kernel/sound/usb/line6/midibuf.c

   1 /*
   2  * Line 6 Linux USB driver
   3  *
   4  * Copyright (C) 2004-2010 Markus Grabner (grabner@icg.tugraz.at)
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License as
   8  *      published by the Free Software Foundation, version 2.
   9  *
  10  */
  11
  12 #include <linux/slab.h>
  13
  14 #include "midibuf.h"
  15
  16 static int midibuf_message_length(unsigned char code)
  17 {
  18         int message_length;
  19
  20         if (code < 0x80)
  21                 message_length = -1;
  22         else if (code < 0xf0) {
  23                 static const int length[] = { 3, 3, 3, 3, 2, 2, 3 };
  24
  25                 message_length = length[(code >> 4) - 8];
  26         } else {
  27                 /*
  28                    Note that according to the MIDI specification 0xf2 is
  29                    the "Song Position Pointer", but this is used by Line 6
  30                    to send sysex messages to the host.
  31                  */
  32                 static const int length[] = { -1, 2, -1, 2, -1, -1, 1, 1, 1, 1,
  33                         1, 1, 1, -1, 1, 1
  34                 };
  35                 message_length = length[code & 0x0f];
  36         }
  37
  38         return message_length;
  39 }
  40
  41 static int midibuf_is_empty(struct midi_buffer *this)
  42 {
  43         return (this->pos_read == this->pos_write) && !this->full;
  44 }
  45
  46 static int midibuf_is_full(struct midi_buffer *this)
  47 {
  48         return this->full;
  49 }
  50
  51 void line6_midibuf_reset(struct midi_buffer *this)
  52 {
  53         this->pos_read = this->pos_write = this->full = 0;
  54         this->command_prev = -1;
  55 }
  56
  57 int line6_midibuf_init(struct midi_buffer *this, int size, int split)
  58 {
  59         this->buf = kmalloc(size, GFP_KERNEL);
  60
  61         if (this->buf == NULL)
  62                 return -ENOMEM;
  63
  64         this->size = size;
  65         this->split = split;
  66         line6_midibuf_reset(this);
  67         return 0;
  68 }
  69
  70 int line6_midibuf_bytes_free(struct midi_buffer *this)
  71 {
  72         return
  73             midibuf_is_full(this) ?
  74             0 :
  75             (this->pos_read - this->pos_write + this->size - 1) % this->size +
  76             1;
  77 }
  78
  79 int line6_midibuf_bytes_used(struct midi_buffer *this)
  80 {
  81         return
  82             midibuf_is_empty(this) ?
  83             0 :
  84             (this->pos_write - this->pos_read + this->size - 1) % this->size +
  85             1;
  86 }
  87
  88 int line6_midibuf_write(struct midi_buffer *this, unsigned char *data,
  89                         int length)
  90 {
  91         int bytes_free;
  92         int length1, length2;
  93         int skip_active_sense = 0;
  94
  95         if (midibuf_is_full(this) || (length <= 0))
  96                 return 0;
  97
  98         /* skip trailing active sense */
  99         if (data[length - 1] == 0xfe) {
 100                 --length;
 101                 skip_active_sense = 1;
 102         }
 103
 104         bytes_free = line6_midibuf_bytes_free(this);
 105
 106         if (length > bytes_free)
 107                 length = bytes_free;
 108
 109         if (length > 0) {
 110                 length1 = this->size - this->pos_write;
 111
 112                 if (length < length1) {
 113                         /* no buffer wraparound */
 114                         memcpy(this->buf + this->pos_write, data, length);
 115                         this->pos_write += length;
 116                 } else {
 117                         /* buffer wraparound */
 118                         length2 = length - length1;
 119                         memcpy(this->buf + this->pos_write, data, length1);
 120                         memcpy(this->buf, data + length1, length2);
 121                         this->pos_write = length2;
 122                 }
 123
 124                 if (this->pos_write == this->pos_read)
 125                         this->full = 1;
 126         }
 127
 128         return length + skip_active_sense;
 129 }
 130
 131 int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
 132                        int length)
 133 {
 134         int bytes_used;
 135         int length1, length2;
 136         int command;
 137         int midi_length;
 138         int repeat = 0;
 139         int i;
 140
 141         /* we need to be able to store at least a 3 byte MIDI message */
 142         if (length < 3)
 143                 return -EINVAL;
 144
 145         if (midibuf_is_empty(this))
 146                 return 0;
 147
 148         bytes_used = line6_midibuf_bytes_used(this);
 149
 150         if (length > bytes_used)
 151                 length = bytes_used;
 152
 153         length1 = this->size - this->pos_read;
 154
 155         /* check MIDI command length */
 156         command = this->buf[this->pos_read];
 157
 158         if (command & 0x80) {
 159                 midi_length = midibuf_message_length(command);
 160                 this->command_prev = command;
 161         } else {
 162                 if (this->command_prev > 0) {
 163                         int midi_length_prev =
 164                             midibuf_message_length(this->command_prev);
 165
 166                         if (midi_length_prev > 0) {
 167                                 midi_length = midi_length_prev - 1;
 168                                 repeat = 1;
 169                         } else
 170                                 midi_length = -1;
 171                 } else
 172                         midi_length = -1;
 173         }
 174
 175         if (midi_length < 0) {
 176                 /* search for end of message */
 177                 if (length < length1) {
 178                         /* no buffer wraparound */
 179                         for (i = 1; i < length; ++i)
 180                                 if (this->buf[this->pos_read + i] & 0x80)
 181                                         break;
 182
 183                         midi_length = i;
 184                 } else {
 185                         /* buffer wraparound */
 186                         length2 = length - length1;
 187
 188                         for (i = 1; i < length1; ++i)
 189                                 if (this->buf[this->pos_read + i] & 0x80)
 190                                         break;
 191
 192                         if (i < length1)
 193                                 midi_length = i;
 194                         else {
 195                                 for (i = 0; i < length2; ++i)
 196                                         if (this->buf[i] & 0x80)
 197                                                 break;
 198
 199                                 midi_length = length1 + i;
 200                         }
 201                 }
 202
 203                 if (midi_length == length)
 204                         midi_length = -1;       /* end of message not found */
 205         }
 206
 207         if (midi_length < 0) {
 208                 if (!this->split)
 209                         return 0;       /* command is not yet complete */
 210         } else {
 211                 if (length < midi_length)
 212                         return 0;       /* command is not yet complete */
 213
 214                 length = midi_length;
 215         }
 216
 217         if (length < length1) {
 218                 /* no buffer wraparound */
 219                 memcpy(data + repeat, this->buf + this->pos_read, length);
 220                 this->pos_read += length;
 221         } else {
 222                 /* buffer wraparound */
 223                 length2 = length - length1;
 224                 memcpy(data + repeat, this->buf + this->pos_read, length1);
 225                 memcpy(data + repeat + length1, this->buf, length2);
 226                 this->pos_read = length2;
 227         }
 228
 229         if (repeat)
 230                 data[0] = this->command_prev;
 231
 232         this->full = 0;
 233         return length + repeat;
 234 }
 235
 236 int line6_midibuf_ignore(struct midi_buffer *this, int length)
 237 {
 238         int bytes_used = line6_midibuf_bytes_used(this);
 239
 240         if (length > bytes_used)
 241                 length = bytes_used;
 242
 243         this->pos_read = (this->pos_read + length) % this->size;
 244         this->full = 0;
 245         return length;
 246 }
 247
 248 void line6_midibuf_destroy(struct midi_buffer *this)
 249 {
 250         kfree(this->buf);
 251         this->buf = NULL;
 252 }