1/* SPDX-License-Identifier: GPL-2.0 */
 2/*
 3 * Helper code to detect 360 degree hinges (yoga) style 2-in-1 devices using 2 accelerometers
 4 * to allow the OS to determine the angle between the display and the base of the device.
 5 *
 6 * On Windows these are read by a special HingeAngleService process which calls undocumented
 7 * ACPI methods, to let the firmware know if the 2-in-1 is in tablet- or laptop-mode.
 8 * The firmware may use this to disable the kbd and touchpad to avoid spurious input in
 9 * tablet-mode as well as to report SW_TABLET_MODE info to the OS.
10 *
11 * Since Linux does not call these undocumented methods, the SW_TABLET_MODE info reported
12 * by various drivers/platform/x86 drivers is incorrect. These drivers use the detection
13 * code in this file to disable SW_TABLET_MODE reporting to avoid reporting broken info
14 * (instead userspace can derive the status itself by directly reading the 2 accels).
15 */
16
17#include <linux/acpi.h>
18#include <linux/i2c.h>
19
20static int dual_accel_i2c_resource_count(struct acpi_resource *ares, void *data)
21{
22	struct acpi_resource_i2c_serialbus *sb;
23	int *count = data;
24
25	if (i2c_acpi_get_i2c_resource(ares, &sb))
26		*count = *count + 1;
27
28	return 1;
29}
30
31static int dual_accel_i2c_client_count(struct acpi_device *adev)
32{
33	int ret, count = 0;
34	LIST_HEAD(r);
35
36	ret = acpi_dev_get_resources(adev, &r, dual_accel_i2c_resource_count, &count);
37	if (ret < 0)
38		return ret;
39
40	acpi_dev_free_resource_list(&r);
41	return count;
42}
43
44static bool dual_accel_detect_bosc0200(void)
45{
46	struct acpi_device *adev;
47	int count;
48
49	adev = acpi_dev_get_first_match_dev("BOSC0200", NULL, -1);
50	if (!adev)
51		return false;
52
53	count = dual_accel_i2c_client_count(adev);
54
55	acpi_dev_put(adev);
56
57	return count == 2;
58}
59
60static bool dual_accel_detect(void)
61{
62	/* Systems which use a pair of accels with KIOX010A / KIOX020A ACPI ids */
63	if (acpi_dev_present("KIOX010A", NULL, -1) &&
64	    acpi_dev_present("KIOX020A", NULL, -1))
65		return true;
66
67	/* Systems which use a single DUAL250E ACPI device to model 2 accels */
68	if (acpi_dev_present("DUAL250E", NULL, -1))
69		return true;
70
71	/* Systems which use a single BOSC0200 ACPI device to model 2 accels */
72	if (dual_accel_detect_bosc0200())
73		return true;
74
75	return false;
76}