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 (!(dev->enabled_protocols & RC_BIT_NEC)) 56 return 0; 57 58 if (!is_timing_event(ev)) { 59 if (ev.reset) 60 data->state = STATE_INACTIVE; 61 return 0; 62 } 63 64 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n", 65 data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 66 67 switch (data->state) { 68 69 case STATE_INACTIVE: 70 if (!ev.pulse) 71 break; 72 73 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) { 74 data->is_nec_x = false; 75 data->necx_repeat = false; 76 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2)) 77 data->is_nec_x = true; 78 else 79 break; 80 81 data->count = 0; 82 data->state = STATE_HEADER_SPACE; 83 return 0; 84 85 case STATE_HEADER_SPACE: 86 if (ev.pulse) 87 break; 88 89 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) { 90 data->state = STATE_BIT_PULSE; 91 return 0; 92 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) { 93 if (!dev->keypressed) { 94 IR_dprintk(1, "Discarding last key repeat: event after key up\n"); 95 } else { 96 rc_repeat(dev); 97 IR_dprintk(1, "Repeat last key\n"); 98 data->state = STATE_TRAILER_PULSE; 99 } 100 return 0; 101 } 102 103 break; 104 105 case STATE_BIT_PULSE: 106 if (!ev.pulse) 107 break; 108 109 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2)) 110 break; 111 112 data->state = STATE_BIT_SPACE; 113 return 0; 114 115 case STATE_BIT_SPACE: 116 if (ev.pulse) 117 break; 118 119 if (data->necx_repeat && data->count == NECX_REPEAT_BITS && 120 geq_margin(ev.duration, 121 NEC_TRAILER_SPACE, NEC_UNIT / 2)) { 122 IR_dprintk(1, "Repeat last key\n"); 123 rc_repeat(dev); 124 data->state = STATE_INACTIVE; 125 return 0; 126 127 } else if (data->count > NECX_REPEAT_BITS) 128 data->necx_repeat = false; 129 130 data->bits <<= 1; 131 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2)) 132 data->bits |= 1; 133 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2)) 134 break; 135 data->count++; 136 137 if (data->count == NEC_NBITS) 138 data->state = STATE_TRAILER_PULSE; 139 else 140 data->state = STATE_BIT_PULSE; 141 142 return 0; 143 144 case STATE_TRAILER_PULSE: 145 if (!ev.pulse) 146 break; 147 148 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2)) 149 break; 150 151 data->state = STATE_TRAILER_SPACE; 152 return 0; 153 154 case STATE_TRAILER_SPACE: 155 if (ev.pulse) 156 break; 157 158 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2)) 159 break; 160 161 address = bitrev8((data->bits >> 24) & 0xff); 162 not_address = bitrev8((data->bits >> 16) & 0xff); 163 command = bitrev8((data->bits >> 8) & 0xff); 164 not_command = bitrev8((data->bits >> 0) & 0xff); 165 166 if ((command ^ not_command) != 0xff) { 167 IR_dprintk(1, "NEC checksum error: received 0x%08x\n", 168 data->bits); 169 send_32bits = true; 170 } 171 172 if (send_32bits) { 173 /* NEC transport, but modified protocol, used by at 174 * least Apple and TiVo remotes */ 175 scancode = data->bits; 176 IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode); 177 } else if ((address ^ not_address) != 0xff) { 178 /* Extended NEC */ 179 scancode = address << 16 | 180 not_address << 8 | 181 command; 182 IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode); 183 } else { 184 /* Normal NEC */ 185 scancode = address << 8 | command; 186 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode); 187 } 188 189 if (data->is_nec_x) 190 data->necx_repeat = true; 191 192 rc_keydown(dev, RC_TYPE_NEC, scancode, 0); 193 data->state = STATE_INACTIVE; 194 return 0; 195 } 196 197 IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n", 198 data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 199 data->state = STATE_INACTIVE; 200 return -EINVAL; 201 } 202 203 static struct ir_raw_handler nec_handler = { 204 .protocols = RC_BIT_NEC, 205 .decode = ir_nec_decode, 206 }; 207 208 static int __init ir_nec_decode_init(void) 209 { 210 ir_raw_handler_register(&nec_handler); 211 212 printk(KERN_INFO "IR NEC protocol handler initialized\n"); 213 return 0; 214 } 215 216 static void __exit ir_nec_decode_exit(void) 217 { 218 ir_raw_handler_unregister(&nec_handler); 219 } 220 221 module_init(ir_nec_decode_init); 222 module_exit(ir_nec_decode_exit); 223 224 MODULE_LICENSE("GPL"); 225 MODULE_AUTHOR("Mauro Carvalho Chehab"); 226 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)"); 227 MODULE_DESCRIPTION("NEC IR protocol decoder"); 228