[PATCH] platform/x86: oxpec: Report tablet mode on OneXPlayer Super X

[Alexander Egorov <begeebe@gmail.com>]

The OneXPlayer Super X has a detachable pogo-pin keyboard which
enumerates as USB device 1a86:1305. The firmware does not expose a
tablet-mode input switch.

Without SW_TABLET_MODE, userspace treats the built-in controller and
other pointer devices as evidence that the system is in laptop mode.
Mutter consequently leaves automatic display rotation disabled after
the keyboard is detached.

On the Super X DMI match, register a persistent input device and report
SW_TABLET_MODE according to the pogo keyboard USB hotplug state. Report
laptop mode while the keyboard is present and tablet mode while it is
absent. Other USB and Bluetooth keyboards do not affect the switch.

Tested on a OneXPlayer Super X with keyboard attach and detach events.
Mutter changes PanelOrientationManaged in both directions and applies
accelerometer-driven display transforms only while the pogo keyboard is
absent.

Development of this patch used assistance from ChatGPT 5.6 sol.

Signed-off-by: Alexander Egorov <begeebe@gmail.com>
---
 drivers/platform/x86/Kconfig |   7 ++-
 drivers/platform/x86/oxpec.c | 110 +++++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index b54b521..3e30127 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -1055,11 +1055,14 @@ config OXP_EC
 	depends on ACPI_EC
 	depends on ACPI_BATTERY
 	depends on HWMON
+	depends on INPUT
+	depends on USB
 	depends on X86
 	help
 		Enables support for the platform EC of OneXPlayer and AOKZOE
-		handheld devices. This includes fan speed, fan controls, and
-		disabling the default TDP behavior of the device.
+		handheld devices. This includes fan speed, fan controls, disabling
+		the default TDP behavior of the device, and tablet mode reporting
+		on supported detachable models.
 
 source "drivers/platform/x86/tuxedo/Kconfig"
 
diff --git a/drivers/platform/x86/oxpec.c b/drivers/platform/x86/oxpec.c
index 99c0dfc..e64ae54 100644
--- a/drivers/platform/x86/oxpec.c
+++ b/drivers/platform/x86/oxpec.c
@@ -18,10 +18,12 @@
 #include <linux/dmi.h>
 #include <linux/hwmon.h>
 #include <linux/init.h>
+#include <linux/input.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/processor.h>
+#include <linux/usb.h>
 #include <acpi/battery.h>
 
 /* Handle ACPI lock mechanism */
@@ -55,6 +57,14 @@ enum oxp_board {
 static enum oxp_board board;
 static struct device *oxp_dev;
 
+struct oxp_platform_data {
+	struct input_dev *tablet_mode_input;
+	struct notifier_block usb_notifier;
+};
+
+#define OXP_SUPER_X_KEYBOARD_VID	0x1a86
+#define OXP_SUPER_X_KEYBOARD_PID	0x1305
+
 /* Fan reading and PWM */
 #define OXP_SENSOR_FAN_REG		0x76 /* Fan reading is 2 registers long */
 #define OXP_2_SENSOR_FAN_REG		0x58 /* Fan reading is 2 registers long */
@@ -292,6 +302,94 @@ static const struct dmi_system_id dmi_table[] = {
 	{},
 };
 
+static bool oxp_is_super_x_keyboard(const struct usb_device *udev)
+{
+	return le16_to_cpu(udev->descriptor.idVendor) == OXP_SUPER_X_KEYBOARD_VID &&
+	       le16_to_cpu(udev->descriptor.idProduct) == OXP_SUPER_X_KEYBOARD_PID;
+}
+
+static void oxp_report_keyboard_attached(struct oxp_platform_data *data,
+					 bool attached)
+{
+	/* SW_TABLET_MODE is set when the detachable keyboard is absent. */
+	input_report_switch(data->tablet_mode_input, SW_TABLET_MODE, !attached);
+	input_sync(data->tablet_mode_input);
+}
+
+static int oxp_find_super_x_keyboard(struct usb_device *udev, void *data)
+{
+	bool *attached = data;
+
+	if (oxp_is_super_x_keyboard(udev))
+		*attached = true;
+
+	return 0;
+}
+
+static int oxp_usb_notify(struct notifier_block *nb,
+			  unsigned long action, void *notify_data)
+{
+	struct oxp_platform_data *data =
+		container_of(nb, struct oxp_platform_data, usb_notifier);
+	struct usb_device *udev = notify_data;
+
+	if (!oxp_is_super_x_keyboard(udev))
+		return NOTIFY_DONE;
+
+	switch (action) {
+	case USB_DEVICE_ADD:
+		oxp_report_keyboard_attached(data, true);
+		break;
+	case USB_DEVICE_REMOVE:
+		oxp_report_keyboard_attached(data, false);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
+static void oxp_unregister_usb_notifier(void *notify_block)
+{
+	usb_unregister_notify(notify_block);
+}
+
+static int oxp_register_super_x_tablet_switch(struct device *dev,
+					      struct oxp_platform_data *data)
+{
+	bool keyboard_attached = false;
+	struct input_dev *input;
+	int ret;
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = "OneXPlayer Super X Tablet Mode Switch";
+	input->phys = "oxp-platform/input0";
+	input->id.bustype = BUS_HOST;
+	input_set_capability(input, EV_SW, SW_TABLET_MODE);
+
+	ret = input_register_device(input);
+	if (ret)
+		return ret;
+
+	data->tablet_mode_input = input;
+	data->usb_notifier.notifier_call = oxp_usb_notify;
+	usb_register_notify(&data->usb_notifier);
+
+	ret = devm_add_action_or_reset(dev, oxp_unregister_usb_notifier,
+				       &data->usb_notifier);
+	if (ret)
+		return ret;
+
+	usb_for_each_dev(&keyboard_attached, oxp_find_super_x_keyboard);
+	oxp_report_keyboard_attached(data, keyboard_attached);
+
+	return 0;
+}
+
 /* Helper functions to handle EC read/write */
 static int read_from_ec(u8 reg, int size, long *val)
 {
@@ -954,6 +1052,18 @@ static int oxp_platform_probe(struct platform_device *pdev)
 			return ret;
 	}
 
+	if (dmi_match(DMI_BOARD_NAME, "ONEXPLAYER SUPER X")) {
+		struct oxp_platform_data *data;
+
+		data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+		if (!data)
+			return -ENOMEM;
+
+		ret = oxp_register_super_x_tablet_switch(dev, data);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 
-- 
2.55.0