1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * derived from "twidjoy.c"
4 *
5 * Copyright (c) 2008 Martin Kebert
6 * Copyright (c) 2001 Arndt Schoenewald
7 * Copyright (c) 2000-2001 Vojtech Pavlik
8 * Copyright (c) 2000 Mark Fletcher
9 */
10
11 /*
12 * Driver to use 4CH RC transmitter using Zhen Hua 5-byte protocol (Walkera Lama,
13 * EasyCopter etc.) as a joystick under Linux.
14 *
15 * RC transmitters using Zhen Hua 5-byte protocol are cheap four channels
16 * transmitters for control a RC planes or RC helicopters with possibility to
17 * connect on a serial port.
18 * Data coming from transmitter is in this order:
19 * 1. byte = synchronisation byte
20 * 2. byte = X axis
21 * 3. byte = Y axis
22 * 4. byte = RZ axis
23 * 5. byte = Z axis
24 * (and this is repeated)
25 *
26 * For questions or feedback regarding this driver module please contact:
27 * Martin Kebert <gkmarty@gmail.com> - but I am not a C-programmer nor kernel
28 * coder :-(
29 */
30
31 /*
32 */
33
34 #include <linux/kernel.h>
35 #include <linux/module.h>
36 #include <linux/slab.h>
37 #include <linux/bitrev.h>
38 #include <linux/input.h>
39 #include <linux/serio.h>
40
41 #define DRIVER_DESC "RC transmitter with 5-byte Zhen Hua protocol joystick driver"
42
43 MODULE_DESCRIPTION(DRIVER_DESC);
44 MODULE_LICENSE("GPL");
45
46 /*
47 * Constants.
48 */
49
50 #define ZHENHUA_MAX_LENGTH 5
51
52 /*
53 * Zhen Hua data.
54 */
55
56 struct zhenhua {
57 struct input_dev *dev;
58 int idx;
59 unsigned char data[ZHENHUA_MAX_LENGTH];
60 char phys[32];
61 };
62
63 /*
64 * zhenhua_process_packet() decodes packets the driver receives from the
65 * RC transmitter. It updates the data accordingly.
66 */
67
zhenhua_process_packet(struct zhenhua * zhenhua)68 static void zhenhua_process_packet(struct zhenhua *zhenhua)
69 {
70 struct input_dev *dev = zhenhua->dev;
71 unsigned char *data = zhenhua->data;
72
73 input_report_abs(dev, ABS_Y, data[1]);
74 input_report_abs(dev, ABS_X, data[2]);
75 input_report_abs(dev, ABS_RZ, data[3]);
76 input_report_abs(dev, ABS_Z, data[4]);
77
78 input_sync(dev);
79 }
80
81 /*
82 * zhenhua_interrupt() is called by the low level driver when characters
83 * are ready for us. We then buffer them for further processing, or call the
84 * packet processing routine.
85 */
86
zhenhua_interrupt(struct serio * serio,unsigned char data,unsigned int flags)87 static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags)
88 {
89 struct zhenhua *zhenhua = serio_get_drvdata(serio);
90
91 /* All Zhen Hua packets are 5 bytes. The fact that the first byte
92 * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200)
93 * can be used to check and regain sync. */
94
95 if (data == 0xef)
96 zhenhua->idx = 0; /* this byte starts a new packet */
97 else if (zhenhua->idx == 0)
98 return IRQ_HANDLED; /* wrong MSB -- ignore this byte */
99
100 if (zhenhua->idx < ZHENHUA_MAX_LENGTH)
101 zhenhua->data[zhenhua->idx++] = bitrev8(data);
102
103 if (zhenhua->idx == ZHENHUA_MAX_LENGTH) {
104 zhenhua_process_packet(zhenhua);
105 zhenhua->idx = 0;
106 }
107
108 return IRQ_HANDLED;
109 }
110
111 /*
112 * zhenhua_disconnect() is the opposite of zhenhua_connect()
113 */
114
zhenhua_disconnect(struct serio * serio)115 static void zhenhua_disconnect(struct serio *serio)
116 {
117 struct zhenhua *zhenhua = serio_get_drvdata(serio);
118
119 serio_close(serio);
120 serio_set_drvdata(serio, NULL);
121 input_unregister_device(zhenhua->dev);
122 kfree(zhenhua);
123 }
124
125 /*
126 * zhenhua_connect() is the routine that is called when someone adds a
127 * new serio device. It looks for the Twiddler, and if found, registers
128 * it as an input device.
129 */
130
zhenhua_connect(struct serio * serio,struct serio_driver * drv)131 static int zhenhua_connect(struct serio *serio, struct serio_driver *drv)
132 {
133 struct zhenhua *zhenhua;
134 struct input_dev *input_dev;
135 int err = -ENOMEM;
136
137 zhenhua = kzalloc(sizeof(struct zhenhua), GFP_KERNEL);
138 input_dev = input_allocate_device();
139 if (!zhenhua || !input_dev)
140 goto fail1;
141
142 zhenhua->dev = input_dev;
143 snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys);
144
145 input_dev->name = "Zhen Hua 5-byte device";
146 input_dev->phys = zhenhua->phys;
147 input_dev->id.bustype = BUS_RS232;
148 input_dev->id.vendor = SERIO_ZHENHUA;
149 input_dev->id.product = 0x0001;
150 input_dev->id.version = 0x0100;
151 input_dev->dev.parent = &serio->dev;
152
153 input_dev->evbit[0] = BIT(EV_ABS);
154 input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0);
155 input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0);
156 input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0);
157 input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0);
158
159 serio_set_drvdata(serio, zhenhua);
160
161 err = serio_open(serio, drv);
162 if (err)
163 goto fail2;
164
165 err = input_register_device(zhenhua->dev);
166 if (err)
167 goto fail3;
168
169 return 0;
170
171 fail3: serio_close(serio);
172 fail2: serio_set_drvdata(serio, NULL);
173 fail1: input_free_device(input_dev);
174 kfree(zhenhua);
175 return err;
176 }
177
178 /*
179 * The serio driver structure.
180 */
181
182 static const struct serio_device_id zhenhua_serio_ids[] = {
183 {
184 .type = SERIO_RS232,
185 .proto = SERIO_ZHENHUA,
186 .id = SERIO_ANY,
187 .extra = SERIO_ANY,
188 },
189 { 0 }
190 };
191
192 MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
193
194 static struct serio_driver zhenhua_drv = {
195 .driver = {
196 .name = "zhenhua",
197 },
198 .description = DRIVER_DESC,
199 .id_table = zhenhua_serio_ids,
200 .interrupt = zhenhua_interrupt,
201 .connect = zhenhua_connect,
202 .disconnect = zhenhua_disconnect,
203 };
204
205 module_serio_driver(zhenhua_drv);
206
