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 
midibuf_message_length(unsigned char code)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 
midibuf_is_empty(struct midi_buffer * this)37 static int midibuf_is_empty(struct midi_buffer *this)
38 {
39 	return (this->pos_read == this->pos_write) && !this->full;
40 }
41 
midibuf_is_full(struct midi_buffer * this)42 static int midibuf_is_full(struct midi_buffer *this)
43 {
44 	return this->full;
45 }
46 
line6_midibuf_reset(struct midi_buffer * this)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 
line6_midibuf_init(struct midi_buffer * this,int size,int split)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 
line6_midibuf_bytes_free(struct midi_buffer * this)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 
line6_midibuf_bytes_used(struct midi_buffer * this)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 
line6_midibuf_write(struct midi_buffer * this,unsigned char * data,int length)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 
line6_midibuf_read(struct midi_buffer * this,unsigned char * data,int length)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 
line6_midibuf_ignore(struct midi_buffer * this,int length)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 
line6_midibuf_destroy(struct midi_buffer * this)244 void line6_midibuf_destroy(struct midi_buffer *this)
245 {
246 	kfree(this->buf);
247 	this->buf = NULL;
248 }
249