Re: [PATCH v13 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver
From: Dave Carey
Date: Wed Jul 22 2026 - 15:03:20 EST
Ugh ... let me check, was trying to do a few different things today at the same time. Appreciate the patience.
-DC
On 7/22/26 10:42 AM, Ilpo Järvinen wrote:
On Wed, 22 Jul 2026, Dave Carey wrote:
The Lenovo Yoga Book 9 14IAH10 ships with a detachable Bluetooth keyboardHi,
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@xxxxxxxxxxxxxxxx>
Reviewed-by: Armin Wolf <W_Armin@xxxxxx>
Signed-off-by: Dave Carey <carvsdriver@xxxxxxxxx>
---
v13:
- Resend of v12: patch was corrupted in transit. git-send-email chose
quoted-printable encoding (triggered by non-ASCII in the changelog)
which encoded '=' as '=3D', corrupting the RST table separators in
the ABI doc and breaking git-am. No content changes from v12.
v12:
- Add #include <linux/sysfs.h> (for sysfs_emit; Ilpo Järvinen)
- Add #include <linux/types.h> (for __le32 and __packed; Ilpo Järvinen)
v11 (addressing Armin Wolf's v10 review):
- ABI doc: correct Date to "June 2027" and KernelVersion to "7.3"
v10 (addressing Armin Wolf's v9 review):
- Update ABI doc: Date: June 2026, KernelVersion: 6.16
- Add #include <linux/compiler_attributes.h> and <linux/types.h>
- yb9_kbdock_query(): change return to pointer-out u32 *bkbd
- struct yb9_kbdock_data: add spinlock_t lock
- yb9_kbdock_report(): hold lock across input_report_switch + input_sync
- yb9_kbdock_sync(): return int, propagate query error to callers
- yb9_kbdock_resume(), yb9_kbdock_block_probe(): propagate sync error
- struct wmi_buffer out: remove zero-initializer
- yb9_kbdock_notify_new(): drop manual length check; use
.min_event_size = sizeof(__le32) in struct wmi_driver instead
.../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..ebe713a
--- /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: June 2027
+KernelVersion: 7.3
+Contact: Dave Carey <carvsdriver@xxxxxxxxx>
+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@xxxxxxxxxxxxxxx
S: Maintained
F: drivers/platform/x86/lenovo/wmi-hotkey-utilities.c
+LENOVO YOGA BOOK 9 KEYBOARD DOCK DRIVER
+M: Dave Carey <carvsdriver@xxxxxxxxx>
+L: platform-driver-x86@xxxxxxxxxxxxxxx
+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@xxxxxxxxxx>
L: linux-input@xxxxxxxxxxxxxxx
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..69c68a0
--- /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.
+ *
+ * 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@xxxxxxxxx>
+ */
+
+#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/sysfs.h>
+#include <linux/types.h>
+#include <linux/wmi.h>
Are you sure you sent the latest version, AFAICT, v12 had this:
+#include <linux/acpi.h>
+#include <linux/cleanup.h>
+#include <linux/compiler_attributes.h>
+#include <linux/dev_printk.h>
...
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/wmi.h>
?