1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Force feedback support for Logitech Flight System G940
4 *
5 * Copyright (c) 2009 Gary Stein <LordCnidarian@gmail.com>
6 */
7
8/*
9 */
10
11
12#include <linux/input.h>
13#include <linux/hid.h>
14
15#include "hid-lg.h"
16
17/*
18 * G940 Theory of Operation (from experimentation)
19 *
20 * There are 63 fields (only 3 of them currently used)
21 * 0 - seems to be command field
22 * 1 - 30 deal with the x axis
23 * 31 -60 deal with the y axis
24 *
25 * Field 1 is x axis constant force
26 * Field 31 is y axis constant force
27 *
28 * other interesting fields 1,2,3,4 on x axis
29 * (same for 31,32,33,34 on y axis)
30 *
31 * 0 0 127 127 makes the joystick autocenter hard
32 *
33 * 127 0 127 127 makes the joystick loose on the right,
34 * but stops all movemnt left
35 *
36 * -127 0 -127 -127 makes the joystick loose on the left,
37 * but stops all movement right
38 *
39 * 0 0 -127 -127 makes the joystick rattle very hard
40 *
41 * I'm sure these are effects that I don't know enough about them
42 */
43
44static int hid_lg3ff_play(struct input_dev *dev, void *data,
45 struct ff_effect *effect)
46{
47 struct hid_device *hid = input_get_drvdata(dev);
48 struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
49 struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
50 int x, y;
51
52/*
53 * Available values in the field should always be 63, but we only use up to
54 * 35. Instead, clear the entire area, however big it is.
55 */
56 memset(report->field[0]->value, 0,
57 sizeof(__s32) * report->field[0]->report_count);
58
59 switch (effect->type) {
60 case FF_CONSTANT:
61/*
62 * Already clamped in ff_memless
63 * 0 is center (different then other logitech)
64 */
65 x = effect->u.ramp.start_level;
66 y = effect->u.ramp.end_level;
67
68 /* send command byte */
69 report->field[0]->value[0] = 0x51;
70
71/*
72 * Sign backwards from other Force3d pro
73 * which get recast here in two's complement 8 bits
74 */
75 report->field[0]->value[1] = (unsigned char)(-x);
76 report->field[0]->value[31] = (unsigned char)(-y);
77
78 hid_hw_request(hdev: hid, report, reqtype: HID_REQ_SET_REPORT);
79 break;
80 }
81 return 0;
82}
83static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
84{
85 struct hid_device *hid = input_get_drvdata(dev);
86 struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
87 struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
88
89/*
90 * Auto Centering probed from device
91 * NOTE: deadman's switch on G940 must be covered
92 * for effects to work
93 */
94 report->field[0]->value[0] = 0x51;
95 report->field[0]->value[1] = 0x00;
96 report->field[0]->value[2] = 0x00;
97 report->field[0]->value[3] = 0x7F;
98 report->field[0]->value[4] = 0x7F;
99 report->field[0]->value[31] = 0x00;
100 report->field[0]->value[32] = 0x00;
101 report->field[0]->value[33] = 0x7F;
102 report->field[0]->value[34] = 0x7F;
103
104 hid_hw_request(hdev: hid, report, reqtype: HID_REQ_SET_REPORT);
105}
106
107
108static const signed short ff3_joystick_ac[] = {
109 FF_CONSTANT,
110 FF_AUTOCENTER,
111 -1
112};
113
114int lg3ff_init(struct hid_device *hid)
115{
116 struct hid_input *hidinput;
117 struct input_dev *dev;
118 const signed short *ff_bits = ff3_joystick_ac;
119 int error;
120 int i;
121
122 if (list_empty(head: &hid->inputs)) {
123 hid_err(hid, "no inputs found\n");
124 return -ENODEV;
125 }
126 hidinput = list_entry(hid->inputs.next, struct hid_input, list);
127 dev = hidinput->input;
128
129 /* Check that the report looks ok */
130 if (!hid_validate_values(hid, type: HID_OUTPUT_REPORT, id: 0, field_index: 0, report_counts: 35))
131 return -ENODEV;
132
133 /* Assume single fixed device G940 */
134 for (i = 0; ff_bits[i] >= 0; i++)
135 set_bit(nr: ff_bits[i], addr: dev->ffbit);
136
137 error = input_ff_create_memless(dev, NULL, play_effect: hid_lg3ff_play);
138 if (error)
139 return error;
140
141 if (test_bit(FF_AUTOCENTER, dev->ffbit))
142 dev->ff->set_autocenter = hid_lg3ff_set_autocenter;
143
144 hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@gmail.com>\n");
145 return 0;
146}
147
148

source code of linux/drivers/hid/hid-lg3ff.c