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