1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Line 6 Linux USB driver
4 *
5 * Copyright (C) 2004-2010 Markus Grabner (line6@grabner-graz.at)
6 */
7
8#include <linux/slab.h>
9
10#include "midibuf.h"
11
12
13static int midibuf_message_length(unsigned char code)
14{
15 int message_length;
16
17 if (code < 0x80)
18 message_length = -1;
19 else if (code < 0xf0) {
20 static const int length[] = { 3, 3, 3, 3, 2, 2, 3 };
21
22 message_length = length[(code >> 4) - 8];
23 } else {
24 static const int length[] = { -1, 2, 2, 2, -1, -1, 1, 1, 1, -1,
25 1, 1, 1, -1, 1, 1
26 };
27 message_length = length[code & 0x0f];
28 }
29
30 return message_length;
31}
32
33static int midibuf_is_empty(struct midi_buffer *this)
34{
35 return (this->pos_read == this->pos_write) && !this->full;
36}
37
38static int midibuf_is_full(struct midi_buffer *this)
39{
40 return this->full;
41}
42
43void line6_midibuf_reset(struct midi_buffer *this)
44{
45 this->pos_read = this->pos_write = this->full = 0;
46 this->command_prev = -1;
47}
48
49int line6_midibuf_init(struct midi_buffer *this, int size, int split)
50{
51 this->buf = kmalloc(size, GFP_KERNEL);
52
53 if (this->buf == NULL)
54 return -ENOMEM;
55
56 this->size = size;
57 this->split = split;
58 line6_midibuf_reset(this);
59 return 0;
60}
61
62int line6_midibuf_bytes_free(struct midi_buffer *this)
63{
64 return
65 midibuf_is_full(this) ?
66 0 :
67 (this->pos_read - this->pos_write + this->size - 1) % this->size +
68 1;
69}
70
71int line6_midibuf_bytes_used(struct midi_buffer *this)
72{
73 return
74 midibuf_is_empty(this) ?
75 0 :
76 (this->pos_write - this->pos_read + this->size - 1) % this->size +
77 1;
78}
79
80int line6_midibuf_write(struct midi_buffer *this, unsigned char *data,
81 int length)
82{
83 int bytes_free;
84 int length1, length2;
85 int skip_active_sense = 0;
86
87 if (midibuf_is_full(this) || (length <= 0))
88 return 0;
89
90 /* skip trailing active sense */
91 if (data[length - 1] == 0xfe) {
92 --length;
93 skip_active_sense = 1;
94 }
95
96 bytes_free = line6_midibuf_bytes_free(this);
97
98 if (length > bytes_free)
99 length = bytes_free;
100
101 if (length > 0) {
102 length1 = this->size - this->pos_write;
103
104 if (length < length1) {
105 /* no buffer wraparound */
106 memcpy(this->buf + this->pos_write, data, length);
107 this->pos_write += length;
108 } else {
109 /* buffer wraparound */
110 length2 = length - length1;
111 memcpy(this->buf + this->pos_write, data, length1);
112 memcpy(this->buf, data + length1, length2);
113 this->pos_write = length2;
114 }
115
116 if (this->pos_write == this->pos_read)
117 this->full = 1;
118 }
119
120 return length + skip_active_sense;
121}
122
123int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
124 int length, int read_type)
125{
126 int bytes_used;
127 int length1, length2;
128 int command;
129 int midi_length;
130 int repeat = 0;
131 int i;
132
133 /* we need to be able to store at least a 3 byte MIDI message */
134 if (length < 3)
135 return -EINVAL;
136
137 if (midibuf_is_empty(this))
138 return 0;
139
140 bytes_used = line6_midibuf_bytes_used(this);
141
142 if (length > bytes_used)
143 length = bytes_used;
144
145 length1 = this->size - this->pos_read;
146
147 command = this->buf[this->pos_read];
148 /*
149 PODxt always has status byte lower nibble set to 0010,
150 when it means to send 0000, so we correct if here so
151 that control/program changes come on channel 1 and
152 sysex message status byte is correct
153 */
154 if (read_type == LINE6_MIDIBUF_READ_RX) {
155 if (command == 0xb2 || command == 0xc2 || command == 0xf2) {
156 unsigned char fixed = command & 0xf0;
157 this->buf[this->pos_read] = fixed;
158 command = fixed;
159 }
160 }
161
162 /* check MIDI command length */
163 if (command & 0x80) {
164 midi_length = midibuf_message_length(code: command);
165 this->command_prev = command;
166 } else {
167 if (this->command_prev > 0) {
168 int midi_length_prev =
169 midibuf_message_length(code: this->command_prev);
170
171 if (midi_length_prev > 1) {
172 midi_length = midi_length_prev - 1;
173 repeat = 1;
174 } else
175 midi_length = -1;
176 } else
177 midi_length = -1;
178 }
179
180 if (midi_length < 0) {
181 /* search for end of message */
182 if (length < length1) {
183 /* no buffer wraparound */
184 for (i = 1; i < length; ++i)
185 if (this->buf[this->pos_read + i] & 0x80)
186 break;
187
188 midi_length = i;
189 } else {
190 /* buffer wraparound */
191 length2 = length - length1;
192
193 for (i = 1; i < length1; ++i)
194 if (this->buf[this->pos_read + i] & 0x80)
195 break;
196
197 if (i < length1)
198 midi_length = i;
199 else {
200 for (i = 0; i < length2; ++i)
201 if (this->buf[i] & 0x80)
202 break;
203
204 midi_length = length1 + i;
205 }
206 }
207
208 if (midi_length == length)
209 midi_length = -1; /* end of message not found */
210 }
211
212 if (midi_length < 0) {
213 if (!this->split)
214 return 0; /* command is not yet complete */
215 } else {
216 if (length < midi_length)
217 return 0; /* command is not yet complete */
218
219 length = midi_length;
220 }
221
222 if (length < length1) {
223 /* no buffer wraparound */
224 memcpy(data + repeat, this->buf + this->pos_read, length);
225 this->pos_read += length;
226 } else {
227 /* buffer wraparound */
228 length2 = length - length1;
229 memcpy(data + repeat, this->buf + this->pos_read, length1);
230 memcpy(data + repeat + length1, this->buf, length2);
231 this->pos_read = length2;
232 }
233
234 if (repeat)
235 data[0] = this->command_prev;
236
237 this->full = 0;
238 return length + repeat;
239}
240
241int line6_midibuf_ignore(struct midi_buffer *this, int length)
242{
243 int bytes_used = line6_midibuf_bytes_used(this);
244
245 if (length > bytes_used)
246 length = bytes_used;
247
248 this->pos_read = (this->pos_read + length) % this->size;
249 this->full = 0;
250 return length;
251}
252
253void line6_midibuf_destroy(struct midi_buffer *this)
254{
255 kfree(objp: this->buf);
256 this->buf = NULL;
257}
258

source code of linux/sound/usb/line6/midibuf.c