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 20 static 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 31 static 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 44 static 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 60 static 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 } 77