1/*
  2 * Line6 Linux USB driver - 0.9.1beta
  3 *
  4 * Copyright (C) 2004-2010 Markus Grabner (grabner@icg.tugraz.at)
  5 *
  6 *	This program is free software; you can redistribute it and/or
  7 *	modify it under the terms of the GNU General Public License as
  8 *	published by the Free Software Foundation, version 2.
  9 *
 10 */
 11
 12#include <linux/slab.h>
 13
 14#include "midibuf.h"
 15
 16static int midibuf_message_length(unsigned char code)
 17{
 18	if (code < 0x80)
 19		return -1;
 20	else if (code < 0xf0) {
 21		static const int length[] = { 3, 3, 3, 3, 2, 2, 3 };
 22		return length[(code >> 4) - 8];
 23	} else {
 24		/*
 25		   Note that according to the MIDI specification 0xf2 is
 26		   the "Song Position Pointer", but this is used by Line6
 27		   to send sysex messages to the host.
 28		 */
 29		static const int length[] = { -1, 2, -1, 2, -1, -1, 1, 1, 1, 1,
 30			1, 1, 1, -1, 1, 1
 31		};
 32		return length[code & 0x0f];
 33	}
 34}
 35
 36static int midibuf_is_empty(struct midi_buffer *this)
 37{
 38	return (this->pos_read == this->pos_write) && !this->full;
 39}
 40
 41static int midibuf_is_full(struct midi_buffer *this)
 42{
 43	return this->full;
 44}
 45
 46void line6_midibuf_reset(struct midi_buffer *this)
 47{
 48	this->pos_read = this->pos_write = this->full = 0;
 49	this->command_prev = -1;
 50}
 51
 52int line6_midibuf_init(struct midi_buffer *this, int size, int split)
 53{
 54	this->buf = kmalloc(size, GFP_KERNEL);
 55
 56	if (this->buf == NULL)
 57		return -ENOMEM;
 58
 59	this->size = size;
 60	this->split = split;
 61	line6_midibuf_reset(this);
 62	return 0;
 63}
 64
 65void line6_midibuf_status(struct midi_buffer *this)
 66{
 67	pr_debug("midibuf size=%d split=%d pos_read=%d pos_write=%d full=%d command_prev=%02x\n",
 68		 this->size, this->split, this->pos_read, this->pos_write,
 69		 this->full, this->command_prev);
 70}
 71
 72int line6_midibuf_bytes_free(struct midi_buffer *this)
 73{
 74	return
 75	    midibuf_is_full(this) ?
 76	    0 :
 77	    (this->pos_read - this->pos_write + this->size - 1) % this->size +
 78	    1;
 79}
 80
 81int line6_midibuf_bytes_used(struct midi_buffer *this)
 82{
 83	return
 84	    midibuf_is_empty(this) ?
 85	    0 :
 86	    (this->pos_write - this->pos_read + this->size - 1) % this->size +
 87	    1;
 88}
 89
 90int line6_midibuf_write(struct midi_buffer *this, unsigned char *data,
 91			int length)
 92{
 93	int bytes_free;
 94	int length1, length2;
 95	int skip_active_sense = 0;
 96
 97	if (midibuf_is_full(this) || (length <= 0))
 98		return 0;
 99
100	/* skip trailing active sense */
101	if (data[length - 1] == 0xfe) {
102		--length;
103		skip_active_sense = 1;
104	}
105
106	bytes_free = line6_midibuf_bytes_free(this);
107
108	if (length > bytes_free)
109		length = bytes_free;
110
111	if (length > 0) {
112		length1 = this->size - this->pos_write;
113
114		if (length < length1) {
115			/* no buffer wraparound */
116			memcpy(this->buf + this->pos_write, data, length);
117			this->pos_write += length;
118		} else {
119			/* buffer wraparound */
120			length2 = length - length1;
121			memcpy(this->buf + this->pos_write, data, length1);
122			memcpy(this->buf, data + length1, length2);
123			this->pos_write = length2;
124		}
125
126		if (this->pos_write == this->pos_read)
127			this->full = 1;
128	}
129
130	return length + skip_active_sense;
131}
132
133int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
134		       int length)
135{
136	int bytes_used;
137	int length1, length2;
138	int command;
139	int midi_length;
140	int repeat = 0;
141	int i;
142
143	/* we need to be able to store at least a 3 byte MIDI message */
144	if (length < 3)
145		return -EINVAL;
146
147	if (midibuf_is_empty(this))
148		return 0;
149
150	bytes_used = line6_midibuf_bytes_used(this);
151
152	if (length > bytes_used)
153		length = bytes_used;
154
155	length1 = this->size - this->pos_read;
156
157	/* check MIDI command length */
158	command = this->buf[this->pos_read];
159
160	if (command & 0x80) {
161		midi_length = midibuf_message_length(command);
162		this->command_prev = command;
163	} else {
164		if (this->command_prev > 0) {
165			int midi_length_prev =
166			    midibuf_message_length(this->command_prev);
167
168			if (midi_length_prev > 0) {
169				midi_length = midi_length_prev - 1;
170				repeat = 1;
171			} else
172				midi_length = -1;
173		} else
174			midi_length = -1;
175	}
176
177	if (midi_length < 0) {
178		/* search for end of message */
179		if (length < length1) {
180			/* no buffer wraparound */
181			for (i = 1; i < length; ++i)
182				if (this->buf[this->pos_read + i] & 0x80)
183					break;
184
185			midi_length = i;
186		} else {
187			/* buffer wraparound */
188			length2 = length - length1;
189
190			for (i = 1; i < length1; ++i)
191				if (this->buf[this->pos_read + i] & 0x80)
192					break;
193
194			if (i < length1)
195				midi_length = i;
196			else {
197				for (i = 0; i < length2; ++i)
198					if (this->buf[i] & 0x80)
199						break;
200
201				midi_length = length1 + i;
202			}
203		}
204
205		if (midi_length == length)
206			midi_length = -1;	/* end of message not found */
207	}
208
209	if (midi_length < 0) {
210		if (!this->split)
211			return 0;	/* command is not yet complete */
212	} else {
213		if (length < midi_length)
214			return 0;	/* command is not yet complete */
215
216		length = midi_length;
217	}
218
219	if (length < length1) {
220		/* no buffer wraparound */
221		memcpy(data + repeat, this->buf + this->pos_read, length);
222		this->pos_read += length;
223	} else {
224		/* buffer wraparound */
225		length2 = length - length1;
226		memcpy(data + repeat, this->buf + this->pos_read, length1);
227		memcpy(data + repeat + length1, this->buf, length2);
228		this->pos_read = length2;
229	}
230
231	if (repeat)
232		data[0] = this->command_prev;
233
234	this->full = 0;
235	return length + repeat;
236}
237
238int line6_midibuf_ignore(struct midi_buffer *this, int length)
239{
240	int bytes_used = line6_midibuf_bytes_used(this);
241
242	if (length > bytes_used)
243		length = bytes_used;
244
245	this->pos_read = (this->pos_read + length) % this->size;
246	this->full = 0;
247	return length;
248}
249
250int line6_midibuf_skip_message(struct midi_buffer *this, unsigned short mask)
251{
252	int cmd = this->command_prev;
253
254	if ((cmd >= 0x80) && (cmd < 0xf0))
255		if ((mask & (1 << (cmd & 0x0f))) == 0)
256			return 1;
257
258	return 0;
259}
260
261void line6_midibuf_destroy(struct midi_buffer *this)
262{
263	kfree(this->buf);
264	this->buf = NULL;
265}