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/drivers/media/rc/ir-nec-decoder.c

https://bitbucket.org/wisechild/galaxy-nexus
C | 226 lines | 162 code | 40 blank | 24 comment | 39 complexity | 9cb2e111b536e753e0d7ec9a88efaf5f MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  1/* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
  2 *
  3 * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
  4 *
  5 * This program is free software; you can redistribute it and/or modify
  6 *  it under the terms of the GNU General Public License as published by
  7 *  the Free Software Foundation version 2 of the License.
  8 *
  9 *  This program is distributed in the hope that it will be useful,
 10 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 *  GNU General Public License for more details.
 13 */
 14
 15#include <linux/bitrev.h>
 16#include "rc-core-priv.h"
 17
 18#define NEC_NBITS		32
 19#define NEC_UNIT		562500  /* ns */
 20#define NEC_HEADER_PULSE	(16 * NEC_UNIT)
 21#define NECX_HEADER_PULSE	(8  * NEC_UNIT) /* Less common NEC variant */
 22#define NEC_HEADER_SPACE	(8  * NEC_UNIT)
 23#define NEC_REPEAT_SPACE	(4  * NEC_UNIT)
 24#define NEC_BIT_PULSE		(1  * NEC_UNIT)
 25#define NEC_BIT_0_SPACE		(1  * NEC_UNIT)
 26#define NEC_BIT_1_SPACE		(3  * NEC_UNIT)
 27#define	NEC_TRAILER_PULSE	(1  * NEC_UNIT)
 28#define	NEC_TRAILER_SPACE	(10 * NEC_UNIT) /* even longer in reality */
 29#define NECX_REPEAT_BITS	1
 30
 31enum nec_state {
 32	STATE_INACTIVE,
 33	STATE_HEADER_SPACE,
 34	STATE_BIT_PULSE,
 35	STATE_BIT_SPACE,
 36	STATE_TRAILER_PULSE,
 37	STATE_TRAILER_SPACE,
 38};
 39
 40/**
 41 * ir_nec_decode() - Decode one NEC pulse or space
 42 * @dev:	the struct rc_dev descriptor of the device
 43 * @duration:	the struct ir_raw_event descriptor of the pulse/space
 44 *
 45 * This function returns -EINVAL if the pulse violates the state machine
 46 */
 47static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
 48{
 49	struct nec_dec *data = &dev->raw->nec;
 50	u32 scancode;
 51	u8 address, not_address, command, not_command;
 52	bool send_32bits = false;
 53
 54	if (!(dev->raw->enabled_protocols & RC_TYPE_NEC))
 55		return 0;
 56
 57	if (!is_timing_event(ev)) {
 58		if (ev.reset)
 59			data->state = STATE_INACTIVE;
 60		return 0;
 61	}
 62
 63	IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
 64		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 65
 66	switch (data->state) {
 67
 68	case STATE_INACTIVE:
 69		if (!ev.pulse)
 70			break;
 71
 72		if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT / 2)) {
 73			data->is_nec_x = false;
 74			data->necx_repeat = false;
 75		} else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
 76			data->is_nec_x = true;
 77		else
 78			break;
 79
 80		data->count = 0;
 81		data->state = STATE_HEADER_SPACE;
 82		return 0;
 83
 84	case STATE_HEADER_SPACE:
 85		if (ev.pulse)
 86			break;
 87
 88		if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
 89			data->state = STATE_BIT_PULSE;
 90			return 0;
 91		} else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
 92			if (!dev->keypressed) {
 93				IR_dprintk(1, "Discarding last key repeat: event after key up\n");
 94			} else {
 95				rc_repeat(dev);
 96				IR_dprintk(1, "Repeat last key\n");
 97				data->state = STATE_TRAILER_PULSE;
 98			}
 99			return 0;
100		}
101
102		break;
103
104	case STATE_BIT_PULSE:
105		if (!ev.pulse)
106			break;
107
108		if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
109			break;
110
111		data->state = STATE_BIT_SPACE;
112		return 0;
113
114	case STATE_BIT_SPACE:
115		if (ev.pulse)
116			break;
117
118		if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
119			geq_margin(ev.duration,
120			NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
121				IR_dprintk(1, "Repeat last key\n");
122				rc_repeat(dev);
123				data->state = STATE_INACTIVE;
124				return 0;
125
126		} else if (data->count > NECX_REPEAT_BITS)
127			data->necx_repeat = false;
128
129		data->bits <<= 1;
130		if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
131			data->bits |= 1;
132		else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
133			break;
134		data->count++;
135
136		if (data->count == NEC_NBITS)
137			data->state = STATE_TRAILER_PULSE;
138		else
139			data->state = STATE_BIT_PULSE;
140
141		return 0;
142
143	case STATE_TRAILER_PULSE:
144		if (!ev.pulse)
145			break;
146
147		if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
148			break;
149
150		data->state = STATE_TRAILER_SPACE;
151		return 0;
152
153	case STATE_TRAILER_SPACE:
154		if (ev.pulse)
155			break;
156
157		if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
158			break;
159
160		address     = bitrev8((data->bits >> 24) & 0xff);
161		not_address = bitrev8((data->bits >> 16) & 0xff);
162		command	    = bitrev8((data->bits >>  8) & 0xff);
163		not_command = bitrev8((data->bits >>  0) & 0xff);
164
165		if ((command ^ not_command) != 0xff) {
166			IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
167				   data->bits);
168			send_32bits = true;
169		}
170
171		if (send_32bits) {
172			/* NEC transport, but modified protocol, used by at
173			 * least Apple and TiVo remotes */
174			scancode = data->bits;
175			IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
176		} else if ((address ^ not_address) != 0xff) {
177			/* Extended NEC */
178			scancode = address     << 16 |
179				   not_address <<  8 |
180				   command;
181			IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
182		} else {
183			/* Normal NEC */
184			scancode = address << 8 | command;
185			IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
186		}
187
188		if (data->is_nec_x)
189			data->necx_repeat = true;
190
191		rc_keydown(dev, scancode, 0);
192		data->state = STATE_INACTIVE;
193		return 0;
194	}
195
196	IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
197		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
198	data->state = STATE_INACTIVE;
199	return -EINVAL;
200}
201
202static struct ir_raw_handler nec_handler = {
203	.protocols	= RC_TYPE_NEC,
204	.decode		= ir_nec_decode,
205};
206
207static int __init ir_nec_decode_init(void)
208{
209	ir_raw_handler_register(&nec_handler);
210
211	printk(KERN_INFO "IR NEC protocol handler initialized\n");
212	return 0;
213}
214
215static void __exit ir_nec_decode_exit(void)
216{
217	ir_raw_handler_unregister(&nec_handler);
218}
219
220module_init(ir_nec_decode_init);
221module_exit(ir_nec_decode_exit);
222
223MODULE_LICENSE("GPL");
224MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
225MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
226MODULE_DESCRIPTION("NEC IR protocol decoder");