Re: [PATCH v13 2/2] platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Wed, 22 Jul 2026, Dave Carey wrote:

> The Lenovo Yoga Book 9 14IAH10 ships with a detachable Bluetooth keyboard
> that magnetically attaches to the bottom (secondary) screen in one of two
> positions.  The Embedded Controller tracks the attachment state in a 2-bit
> field called BKBD 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>
> Reviewed-by: Armin Wolf <W_Armin@gmx.de>
> Signed-off-by: Dave Carey <carvsdriver@gmail.com>
> ---
> 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@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..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@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/sysfs.h>
> +#include <linux/types.h>
> +#include <linux/wmi.h>

Hi,

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>

?

-- 
 i.