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platform/x86/lenovo: Add Yoga Book 9 keyboard dock detection driver

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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>
Link: https://patch.msgid.link/20260728225545.1333610-3-carvsdriver@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
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Dave Carey 2026-07-28 18:55:44 -04:00 • committed by Ilpo Järvinen
commit c9b5c8ff06
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