1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/platform/x86/dual_accel_detect.h b/drivers/platform/x86/dual_accel_detect.h
new file mode 100644
index 000000000000..a9eae17cc43d
--- /dev/null
+++ b/drivers/platform/x86/dual_accel_detect.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Helper code to detect 360 degree hinges (yoga) style 2-in-1 devices using 2 accelerometers
+ * to allow the OS to determine the angle between the display and the base of the device.
+ *
+ * On Windows these are read by a special HingeAngleService process which calls undocumented
+ * ACPI methods, to let the firmware know if the 2-in-1 is in tablet- or laptop-mode.
+ * The firmware may use this to disable the kbd and touchpad to avoid spurious input in
+ * tablet-mode as well as to report SW_TABLET_MODE info to the OS.
+ *
+ * Since Linux does not call these undocumented methods, the SW_TABLET_MODE info reported
+ * by various drivers/platform/x86 drivers is incorrect. These drivers use the detection
+ * code in this file to disable SW_TABLET_MODE reporting to avoid reporting broken info
+ * (instead userspace can derive the status itself by directly reading the 2 accels).
+ */
+
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+
+static int dual_accel_i2c_resource_count(struct acpi_resource *ares, void *data)
+{
+	struct acpi_resource_i2c_serialbus *sb;
+	int *count = data;
+
+	if (i2c_acpi_get_i2c_resource(ares, &sb))
+		*count = *count + 1;
+
+	return 1;
+}
+
+static int dual_accel_i2c_client_count(struct acpi_device *adev)
+{
+	int ret, count = 0;
+	LIST_HEAD(r);
+
+	ret = acpi_dev_get_resources(adev, &r, dual_accel_i2c_resource_count, &count);
+	if (ret < 0)
+		return ret;
+
+	acpi_dev_free_resource_list(&r);
+	return count;
+}
+
+static bool dual_accel_detect_bosc0200(void)
+{
+	struct acpi_device *adev;
+	int count;
+
+	adev = acpi_dev_get_first_match_dev("BOSC0200", NULL, -1);
+	if (!adev)
+		return false;
+
+	count = dual_accel_i2c_client_count(adev);
+
+	acpi_dev_put(adev);
+
+	return count == 2;
+}
+
+static bool dual_accel_detect(void)
+{
+	/* Systems which use a pair of accels with KIOX010A / KIOX020A ACPI ids */
+	if (acpi_dev_present("KIOX010A", NULL, -1) &&
+	    acpi_dev_present("KIOX020A", NULL, -1))
+		return true;
+
+	/* Systems which use a single DUAL250E ACPI device to model 2 accels */
+	if (acpi_dev_present("DUAL250E", NULL, -1))
+		return true;
+
+	/* Systems which use a single BOSC0200 ACPI device to model 2 accels */
+	if (dual_accel_detect_bosc0200())
+		return true;
+
+	return false;
+}