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 31 enum 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 */ 47 static 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 } 201 202 static struct ir_raw_handler nec_handler = { 203 .protocols = RC_TYPE_NEC, 204 .decode = ir_nec_decode, 205 }; 206 207 static 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 } 214 215 static void __exit ir_nec_decode_exit(void) 216 { 217 ir_raw_handler_unregister(&nec_handler); 218 } 219 220 module_init(ir_nec_decode_init); 221 module_exit(ir_nec_decode_exit); 222 223 MODULE_LICENSE("GPL"); 224 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>"); 225 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)"); 226 MODULE_DESCRIPTION("NEC IR protocol decoder"); 227