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