xref: /openbmc/linux/sound/usb/line6/midibuf.c (revision 8508fa2e)
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 
midibuf_message_length(unsigned char code)13 static 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 
midibuf_is_empty(struct midi_buffer * this)33 static int midibuf_is_empty(struct midi_buffer *this)
34 {
35 	return (this->pos_read == this->pos_write) && !this->full;
36 }
37 
midibuf_is_full(struct midi_buffer * this)38 static int midibuf_is_full(struct midi_buffer *this)
39 {
40 	return this->full;
41 }
42 
line6_midibuf_reset(struct midi_buffer * this)43 void 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 
line6_midibuf_init(struct midi_buffer * this,int size,int split)49 int 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 
line6_midibuf_bytes_free(struct midi_buffer * this)62 int 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 
line6_midibuf_bytes_used(struct midi_buffer * this)71 int 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 
line6_midibuf_write(struct midi_buffer * this,unsigned char * data,int length)80 int 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 
line6_midibuf_read(struct midi_buffer * this,unsigned char * data,int length,int read_type)123 int 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(command);
165 		this->command_prev = command;
166 	} else {
167 		if (this->command_prev > 0) {
168 			int midi_length_prev =
169 			    midibuf_message_length(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 
line6_midibuf_ignore(struct midi_buffer * this,int length)241 int 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 
line6_midibuf_destroy(struct midi_buffer * this)253 void line6_midibuf_destroy(struct midi_buffer *this)
254 {
255 	kfree(this->buf);
256 	this->buf = NULL;
257 }
258