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
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(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
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(this->buf);
256	this->buf = NULL;
257}
258