1 /* ir-rc5-decoder.c - handle RC5(x) 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 /* 16 * This code handles 14 bits RC5 protocols and 20 bits RC5x protocols. 17 * There are other variants that use a different number of bits. 18 * This is currently unsupported. 19 * It considers a carrier of 36 kHz, with a total of 14/20 bits, where 20 * the first two bits are start bits, and a third one is a filing bit 21 */ 22 23 #include "rc-core-priv.h" 24 25 #define RC5_NBITS 14 26 #define RC5X_NBITS 20 27 #define CHECK_RC5X_NBITS 8 28 #define RC5_UNIT 888888 /* ns */ 29 #define RC5_BIT_START (1 * RC5_UNIT) 30 #define RC5_BIT_END (1 * RC5_UNIT) 31 #define RC5X_SPACE (4 * RC5_UNIT) 32 33 enum rc5_state { 34 STATE_INACTIVE, 35 STATE_BIT_START, 36 STATE_BIT_END, 37 STATE_CHECK_RC5X, 38 STATE_FINISHED, 39 }; 40 41 /** 42 * ir_rc5_decode() - Decode one RC-5 pulse or space 43 * @dev: the struct rc_dev descriptor of the device 44 * @ev: 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_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev) 49 { 50 struct rc5_dec *data = &dev->raw->rc5; 51 u8 toggle; 52 u32 scancode; 53 54 if (!(dev->raw->enabled_protocols & RC_TYPE_RC5)) 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 if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2)) 64 goto out; 65 66 again: 67 IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n", 68 data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 69 70 if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2)) 71 return 0; 72 73 switch (data->state) { 74 75 case STATE_INACTIVE: 76 if (!ev.pulse) 77 break; 78 79 data->state = STATE_BIT_START; 80 data->count = 1; 81 /* We just need enough bits to get to STATE_CHECK_RC5X */ 82 data->wanted_bits = RC5X_NBITS; 83 decrease_duration(&ev, RC5_BIT_START); 84 goto again; 85 86 case STATE_BIT_START: 87 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2)) 88 break; 89 90 data->bits <<= 1; 91 if (!ev.pulse) 92 data->bits |= 1; 93 data->count++; 94 data->state = STATE_BIT_END; 95 return 0; 96 97 case STATE_BIT_END: 98 if (!is_transition(&ev, &dev->raw->prev_ev)) 99 break; 100 101 if (data->count == data->wanted_bits) 102 data->state = STATE_FINISHED; 103 else if (data->count == CHECK_RC5X_NBITS) 104 data->state = STATE_CHECK_RC5X; 105 else 106 data->state = STATE_BIT_START; 107 108 decrease_duration(&ev, RC5_BIT_END); 109 goto again; 110 111 case STATE_CHECK_RC5X: 112 if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) { 113 /* RC5X */ 114 data->wanted_bits = RC5X_NBITS; 115 decrease_duration(&ev, RC5X_SPACE); 116 } else { 117 /* RC5 */ 118 data->wanted_bits = RC5_NBITS; 119 } 120 data->state = STATE_BIT_START; 121 goto again; 122 123 case STATE_FINISHED: 124 if (ev.pulse) 125 break; 126 127 if (data->wanted_bits == RC5X_NBITS) { 128 /* RC5X */ 129 u8 xdata, command, system; 130 xdata = (data->bits & 0x0003F) >> 0; 131 command = (data->bits & 0x00FC0) >> 6; 132 system = (data->bits & 0x1F000) >> 12; 133 toggle = (data->bits & 0x20000) ? 1 : 0; 134 command += (data->bits & 0x01000) ? 0 : 0x40; 135 scancode = system << 16 | command << 8 | xdata; 136 137 IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n", 138 scancode, toggle); 139 140 } else { 141 /* RC5 */ 142 u8 command, system; 143 command = (data->bits & 0x0003F) >> 0; 144 system = (data->bits & 0x007C0) >> 6; 145 toggle = (data->bits & 0x00800) ? 1 : 0; 146 command += (data->bits & 0x01000) ? 0 : 0x40; 147 scancode = system << 8 | command; 148 149 IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n", 150 scancode, toggle); 151 } 152 153 rc_keydown(dev, scancode, toggle); 154 data->state = STATE_INACTIVE; 155 return 0; 156 } 157 158 out: 159 IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n", 160 data->state, TO_US(ev.duration), TO_STR(ev.pulse)); 161 data->state = STATE_INACTIVE; 162 return -EINVAL; 163 } 164 165 static struct ir_raw_handler rc5_handler = { 166 .protocols = RC_TYPE_RC5, 167 .decode = ir_rc5_decode, 168 }; 169 170 static int __init ir_rc5_decode_init(void) 171 { 172 ir_raw_handler_register(&rc5_handler); 173 174 printk(KERN_INFO "IR RC5(x) protocol handler initialized\n"); 175 return 0; 176 } 177 178 static void __exit ir_rc5_decode_exit(void) 179 { 180 ir_raw_handler_unregister(&rc5_handler); 181 } 182 183 module_init(ir_rc5_decode_init); 184 module_exit(ir_rc5_decode_exit); 185 186 MODULE_LICENSE("GPL"); 187 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>"); 188 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)"); 189 MODULE_DESCRIPTION("RC5(x) IR protocol decoder"); 190