1/*
2 *  derived from "twidjoy.c"
3 *
4 *  Copyright (c) 2008 Martin Kebert
5 *  Copyright (c) 2001 Arndt Schoenewald
6 *  Copyright (c) 2000-2001 Vojtech Pavlik
7 *  Copyright (c) 2000 Mark Fletcher
8 *
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 * This program is free software; you can redistribute it and/or modify
33 * it under the terms of the GNU General Public License as published by
34 * the Free Software Foundation; either version 2 of the License, or
35 * (at your option) any later version.
36 *
37 * This program is distributed in the hope that it will be useful,
38 * but WITHOUT ANY WARRANTY; without even the implied warranty of
39 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
40 * GNU General Public License for more details.
41 *
42 * You should have received a copy of the GNU General Public License
43 * along with this program; if not, write to the Free Software
44 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
45 */
46
47#include <linux/kernel.h>
48#include <linux/module.h>
49#include <linux/slab.h>
50#include <linux/input.h>
51#include <linux/serio.h>
52
53#define DRIVER_DESC	"RC transmitter with 5-byte Zhen Hua protocol joystick driver"
54
55MODULE_DESCRIPTION(DRIVER_DESC);
56MODULE_LICENSE("GPL");
57
58/*
59 * Constants.
60 */
61
62#define ZHENHUA_MAX_LENGTH 5
63
64/*
65 * Zhen Hua data.
66 */
67
68struct zhenhua {
69	struct input_dev *dev;
70	int idx;
71	unsigned char data[ZHENHUA_MAX_LENGTH];
72	char phys[32];
73};
74
75
76/* bits in all incoming bytes needs to be "reversed" */
77static int zhenhua_bitreverse(int x)
78{
79	x = ((x & 0xaa) >> 1) | ((x & 0x55) << 1);
80	x = ((x & 0xcc) >> 2) | ((x & 0x33) << 2);
81	x = ((x & 0xf0) >> 4) | ((x & 0x0f) << 4);
82	return x;
83}
84
85/*
86 * zhenhua_process_packet() decodes packets the driver receives from the
87 * RC transmitter. It updates the data accordingly.
88 */
89
90static void zhenhua_process_packet(struct zhenhua *zhenhua)
91{
92	struct input_dev *dev = zhenhua->dev;
93	unsigned char *data = zhenhua->data;
94
95	input_report_abs(dev, ABS_Y, data[1]);
96	input_report_abs(dev, ABS_X, data[2]);
97	input_report_abs(dev, ABS_RZ, data[3]);
98	input_report_abs(dev, ABS_Z, data[4]);
99
100	input_sync(dev);
101}
102
103/*
104 * zhenhua_interrupt() is called by the low level driver when characters
105 * are ready for us. We then buffer them for further processing, or call the
106 * packet processing routine.
107 */
108
109static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags)
110{
111	struct zhenhua *zhenhua = serio_get_drvdata(serio);
112
113	/* All Zhen Hua packets are 5 bytes. The fact that the first byte
114	 * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200)
115	 * can be used to check and regain sync. */
116
117	if (data == 0xef)
118		zhenhua->idx = 0;	/* this byte starts a new packet */
119	else if (zhenhua->idx == 0)
120		return IRQ_HANDLED;	/* wrong MSB -- ignore this byte */
121
122	if (zhenhua->idx < ZHENHUA_MAX_LENGTH)
123		zhenhua->data[zhenhua->idx++] = zhenhua_bitreverse(data);
124
125	if (zhenhua->idx == ZHENHUA_MAX_LENGTH) {
126		zhenhua_process_packet(zhenhua);
127		zhenhua->idx = 0;
128	}
129
130	return IRQ_HANDLED;
131}
132
133/*
134 * zhenhua_disconnect() is the opposite of zhenhua_connect()
135 */
136
137static void zhenhua_disconnect(struct serio *serio)
138{
139	struct zhenhua *zhenhua = serio_get_drvdata(serio);
140
141	serio_close(serio);
142	serio_set_drvdata(serio, NULL);
143	input_unregister_device(zhenhua->dev);
144	kfree(zhenhua);
145}
146
147/*
148 * zhenhua_connect() is the routine that is called when someone adds a
149 * new serio device. It looks for the Twiddler, and if found, registers
150 * it as an input device.
151 */
152
153static int zhenhua_connect(struct serio *serio, struct serio_driver *drv)
154{
155	struct zhenhua *zhenhua;
156	struct input_dev *input_dev;
157	int err = -ENOMEM;
158
159	zhenhua = kzalloc(sizeof(struct zhenhua), GFP_KERNEL);
160	input_dev = input_allocate_device();
161	if (!zhenhua || !input_dev)
162		goto fail1;
163
164	zhenhua->dev = input_dev;
165	snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys);
166
167	input_dev->name = "Zhen Hua 5-byte device";
168	input_dev->phys = zhenhua->phys;
169	input_dev->id.bustype = BUS_RS232;
170	input_dev->id.vendor = SERIO_ZHENHUA;
171	input_dev->id.product = 0x0001;
172	input_dev->id.version = 0x0100;
173	input_dev->dev.parent = &serio->dev;
174
175	input_dev->evbit[0] = BIT(EV_ABS);
176	input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0);
177	input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0);
178	input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0);
179	input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0);
180
181	serio_set_drvdata(serio, zhenhua);
182
183	err = serio_open(serio, drv);
184	if (err)
185		goto fail2;
186
187	err = input_register_device(zhenhua->dev);
188	if (err)
189		goto fail3;
190
191	return 0;
192
193 fail3:	serio_close(serio);
194 fail2:	serio_set_drvdata(serio, NULL);
195 fail1:	input_free_device(input_dev);
196	kfree(zhenhua);
197	return err;
198}
199
200/*
201 * The serio driver structure.
202 */
203
204static struct serio_device_id zhenhua_serio_ids[] = {
205	{
206		.type	= SERIO_RS232,
207		.proto	= SERIO_ZHENHUA,
208		.id	= SERIO_ANY,
209		.extra	= SERIO_ANY,
210	},
211	{ 0 }
212};
213
214MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
215
216static struct serio_driver zhenhua_drv = {
217	.driver		= {
218		.name	= "zhenhua",
219	},
220	.description	= DRIVER_DESC,
221	.id_table	= zhenhua_serio_ids,
222	.interrupt	= zhenhua_interrupt,
223	.connect	= zhenhua_connect,
224	.disconnect	= zhenhua_disconnect,
225};
226
227module_serio_driver(zhenhua_drv);
228