1 /* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol 2 * 3 * Copyright (C) 2010 by Mauro Carvalho Chehab 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 <linux/module.h> 17 #include "rc-core-priv.h" 18 19 #define NEC_NBITS 32 20 #define NEC_UNIT 562500 /* ns */ 21 #define NEC_HEADER_PULSE (16 * NEC_UNIT) 22 #define NECX_HEADER_PULSE (8 * NEC_UNIT) /* Less common NEC variant */ 23 #define NEC_HEADER_SPACE (8 * NEC_UNIT) 24 #define NEC_REPEAT_SPACE (4 * NEC_UNIT) 25 #define NEC_BIT_PULSE (1 * NEC_UNIT) 26 #define NEC_BIT_0_SPACE (1 * NEC_UNIT) 27 #define NEC_BIT_1_SPACE (3 * NEC_UNIT) 28 #define NEC_TRAILER_PULSE (1 * NEC_UNIT) 29 #define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */ 30 #define NECX_REPEAT_BITS 1 31 32 enum nec_state { 33 STATE_INACTIVE, 34 STATE_HEADER_SPACE, 35 STATE_BIT_PULSE, 36 STATE_BIT_SPACE, 37 STATE_TRAILER_PULSE, 38 STATE_TRAILER_SPACE, 39 }; 40 41 /** 42 * ir_nec_decode() - Decode one NEC pulse or space 43 * @dev: the struct rc_dev descriptor of the device 44 * @duration: the struct ir_raw_event descriptor of the pulse/space 45 * 46 * This function returns -EINVAL if the pulse violates the state machine 47 */ 48 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev) 49 { 50 struct nec_dec *data = &dev->raw->nec; 51 u32 scancode; 52 u8 address, not_address, command, not_command; 53 bool send_32bits = false; 54 55 if (!is_timing_event(ev)) { 56 if (ev.reset) 57 data->state = STATE_INACTIVE; 58 return 0; 59 } 60 61 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n", 62 data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 63 64 switch (data->state) { 65 66 case STATE_INACTIVE: 67 if (!ev.pulse) 68 break; 69 70 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) { 71 data->is_nec_x = false; 72 data->necx_repeat = false; 73 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2)) 74 data->is_nec_x = true; 75 else 76 break; 77 78 data->count = 0; 79 data->state = STATE_HEADER_SPACE; 80 return 0; 81 82 case STATE_HEADER_SPACE: 83 if (ev.pulse) 84 break; 85 86 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) { 87 data->state = STATE_BIT_PULSE; 88 return 0; 89 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) { 90 if (!dev->keypressed) { 91 IR_dprintk(1, "Discarding last key repeat: event after key up\n"); 92 } else { 93 rc_repeat(dev); 94 IR_dprintk(1, "Repeat last key\n"); 95 data->state = STATE_TRAILER_PULSE; 96 } 97 return 0; 98 } 99 100 break; 101 102 case STATE_BIT_PULSE: 103 if (!ev.pulse) 104 break; 105 106 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2)) 107 break; 108 109 data->state = STATE_BIT_SPACE; 110 return 0; 111 112 case STATE_BIT_SPACE: 113 if (ev.pulse) 114 break; 115 116 if (data->necx_repeat && data->count == NECX_REPEAT_BITS && 117 geq_margin(ev.duration, 118 NEC_TRAILER_SPACE, NEC_UNIT / 2)) { 119 IR_dprintk(1, "Repeat last key\n"); 120 rc_repeat(dev); 121 data->state = STATE_INACTIVE; 122 return 0; 123 124 } else if (data->count > NECX_REPEAT_BITS) 125 data->necx_repeat = false; 126 127 data->bits <<= 1; 128 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2)) 129 data->bits |= 1; 130 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2)) 131 break; 132 data->count++; 133 134 if (data->count == NEC_NBITS) 135 data->state = STATE_TRAILER_PULSE; 136 else 137 data->state = STATE_BIT_PULSE; 138 139 return 0; 140 141 case STATE_TRAILER_PULSE: 142 if (!ev.pulse) 143 break; 144 145 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2)) 146 break; 147 148 data->state = STATE_TRAILER_SPACE; 149 return 0; 150 151 case STATE_TRAILER_SPACE: 152 if (ev.pulse) 153 break; 154 155 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2)) 156 break; 157 158 address = bitrev8((data->bits >> 24) & 0xff); 159 not_address = bitrev8((data->bits >> 16) & 0xff); 160 command = bitrev8((data->bits >> 8) & 0xff); 161 not_command = bitrev8((data->bits >> 0) & 0xff); 162 163 if ((command ^ not_command) != 0xff) { 164 IR_dprintk(1, "NEC checksum error: received 0x%08x\n", 165 data->bits); 166 send_32bits = true; 167 } 168 169 if (send_32bits) { 170 /* NEC transport, but modified protocol, used by at 171 * least Apple and TiVo remotes */ 172 scancode = data->bits; 173 IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode); 174 } else if ((address ^ not_address) != 0xff) { 175 /* Extended NEC */ 176 scancode = address << 16 | 177 not_address << 8 | 178 command; 179 IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode); 180 } else { 181 /* Normal NEC */ 182 scancode = address << 8 | command; 183 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode); 184 } 185 186 if (data->is_nec_x) 187 data->necx_repeat = true; 188 189 rc_keydown(dev, RC_TYPE_NEC, scancode, 0); 190 data->state = STATE_INACTIVE; 191 return 0; 192 } 193 194 IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n", 195 data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 196 data->state = STATE_INACTIVE; 197 return -EINVAL; 198 } 199 200 static struct ir_raw_handler nec_handler = { 201 .protocols = RC_BIT_NEC, 202 .decode = ir_nec_decode, 203 }; 204 205 static int __init ir_nec_decode_init(void) 206 { 207 ir_raw_handler_register(&nec_handler); 208 209 printk(KERN_INFO "IR NEC protocol handler initialized\n"); 210 return 0; 211 } 212 213 static void __exit ir_nec_decode_exit(void) 214 { 215 ir_raw_handler_unregister(&nec_handler); 216 } 217 218 module_init(ir_nec_decode_init); 219 module_exit(ir_nec_decode_exit); 220 221 MODULE_LICENSE("GPL"); 222 MODULE_AUTHOR("Mauro Carvalho Chehab"); 223 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)"); 224 MODULE_DESCRIPTION("NEC IR protocol decoder"); 225