sound/usb/line6/midibuf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Line 6 Linux USB driver
   4  *
   5  * Copyright (C) 2004-2010 Markus Grabner (grabner@icg.tugraz.at)
   6  */
   7
   8 #include <linux/slab.h>
   9
  10 #include "midibuf.h"
  11
  12 static int midibuf_message_length(unsigned char code)
  13 {
  14         int message_length;
  15
  16         if (code < 0x80)
  17                 message_length = -1;
  18         else if (code < 0xf0) {
  19                 static const int length[] = { 3, 3, 3, 3, 2, 2, 3 };
  20
  21                 message_length = length[(code >> 4) - 8];
  22         } else {
  23                 /*
  24                    Note that according to the MIDI specification 0xf2 is
  25                    the "Song Position Pointer", but this is used by Line 6
  26                    to send sysex messages to the host.
  27                  */
  28                 static const int length[] = { -1, 2, -1, 2, -1, -1, 1, 1, 1, 1,
  29                         1, 1, 1, -1, 1, 1
  30                 };
  31                 message_length = length[code & 0x0f];
  32         }
  33
  34         return message_length;
  35 }
  36
  37 static int midibuf_is_empty(struct midi_buffer *this)
  38 {
  39         return (this->pos_read == this->pos_write) && !this->full;
  40 }
  41
  42 static int midibuf_is_full(struct midi_buffer *this)
  43 {
  44         return this->full;
  45 }
  46
  47 void line6_midibuf_reset(struct midi_buffer *this)
  48 {
  49         this->pos_read = this->pos_write = this->full = 0;
  50         this->command_prev = -1;
  51 }
  52
  53 int line6_midibuf_init(struct midi_buffer *this, int size, int split)
  54 {
  55         this->buf = kmalloc(size, GFP_KERNEL);
  56
  57         if (this->buf == NULL)
  58                 return -ENOMEM;
  59
  60         this->size = size;
  61         this->split = split;
  62         line6_midibuf_reset(this);
  63         return 0;
  64 }
  65
  66 int line6_midibuf_bytes_free(struct midi_buffer *this)
  67 {
  68         return
  69             midibuf_is_full(this) ?
  70             0 :
  71             (this->pos_read - this->pos_write + this->size - 1) % this->size +
  72             1;
  73 }
  74
  75 int line6_midibuf_bytes_used(struct midi_buffer *this)
  76 {
  77         return
  78             midibuf_is_empty(this) ?
  79             0 :
  80             (this->pos_write - this->pos_read + this->size - 1) % this->size +
  81             1;
  82 }
  83
  84 int line6_midibuf_write(struct midi_buffer *this, unsigned char *data,
  85                         int length)
  86 {
  87         int bytes_free;
  88         int length1, length2;
  89         int skip_active_sense = 0;
  90
  91         if (midibuf_is_full(this) || (length <= 0))
  92                 return 0;
  93
  94         /* skip trailing active sense */
  95         if (data[length - 1] == 0xfe) {
  96                 --length;
  97                 skip_active_sense = 1;
  98         }
  99
 100         bytes_free = line6_midibuf_bytes_free(this);
 101
 102         if (length > bytes_free)
 103                 length = bytes_free;
 104
 105         if (length > 0) {
 106                 length1 = this->size - this->pos_write;
 107
 108                 if (length < length1) {
 109                         /* no buffer wraparound */
 110                         memcpy(this->buf + this->pos_write, data, length);
 111                         this->pos_write += length;
 112                 } else {
 113                         /* buffer wraparound */
 114                         length2 = length - length1;
 115                         memcpy(this->buf + this->pos_write, data, length1);
 116                         memcpy(this->buf, data + length1, length2);
 117                         this->pos_write = length2;
 118                 }
 119
 120                 if (this->pos_write == this->pos_read)
 121                         this->full = 1;
 122         }
 123
 124         return length + skip_active_sense;
 125 }
 126
 127 int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
 128                        int length)
 129 {
 130         int bytes_used;
 131         int length1, length2;
 132         int command;
 133         int midi_length;
 134         int repeat = 0;
 135         int i;
 136
 137         /* we need to be able to store at least a 3 byte MIDI message */
 138         if (length < 3)
 139                 return -EINVAL;
 140
 141         if (midibuf_is_empty(this))
 142                 return 0;
 143
 144         bytes_used = line6_midibuf_bytes_used(this);
 145
 146         if (length > bytes_used)
 147                 length = bytes_used;
 148
 149         length1 = this->size - this->pos_read;
 150
 151         /* check MIDI command length */
 152         command = this->buf[this->pos_read];
 153
 154         if (command & 0x80) {
 155                 midi_length = midibuf_message_length(command);
 156                 this->command_prev = command;
 157         } else {
 158                 if (this->command_prev > 0) {
 159                         int midi_length_prev =
 160                             midibuf_message_length(this->command_prev);
 161
 162                         if (midi_length_prev > 1) {
 163                                 midi_length = midi_length_prev - 1;
 164                                 repeat = 1;
 165                         } else
 166                                 midi_length = -1;
 167                 } else
 168                         midi_length = -1;
 169         }
 170
 171         if (midi_length < 0) {
 172                 /* search for end of message */
 173                 if (length < length1) {
 174                         /* no buffer wraparound */
 175                         for (i = 1; i < length; ++i)
 176                                 if (this->buf[this->pos_read + i] & 0x80)
 177                                         break;
 178
 179                         midi_length = i;
 180                 } else {
 181                         /* buffer wraparound */
 182                         length2 = length - length1;
 183
 184                         for (i = 1; i < length1; ++i)
 185                                 if (this->buf[this->pos_read + i] & 0x80)
 186                                         break;
 187
 188                         if (i < length1)
 189                                 midi_length = i;
 190                         else {
 191                                 for (i = 0; i < length2; ++i)
 192                                         if (this->buf[i] & 0x80)
 193                                                 break;
 194
 195                                 midi_length = length1 + i;
 196                         }
 197                 }
 198
 199                 if (midi_length == length)
 200                         midi_length = -1;       /* end of message not found */
 201         }
 202
 203         if (midi_length < 0) {
 204                 if (!this->split)
 205                         return 0;       /* command is not yet complete */
 206         } else {
 207                 if (length < midi_length)
 208                         return 0;       /* command is not yet complete */
 209
 210                 length = midi_length;
 211         }
 212
 213         if (length < length1) {
 214                 /* no buffer wraparound */
 215                 memcpy(data + repeat, this->buf + this->pos_read, length);
 216                 this->pos_read += length;
 217         } else {
 218                 /* buffer wraparound */
 219                 length2 = length - length1;
 220                 memcpy(data + repeat, this->buf + this->pos_read, length1);
 221                 memcpy(data + repeat + length1, this->buf, length2);
 222                 this->pos_read = length2;
 223         }
 224
 225         if (repeat)
 226                 data[0] = this->command_prev;
 227
 228         this->full = 0;
 229         return length + repeat;
 230 }
 231
 232 int line6_midibuf_ignore(struct midi_buffer *this, int length)
 233 {
 234         int bytes_used = line6_midibuf_bytes_used(this);
 235
 236         if (length > bytes_used)
 237                 length = bytes_used;
 238
 239         this->pos_read = (this->pos_read + length) % this->size;
 240         this->full = 0;
 241         return length;
 242 }
 243
 244 void line6_midibuf_destroy(struct midi_buffer *this)
 245 {
 246         kfree(this->buf);
 247         this->buf = NULL;
 248 }