feature_status { __le32 id; __le32 status; } __packed;
    and used it for size calculations and field access via le32_to_cpu().
  - Added ID verification: return -EIO if le32_to_cpu(fs->id) != 0x00060000.
  - Dropped the error message from yb9_kbdock_query(); returning the error
    code is sufficient.
  - Replaced the global struct + mutex with a BLOCKING_NOTIFIER_HEAD at
    module scope.  The event driver fires the chain from .notify_new(); the
    block driver registers a notifier_block and owns the input_dev in its
    per-device private struct.  No global state, no mutex.
  - Switched from .notify() to .notify_new() to receive a pre-parsed
    wmi_buffer directly.
  - Marked yb9_kbdock_attrs[] and the attribute pointer as const.
  - Moved dmi_check_system() to yb9_kbdock_init(); DMI table is now
    __initconst.
  - Used le32_to_cpu(fs->status) directly (BKBD is zero-extended to 32 bits
    by ACPI); removed BKBD_FIELD masking and the BKBD_TOP_HALF /
    BKBD_BOTTOM_HALF constants (not needed by driver logic).
  - Dropped #include <linux/bitfield.h>, <linux/bits.h>, and <linux/mutex.h>
    (no longer needed); added #include <linux/notifier.h>.

Patch 1/2 (lenovo-ymc) is unchanged from v8, with Hans de Goede's
Reviewed-by tag added.

Tested on Lenovo Yoga Book 9 14IAH10 (model 83KJ), kernel 7.0.

Dave Carey (2):
  platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10
  platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

 Documentation/ABI/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                  | 310 ++++++++++++++++++
 drivers/platform/x86/lenovo/ymc.c                         |  19 ++
 6 files changed, 370 insertions(+)

--
2.54.0

[PATCH v9 1/2] platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10

[Dave Carey]

The Yoga Book 9 14IAH10 (DMI product name "83KJ") has a dedicated
yb9-kbdock WMI driver that registers an input device reporting
SW_TABLET_MODE to track the detachable Bluetooth keyboard.

lenovo-ymc also loads on this machine and creates an input node with the
SW_TABLET_MODE capability bit set.  For input switches, the presence of
the capability bit has semantic meaning: userspace (e.g. GNOME) reads
the switch state at startup from every node advertising the capability
and does not expect more than one such node.

Add a DMI match for the Yoga Book 9 14IAH10 to probe() so that
lenovo-ymc returns -ENODEV on this hardware, leaving yb9-kbdock as the
sole SW_TABLET_MODE source.  The ymc_ec_trigger EC write, the only
other action taken in response to a YMC event, is guarded by a separate
DMI table that excludes this machine; no other functionality is affected.

Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Dave Carey <carvsdriver@gmail.com>
---
 drivers/platform/x86/lenovo/ymc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/platform/x86/lenovo/ymc.c b/drivers/platform/x86/lenovo/ymc.c
--- a/drivers/platform/x86/lenovo/ymc.c
+++ b/drivers/platform/x86/lenovo/ymc.c
@@ -23,7 +23,23 @@ module_param(force, bool, 0444);
 static bool force;
 module_param(force, bool, 0444);
 MODULE_PARM_DESC(force, "Force loading on boards without a convertible DMI chassis-type");

+static const struct dmi_system_id lenovo_ymc_nosupport_dmi_table[] = {
+	{
+		/*
+		 * Yoga Book 9 14IAH10: SW_TABLET_MODE is reported by the
+		 * yb9-kbdock driver.  Suppress lenovo-ymc on this machine to
+		 * avoid userspace seeing two input nodes that both advertise
+		 * the SW_TABLET_MODE capability.
+		 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"),
+		},
+	},
+	{ }
+};
+
 static const struct dmi_system_id allowed_chasis_types_dmi_table[] = {
 	{
 		.matches = {
@@ -100,7 +116,10 @@ static int lenovo_ymc_probe(struct wmi_device *wdev, const void *ctx)
 	struct lenovo_ymc_private *priv;
 	struct input_dev *input_dev;
 	int err;

+	if (dmi_check_system(lenovo_ymc_nosupport_dmi_table))
+		return -ENODEV;
+
 	if (!dmi_check_system(allowed_chasis_types_dmi_table)) {
 		if (force)
 			dev_info(&wdev->dev, "Force loading Lenovo YMC support\n");
--
2.54.0

[PATCH v9 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

[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.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 sharing a module-level
BLOCKING_NOTIFIER_HEAD:

  - The event driver (LENOVO_BTKBD_EVENT) uses .notify_new() to receive
    a pre-parsed wmi_buffer and fires the notifier chain with the BKBD
    value extracted from the buffer.

  - The block driver (LENOVO_FEATURE_STATUS_DATA) owns the input_dev in
    its per-device private struct.  At probe time it registers a
    notifier_block on the chain and reads the initial BKBD state via
    wmidev_query_block().  The WMI buffer is parsed as
    struct lenovo_feature_status { __le32 id; __le32 status; }, and the
    ID field is verified before the status is used.

  - 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 read-only sysfs attribute
    "keyboard_position".

  - BKBD state is re-read via wmidev_query_block() 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>
---
 .../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      | 310 ++++++++++++++++++
 5 files changed, 351 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..dbf7ff4
--- /dev/null
+++ b/drivers/platform/x86/lenovo/yb9-kbdock.c
@@ -0,0 +1,310 @@
+// 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.
+ *
+ * The event driver (LENOVO_BTKBD_EVENT) fires a notifier chain on each WMI
+ * event.  The block driver (LENOVO_FEATURE_STATUS_DATA) owns the input_dev
+ * and registers a notifier_block to receive those events, eliminating the
+ * need for shared global state or a mutex.
+ *
+ * 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/cleanup.h>
+#include <linux/dev_printk.h>
+#include <linux/dmi.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/notifier.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"
+
+/* BKBD encoding */
+#define BKBD_DETACHED		0
+
+/* LENOVO_FEATURE_STATUS_DATA feature selector */
+#define YB9_FEATURE_STATUS_ID	0x00060000u
+
+/*
+ * LENOVO_FEATURE_STATUS_DATA: 8-byte buffer {uint32 IDs, uint32 Status}.
+ * IDs is always 0x00060000; Status holds the BKBD value (0–3).
+ */
+struct lenovo_feature_status {
+	__le32 id;
+	__le32 status;
+} __packed;
+
+/* ------------------------------------------------------------------
+ * Notifier chain — event driver fires it, block driver listens
+ * ------------------------------------------------------------------ */
+
+static BLOCKING_NOTIFIER_HEAD(yb9_kbdock_chain_head);
+
+static void devm_yb9_kbdock_unregister_notifier(void *data)
+{
+	struct notifier_block *nb = data;
+
+	blocking_notifier_chain_unregister(&yb9_kbdock_chain_head, nb);
+}
+
+static int devm_yb9_kbdock_register_notifier(struct device *dev,
+					      struct notifier_block *nb)
+{
+	int ret;
+
+	ret = blocking_notifier_chain_register(&yb9_kbdock_chain_head, nb);
+	if (ret < 0)
+		return ret;
+
+	return devm_add_action_or_reset(dev, devm_yb9_kbdock_unregister_notifier, nb);
+}
+
+/* ------------------------------------------------------------------
+ * Block WMI driver — LENOVO_FEATURE_STATUS_DATA
+ * (owns input_dev, sysfs, PM resume)
+ * ------------------------------------------------------------------ */
+
+struct yb9_kbdock_data {
+	struct wmi_device	*wdev;
+	struct input_dev	*input_dev;
+	struct notifier_block	 nb;
+};
+
+static int yb9_kbdock_query(struct yb9_kbdock_data *d)
+{
+	struct wmi_buffer out = {};
+	int ret;
+
+	ret = wmidev_query_block(d->wdev, 0, &out,
+				 sizeof(struct lenovo_feature_status));
+	if (ret)
+		return ret;
+
+	struct lenovo_feature_status *fs __free(kfree) = out.data;
+
+	if (le32_to_cpu(fs->id) != YB9_FEATURE_STATUS_ID)
+		return -EIO;
+
+	return le32_to_cpu(fs->status);
+}
+
+static void yb9_kbdock_report(struct yb9_kbdock_data *d, u32 bkbd)
+{
+	int tablet = (bkbd == BKBD_DETACHED) ? 1 : 0;
+
+	input_report_switch(d->input_dev, SW_TABLET_MODE, tablet);
+	input_sync(d->input_dev);
+	dev_dbg(&d->wdev->dev, "BKBD=%u SW_TABLET_MODE=%d\n", bkbd, tablet);
+}
+
+static void yb9_kbdock_sync(struct yb9_kbdock_data *d)
+{
+	int bkbd = yb9_kbdock_query(d);
+
+	if (bkbd >= 0)
+		yb9_kbdock_report(d, bkbd);
+}
+
+static int yb9_kbdock_nb_call(struct notifier_block *nb,
+			       unsigned long bkbd, void *unused)
+{
+	struct yb9_kbdock_data *d =
+		container_of(nb, struct yb9_kbdock_data, nb);
+
+	yb9_kbdock_report(d, bkbd);
+	return NOTIFY_DONE;
+}
+
+static ssize_t keyboard_position_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct yb9_kbdock_data *d = dev_get_drvdata(dev);
+	int bkbd = yb9_kbdock_query(d);
+
+	if (bkbd < 0)
+		return bkbd;
+	return sysfs_emit(buf, "%d\n", bkbd);
+}
+static DEVICE_ATTR_RO(keyboard_position);
+
+static const struct attribute * const yb9_kbdock_attrs[] = {
+	&dev_attr_keyboard_position.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(yb9_kbdock);
+
+static int yb9_kbdock_resume(struct device *dev)
+{
+	struct yb9_kbdock_data *d = dev_get_drvdata(dev);
+
+	yb9_kbdock_sync(d);
+	return 0;
+}
+static DEFINE_SIMPLE_DEV_PM_OPS(yb9_kbdock_pm_ops, NULL, yb9_kbdock_resume);
+
+static int yb9_kbdock_block_probe(struct wmi_device *wdev, const void *ctx)
+{
+	struct yb9_kbdock_data *d;
+	struct input_dev *input_dev;
+	int ret;
+
+	d = devm_kzalloc(&wdev->dev, sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	d->wdev = wdev;
+
+	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_QUERY_GUID "/input0";
+	input_dev->id.bustype	= BUS_HOST;
+	input_set_capability(input_dev, EV_SW, SW_TABLET_MODE);
+
+	ret = input_register_device(input_dev);
+	if (ret)
+		return ret;
+
+	d->input_dev		= input_dev;
+	d->nb.notifier_call	= yb9_kbdock_nb_call;
+
+	ret = devm_yb9_kbdock_register_notifier(&wdev->dev, &d->nb);
+	if (ret)
+		return ret;
+
+	dev_set_drvdata(&wdev->dev, d);
+	yb9_kbdock_sync(d);
+	return 0;
+}
+
+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",
+		.dev_groups	= yb9_kbdock_groups,
+		.pm		= pm_sleep_ptr(&yb9_kbdock_pm_ops),
+	},
+	.id_table	= yb9_kbdock_block_id_table,
+	.no_singleton	= true,
+	.probe		= yb9_kbdock_block_probe,
+};
+
+/* ------------------------------------------------------------------
+ * Event WMI driver — LENOVO_BTKBD_EVENT
+ * (fires the notifier chain on each WMI event)
+ * ------------------------------------------------------------------ */
+
+static void yb9_kbdock_notify_new(struct wmi_device *wdev,
+				  const struct wmi_buffer *data)
+{
+	/*
+	 * _WED(0xEB) returns EC.BKBD directly as a 32-bit integer
+	 * (LENOVO_BTKBD_EVENT WmiDataId(1) uint32 Status).
+	 */
+	if (!data || data->length < sizeof(__le32))
+		return;
+
+	u32 bkbd = le32_to_cpu(*(const __le32 *)data->data);
+
+	blocking_notifier_call_chain(&yb9_kbdock_chain_head, bkbd, NULL);
+}
+
+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-event",
+	},
+	.id_table	= yb9_kbdock_event_id_table,
+	.no_singleton	= true,
+	.notify_new	= yb9_kbdock_notify_new,
+};
+
+/* ------------------------------------------------------------------
+ * Module init / exit
+ * ------------------------------------------------------------------ */
+
+static const struct dmi_system_id yb9_kbdock_dmi_table[] __initconst = {
+	{
+		/* Lenovo Yoga Book 9 14IAH10 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR,   "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"),
+		},
+	},
+	{ }
+};
+
+static int __init yb9_kbdock_init(void)
+{
+	int ret;
+
+	if (!dmi_check_system(yb9_kbdock_dmi_table))
+		return -ENODEV;
+
+	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");
-- 
2.54.0