platform/x86: Add and use a dual_accel_detect() helper

Various 360 degree hinges (yoga) style 2-in-1 devices use 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 pdx86 drivers is incorrect on these devices.

Before this commit the intel-hid and thinkpad_acpi code already had 2
hardcoded checks for ACPI hardware-ids of dual-accel sensors to avoid
reporting broken info.

And now we also have a bug-report about the same problem in the intel-vbtn
code. Since there are at least 3 different ACPI hardware-ids in play, add
a new dual_accel_detect() helper which checks for all 3, rather then
adding different hardware-ids to the drivers as bug-reports trickle in.
Having shared code which checks all known hardware-ids is esp. important
for the intel-hid and intel-vbtn drivers as these are generic drivers
which are used on a lot of devices.

The BOSC0200 hardware-id requires special handling, because often it is
used for a single-accelerometer setup. Only in a few cases it refers to
a dual-accel setup, in which case there will be 2 I2cSerialBus resources
in the device's resource-list, so the helper checks for this.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=209011
Reported-and-tested-by: Julius Lehmann <julius@devpi.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210729082134.6683-1-hdegoede@redhat.com

1 files changed, 75 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..1a069159da91
--- /dev/null
+++ b/drivers/platform/x86/dual_accel_detect.h
@@ -0,0 +1,75 @@
+/* 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))
+		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;
+}