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
44 struct lg3ff_device {
45 struct hid_report *report;
46 };
47
hid_lg3ff_play(struct input_dev * dev,void * data,struct ff_effect * effect)48 static int hid_lg3ff_play(struct input_dev *dev, void *data,
49 struct ff_effect *effect)
50 {
51 struct hid_device *hid = input_get_drvdata(dev);
52 struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
53 struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
54 int x, y;
55
56 /*
57 * Available values in the field should always be 63, but we only use up to
58 * 35. Instead, clear the entire area, however big it is.
59 */
60 memset(report->field[0]->value, 0,
61 sizeof(__s32) * report->field[0]->report_count);
62
63 switch (effect->type) {
64 case FF_CONSTANT:
65 /*
66 * Already clamped in ff_memless
67 * 0 is center (different then other logitech)
68 */
69 x = effect->u.ramp.start_level;
70 y = effect->u.ramp.end_level;
71
72 /* send command byte */
73 report->field[0]->value[0] = 0x51;
74
75 /*
76 * Sign backwards from other Force3d pro
77 * which get recast here in two's complement 8 bits
78 */
79 report->field[0]->value[1] = (unsigned char)(-x);
80 report->field[0]->value[31] = (unsigned char)(-y);
81
82 hid_hw_request(hid, report, HID_REQ_SET_REPORT);
83 break;
84 }
85 return 0;
86 }
hid_lg3ff_set_autocenter(struct input_dev * dev,u16 magnitude)87 static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
88 {
89 struct hid_device *hid = input_get_drvdata(dev);
90 struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
91 struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
92
93 /*
94 * Auto Centering probed from device
95 * NOTE: deadman's switch on G940 must be covered
96 * for effects to work
97 */
98 report->field[0]->value[0] = 0x51;
99 report->field[0]->value[1] = 0x00;
100 report->field[0]->value[2] = 0x00;
101 report->field[0]->value[3] = 0x7F;
102 report->field[0]->value[4] = 0x7F;
103 report->field[0]->value[31] = 0x00;
104 report->field[0]->value[32] = 0x00;
105 report->field[0]->value[33] = 0x7F;
106 report->field[0]->value[34] = 0x7F;
107
108 hid_hw_request(hid, report, HID_REQ_SET_REPORT);
109 }
110
111
112 static const signed short ff3_joystick_ac[] = {
113 FF_CONSTANT,
114 FF_AUTOCENTER,
115 -1
116 };
117
lg3ff_init(struct hid_device * hid)118 int lg3ff_init(struct hid_device *hid)
119 {
120 struct hid_input *hidinput;
121 struct input_dev *dev;
122 const signed short *ff_bits = ff3_joystick_ac;
123 int error;
124 int i;
125
126 if (list_empty(&hid->inputs)) {
127 hid_err(hid, "no inputs found\n");
128 return -ENODEV;
129 }
130 hidinput = list_entry(hid->inputs.next, struct hid_input, list);
131 dev = hidinput->input;
132
133 /* Check that the report looks ok */
134 if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 35))
135 return -ENODEV;
136
137 /* Assume single fixed device G940 */
138 for (i = 0; ff_bits[i] >= 0; i++)
139 set_bit(ff_bits[i], dev->ffbit);
140
141 error = input_ff_create_memless(dev, NULL, hid_lg3ff_play);
142 if (error)
143 return error;
144
145 if (test_bit(FF_AUTOCENTER, dev->ffbit))
146 dev->ff->set_autocenter = hid_lg3ff_set_autocenter;
147
148 hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@gmail.com>\n");
149 return 0;
150 }
151
152