xref: /linux/drivers/platform/x86/lenovo/yb9-kbdock.c (revision 5b05bb3f6c5716fab6911e12d60dd1f43ad9806a)

// 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/compiler_attributes.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/spinlock.h>
#include <linux/sysfs.h>
#include <linux/types.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;
	spinlock_t		 lock;	/* protects input_report_switch + input_sync */
};

static int yb9_kbdock_query(struct yb9_kbdock_data *d, u32 *bkbd)
{
	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;

	*bkbd = le32_to_cpu(fs->status);
	return 0;
}

static void yb9_kbdock_report(struct yb9_kbdock_data *d, u32 bkbd)
{
	int tablet = (bkbd == BKBD_DETACHED) ? 1 : 0;

	spin_lock(&d->lock);
	input_report_switch(d->input_dev, SW_TABLET_MODE, tablet);
	input_sync(d->input_dev);
	spin_unlock(&d->lock);
	dev_dbg(&d->wdev->dev, "BKBD=%u SW_TABLET_MODE=%d\n", bkbd, tablet);
}

static int yb9_kbdock_sync(struct yb9_kbdock_data *d)
{
	u32 bkbd;
	int ret;

	ret = yb9_kbdock_query(d, &bkbd);
	if (ret)
		return ret;

	yb9_kbdock_report(d, bkbd);
	return 0;
}

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);
	u32 bkbd;
	int ret;

	ret = yb9_kbdock_query(d, &bkbd);
	if (ret)
		return ret;
	return sysfs_emit(buf, "%u\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);

	return yb9_kbdock_sync(d);
}
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;
	spin_lock_init(&d->lock);

	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);
	return yb9_kbdock_sync(d);
}

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).
	 * Short-buffer guard is handled by .min_event_size below.
	 */
	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,
	.min_event_size	= sizeof(__le32),
};

/* ------------------------------------------------------------------
 * 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");