Re: [PATCH v11 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 Tue, 23 Jun 2026, Dave Carey wrote:

> The Lenovo Yoga Book 9 14IAH10 ships with a detachable Bluetooth keyboard
> that magnetically attaches to the bottom (secondary) screen in one of two
> positions.  The Embedded Controller tracks the attachment state in a 2-bit
> field called BKBD 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>
> ---
> v11:
> - ABI doc: correct Date to "June 2027" and KernelVersion to "7.3"; these
>   fields should reflect when the ABI lands in the kernel, not the
>   submission date (Armin Wolf).
> 
> 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      | 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..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..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;

Add includes for __packed and __le32.

> +
> +/* ------------------------------------------------------------------
> + * 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);

Add include.

> +}
> +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");
> 

-- 
 i.