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 enum rc_type rc_type; 53 u8 address, not_address, command, not_command; 54 bool send_32bits = false; 55 56 if (!is_timing_event(ev)) { 57 if (ev.reset) 58 data->state = STATE_INACTIVE; 59 return 0; 60 } 61 62 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n", 63 data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 64 65 switch (data->state) { 66 67 case STATE_INACTIVE: 68 if (!ev.pulse) 69 break; 70 71 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) { 72 data->is_nec_x = false; 73 data->necx_repeat = false; 74 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2)) 75 data->is_nec_x = true; 76 else 77 break; 78 79 data->count = 0; 80 data->state = STATE_HEADER_SPACE; 81 return 0; 82 83 case STATE_HEADER_SPACE: 84 if (ev.pulse) 85 break; 86 87 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) { 88 data->state = STATE_BIT_PULSE; 89 return 0; 90 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) { 91 if (!dev->keypressed) { 92 IR_dprintk(1, "Discarding last key repeat: event after key up\n"); 93 } else { 94 rc_repeat(dev); 95 IR_dprintk(1, "Repeat last key\n"); 96 data->state = STATE_TRAILER_PULSE; 97 } 98 return 0; 99 } 100 101 break; 102 103 case STATE_BIT_PULSE: 104 if (!ev.pulse) 105 break; 106 107 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2)) 108 break; 109 110 data->state = STATE_BIT_SPACE; 111 return 0; 112 113 case STATE_BIT_SPACE: 114 if (ev.pulse) 115 break; 116 117 if (data->necx_repeat && data->count == NECX_REPEAT_BITS && 118 geq_margin(ev.duration, 119 NEC_TRAILER_SPACE, NEC_UNIT / 2)) { 120 IR_dprintk(1, "Repeat last key\n"); 121 rc_repeat(dev); 122 data->state = STATE_INACTIVE; 123 return 0; 124 125 } else if (data->count > NECX_REPEAT_BITS) 126 data->necx_repeat = false; 127 128 data->bits <<= 1; 129 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2)) 130 data->bits |= 1; 131 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2)) 132 break; 133 data->count++; 134 135 if (data->count == NEC_NBITS) 136 data->state = STATE_TRAILER_PULSE; 137 else 138 data->state = STATE_BIT_PULSE; 139 140 return 0; 141 142 case STATE_TRAILER_PULSE: 143 if (!ev.pulse) 144 break; 145 146 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2)) 147 break; 148 149 data->state = STATE_TRAILER_SPACE; 150 return 0; 151 152 case STATE_TRAILER_SPACE: 153 if (ev.pulse) 154 break; 155 156 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2)) 157 break; 158 159 address = bitrev8((data->bits >> 24) & 0xff); 160 not_address = bitrev8((data->bits >> 16) & 0xff); 161 command = bitrev8((data->bits >> 8) & 0xff); 162 not_command = bitrev8((data->bits >> 0) & 0xff); 163 164 if ((command ^ not_command) != 0xff) { 165 IR_dprintk(1, "NEC checksum error: received 0x%08x\n", 166 data->bits); 167 send_32bits = true; 168 } 169 170 if (send_32bits) { 171 /* NEC transport, but modified protocol, used by at 172 * least Apple and TiVo remotes */ 173 scancode = data->bits; 174 IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode); 175 rc_type = RC_TYPE_NEC32; 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 rc_type = RC_TYPE_NECX; 183 } else { 184 /* Normal NEC */ 185 scancode = address << 8 | command; 186 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode); 187 rc_type = RC_TYPE_NEC; 188 } 189 190 if (data->is_nec_x) 191 data->necx_repeat = true; 192 193 rc_keydown(dev, rc_type, scancode, 0); 194 data->state = STATE_INACTIVE; 195 return 0; 196 } 197 198 IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n", 199 data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 200 data->state = STATE_INACTIVE; 201 return -EINVAL; 202 } 203 204 static struct ir_raw_handler nec_handler = { 205 .protocols = RC_BIT_NEC | RC_BIT_NECX | RC_BIT_NEC32, 206 .decode = ir_nec_decode, 207 }; 208 209 static int __init ir_nec_decode_init(void) 210 { 211 ir_raw_handler_register(&nec_handler); 212 213 printk(KERN_INFO "IR NEC protocol handler initialized\n"); 214 return 0; 215 } 216 217 static void __exit ir_nec_decode_exit(void) 218 { 219 ir_raw_handler_unregister(&nec_handler); 220 } 221 222 module_init(ir_nec_decode_init); 223 module_exit(ir_nec_decode_exit); 224 225 MODULE_LICENSE("GPL"); 226 MODULE_AUTHOR("Mauro Carvalho Chehab"); 227 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)"); 228 MODULE_DESCRIPTION("NEC IR protocol decoder"); 229