1 /*
2  *  Copyright (c) by Jaroslav Kysela <perex@suse.cz>
3  *  Routines for control of MPU-401 in UART mode
4  *
5  *  MPU-401 supports UART mode which is not capable generate transmit
6  *  interrupts thus output is done via polling. Also, if irq < 0, then
7  *  input is done also via polling. Do not expect good performance.
8  *
9  *
10  *   This program is free software; you can redistribute it and/or modify
11  *   it under the terms of the GNU General Public License as published by
12  *   the Free Software Foundation; either version 2 of the License, or
13  *   (at your option) any later version.
14  *
15  *   This program is distributed in the hope that it will be useful,
16  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
17  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18  *   GNU General Public License for more details.
19  *
20  *   You should have received a copy of the GNU General Public License
21  *   along with this program; if not, write to the Free Software
22  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
23  *
24  *   13-03-2003:
25  *      Added support for different kind of hardware I/O. Build in choices
26  *      are port and mmio. For other kind of I/O, set mpu->read and
27  *      mpu->write to your own I/O functions.
28  *
29  */
30 
31 #include <sound/driver.h>
32 #include <asm/io.h>
33 #include <linux/delay.h>
34 #include <linux/init.h>
35 #include <linux/slab.h>
36 #include <linux/ioport.h>
37 #include <linux/interrupt.h>
38 #include <linux/errno.h>
39 #include <sound/core.h>
40 #include <sound/mpu401.h>
41 
42 MODULE_AUTHOR("Jaroslav Kysela <perex@suse.cz>");
43 MODULE_DESCRIPTION("Routines for control of MPU-401 in UART mode");
44 MODULE_LICENSE("GPL");
45 
46 static void snd_mpu401_uart_input_read(struct snd_mpu401 * mpu);
47 static void snd_mpu401_uart_output_write(struct snd_mpu401 * mpu);
48 
49 /*
50 
51  */
52 
53 #define snd_mpu401_input_avail(mpu)	(!(mpu->read(mpu, MPU401C(mpu)) & 0x80))
54 #define snd_mpu401_output_ready(mpu)	(!(mpu->read(mpu, MPU401C(mpu)) & 0x40))
55 
56 #define MPU401_RESET		0xff
57 #define MPU401_ENTER_UART	0x3f
58 #define MPU401_ACK		0xfe
59 
60 /* Build in lowlevel io */
61 static void mpu401_write_port(struct snd_mpu401 *mpu, unsigned char data,
62 			      unsigned long addr)
63 {
64 	outb(data, addr);
65 }
66 
67 static unsigned char mpu401_read_port(struct snd_mpu401 *mpu,
68 				      unsigned long addr)
69 {
70 	return inb(addr);
71 }
72 
73 static void mpu401_write_mmio(struct snd_mpu401 *mpu, unsigned char data,
74 			      unsigned long addr)
75 {
76 	writeb(data, (void __iomem *)addr);
77 }
78 
79 static unsigned char mpu401_read_mmio(struct snd_mpu401 *mpu,
80 				      unsigned long addr)
81 {
82 	return readb((void __iomem *)addr);
83 }
84 /*  */
85 
86 static void snd_mpu401_uart_clear_rx(struct snd_mpu401 *mpu)
87 {
88 	int timeout = 100000;
89 	for (; timeout > 0 && snd_mpu401_input_avail(mpu); timeout--)
90 		mpu->read(mpu, MPU401D(mpu));
91 #ifdef CONFIG_SND_DEBUG
92 	if (timeout <= 0)
93 		snd_printk(KERN_ERR "cmd: clear rx timeout (status = 0x%x)\n",
94 			   mpu->read(mpu, MPU401C(mpu)));
95 #endif
96 }
97 
98 static void uart_interrupt_tx(struct snd_mpu401 *mpu)
99 {
100 	if (test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode) &&
101 	    test_bit(MPU401_MODE_BIT_OUTPUT_TRIGGER, &mpu->mode)) {
102 		spin_lock(&mpu->output_lock);
103 		snd_mpu401_uart_output_write(mpu);
104 		spin_unlock(&mpu->output_lock);
105 	}
106 }
107 
108 static void _snd_mpu401_uart_interrupt(struct snd_mpu401 *mpu)
109 {
110 	if (mpu->info_flags & MPU401_INFO_INPUT) {
111 		spin_lock(&mpu->input_lock);
112 		if (test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode))
113 			snd_mpu401_uart_input_read(mpu);
114 		else
115 			snd_mpu401_uart_clear_rx(mpu);
116 		spin_unlock(&mpu->input_lock);
117 	}
118 	if (! (mpu->info_flags & MPU401_INFO_TX_IRQ))
119 		/* ok. for better Tx performance try do some output
120 		   when input is done */
121 		uart_interrupt_tx(mpu);
122 }
123 
124 /**
125  * snd_mpu401_uart_interrupt - generic MPU401-UART interrupt handler
126  * @irq: the irq number
127  * @dev_id: mpu401 instance
128  *
129  * Processes the interrupt for MPU401-UART i/o.
130  */
131 irqreturn_t snd_mpu401_uart_interrupt(int irq, void *dev_id)
132 {
133 	struct snd_mpu401 *mpu = dev_id;
134 
135 	if (mpu == NULL)
136 		return IRQ_NONE;
137 	_snd_mpu401_uart_interrupt(mpu);
138 	return IRQ_HANDLED;
139 }
140 
141 EXPORT_SYMBOL(snd_mpu401_uart_interrupt);
142 
143 /**
144  * snd_mpu401_uart_interrupt_tx - generic MPU401-UART transmit irq handler
145  * @irq: the irq number
146  * @dev_id: mpu401 instance
147  *
148  * Processes the interrupt for MPU401-UART output.
149  */
150 irqreturn_t snd_mpu401_uart_interrupt_tx(int irq, void *dev_id)
151 {
152 	struct snd_mpu401 *mpu = dev_id;
153 
154 	if (mpu == NULL)
155 		return IRQ_NONE;
156 	uart_interrupt_tx(mpu);
157 	return IRQ_HANDLED;
158 }
159 
160 EXPORT_SYMBOL(snd_mpu401_uart_interrupt_tx);
161 
162 /*
163  * timer callback
164  * reprogram the timer and call the interrupt job
165  */
166 static void snd_mpu401_uart_timer(unsigned long data)
167 {
168 	struct snd_mpu401 *mpu = (struct snd_mpu401 *)data;
169 	unsigned long flags;
170 
171 	spin_lock_irqsave(&mpu->timer_lock, flags);
172 	/*mpu->mode |= MPU401_MODE_TIMER;*/
173 	mpu->timer.expires = 1 + jiffies;
174 	add_timer(&mpu->timer);
175 	spin_unlock_irqrestore(&mpu->timer_lock, flags);
176 	if (mpu->rmidi)
177 		_snd_mpu401_uart_interrupt(mpu);
178 }
179 
180 /*
181  * initialize the timer callback if not programmed yet
182  */
183 static void snd_mpu401_uart_add_timer (struct snd_mpu401 *mpu, int input)
184 {
185 	unsigned long flags;
186 
187 	spin_lock_irqsave (&mpu->timer_lock, flags);
188 	if (mpu->timer_invoked == 0) {
189 		init_timer(&mpu->timer);
190 		mpu->timer.data = (unsigned long)mpu;
191 		mpu->timer.function = snd_mpu401_uart_timer;
192 		mpu->timer.expires = 1 + jiffies;
193 		add_timer(&mpu->timer);
194 	}
195 	mpu->timer_invoked |= input ? MPU401_MODE_INPUT_TIMER :
196 		MPU401_MODE_OUTPUT_TIMER;
197 	spin_unlock_irqrestore (&mpu->timer_lock, flags);
198 }
199 
200 /*
201  * remove the timer callback if still active
202  */
203 static void snd_mpu401_uart_remove_timer (struct snd_mpu401 *mpu, int input)
204 {
205 	unsigned long flags;
206 
207 	spin_lock_irqsave (&mpu->timer_lock, flags);
208 	if (mpu->timer_invoked) {
209 		mpu->timer_invoked &= input ? ~MPU401_MODE_INPUT_TIMER :
210 			~MPU401_MODE_OUTPUT_TIMER;
211 		if (! mpu->timer_invoked)
212 			del_timer(&mpu->timer);
213 	}
214 	spin_unlock_irqrestore (&mpu->timer_lock, flags);
215 }
216 
217 /*
218  * send a UART command
219  * return zero if successful, non-zero for some errors
220  */
221 
222 static int snd_mpu401_uart_cmd(struct snd_mpu401 * mpu, unsigned char cmd,
223 			       int ack)
224 {
225 	unsigned long flags;
226 	int timeout, ok;
227 
228 	spin_lock_irqsave(&mpu->input_lock, flags);
229 	if (mpu->hardware != MPU401_HW_TRID4DWAVE) {
230 		mpu->write(mpu, 0x00, MPU401D(mpu));
231 		/*snd_mpu401_uart_clear_rx(mpu);*/
232 	}
233 	/* ok. standard MPU-401 initialization */
234 	if (mpu->hardware != MPU401_HW_SB) {
235 		for (timeout = 1000; timeout > 0 &&
236 			     !snd_mpu401_output_ready(mpu); timeout--)
237 			udelay(10);
238 #ifdef CONFIG_SND_DEBUG
239 		if (!timeout)
240 			snd_printk(KERN_ERR "cmd: tx timeout (status = 0x%x)\n",
241 				   mpu->read(mpu, MPU401C(mpu)));
242 #endif
243 	}
244 	mpu->write(mpu, cmd, MPU401C(mpu));
245 	if (ack) {
246 		ok = 0;
247 		timeout = 10000;
248 		while (!ok && timeout-- > 0) {
249 			if (snd_mpu401_input_avail(mpu)) {
250 				if (mpu->read(mpu, MPU401D(mpu)) == MPU401_ACK)
251 					ok = 1;
252 			}
253 		}
254 		if (!ok && mpu->read(mpu, MPU401D(mpu)) == MPU401_ACK)
255 			ok = 1;
256 	} else
257 		ok = 1;
258 	spin_unlock_irqrestore(&mpu->input_lock, flags);
259 	if (!ok) {
260 		snd_printk(KERN_ERR "cmd: 0x%x failed at 0x%lx "
261 			   "(status = 0x%x, data = 0x%x)\n", cmd, mpu->port,
262 			   mpu->read(mpu, MPU401C(mpu)),
263 			   mpu->read(mpu, MPU401D(mpu)));
264 		return 1;
265 	}
266 	return 0;
267 }
268 
269 static int snd_mpu401_do_reset(struct snd_mpu401 *mpu)
270 {
271 	if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
272 		return -EIO;
273 	if (!(mpu->info_flags & MPU401_INFO_UART_ONLY) &&
274 	    snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
275 		return -EIO;
276 	return 0;
277 }
278 
279 /*
280  * input/output open/close - protected by open_mutex in rawmidi.c
281  */
282 static int snd_mpu401_uart_input_open(struct snd_rawmidi_substream *substream)
283 {
284 	struct snd_mpu401 *mpu;
285 	int err;
286 
287 	mpu = substream->rmidi->private_data;
288 	if (mpu->open_input && (err = mpu->open_input(mpu)) < 0)
289 		return err;
290 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode)) {
291 		if (snd_mpu401_do_reset(mpu) < 0)
292 			goto error_out;
293 	}
294 	mpu->substream_input = substream;
295 	set_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
296 	return 0;
297 
298 error_out:
299 	if (mpu->open_input && mpu->close_input)
300 		mpu->close_input(mpu);
301 	return -EIO;
302 }
303 
304 static int snd_mpu401_uart_output_open(struct snd_rawmidi_substream *substream)
305 {
306 	struct snd_mpu401 *mpu;
307 	int err;
308 
309 	mpu = substream->rmidi->private_data;
310 	if (mpu->open_output && (err = mpu->open_output(mpu)) < 0)
311 		return err;
312 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode)) {
313 		if (snd_mpu401_do_reset(mpu) < 0)
314 			goto error_out;
315 	}
316 	mpu->substream_output = substream;
317 	set_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
318 	return 0;
319 
320 error_out:
321 	if (mpu->open_output && mpu->close_output)
322 		mpu->close_output(mpu);
323 	return -EIO;
324 }
325 
326 static int snd_mpu401_uart_input_close(struct snd_rawmidi_substream *substream)
327 {
328 	struct snd_mpu401 *mpu;
329 	int err = 0;
330 
331 	mpu = substream->rmidi->private_data;
332 	clear_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
333 	mpu->substream_input = NULL;
334 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode))
335 		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
336 	if (mpu->close_input)
337 		mpu->close_input(mpu);
338 	if (err)
339 		return -EIO;
340 	return 0;
341 }
342 
343 static int snd_mpu401_uart_output_close(struct snd_rawmidi_substream *substream)
344 {
345 	struct snd_mpu401 *mpu;
346 	int err = 0;
347 
348 	mpu = substream->rmidi->private_data;
349 	clear_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
350 	mpu->substream_output = NULL;
351 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode))
352 		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
353 	if (mpu->close_output)
354 		mpu->close_output(mpu);
355 	if (err)
356 		return -EIO;
357 	return 0;
358 }
359 
360 /*
361  * trigger input callback
362  */
363 static void
364 snd_mpu401_uart_input_trigger(struct snd_rawmidi_substream *substream, int up)
365 {
366 	unsigned long flags;
367 	struct snd_mpu401 *mpu;
368 	int max = 64;
369 
370 	mpu = substream->rmidi->private_data;
371 	if (up) {
372 		if (! test_and_set_bit(MPU401_MODE_BIT_INPUT_TRIGGER,
373 				       &mpu->mode)) {
374 			/* first time - flush FIFO */
375 			while (max-- > 0)
376 				mpu->read(mpu, MPU401D(mpu));
377 			if (mpu->irq < 0)
378 				snd_mpu401_uart_add_timer(mpu, 1);
379 		}
380 
381 		/* read data in advance */
382 		spin_lock_irqsave(&mpu->input_lock, flags);
383 		snd_mpu401_uart_input_read(mpu);
384 		spin_unlock_irqrestore(&mpu->input_lock, flags);
385 	} else {
386 		if (mpu->irq < 0)
387 			snd_mpu401_uart_remove_timer(mpu, 1);
388 		clear_bit(MPU401_MODE_BIT_INPUT_TRIGGER, &mpu->mode);
389 	}
390 
391 }
392 
393 /*
394  * transfer input pending data
395  * call with input_lock spinlock held
396  */
397 static void snd_mpu401_uart_input_read(struct snd_mpu401 * mpu)
398 {
399 	int max = 128;
400 	unsigned char byte;
401 
402 	while (max-- > 0) {
403 		if (! snd_mpu401_input_avail(mpu))
404 			break; /* input not available */
405 		byte = mpu->read(mpu, MPU401D(mpu));
406 		if (test_bit(MPU401_MODE_BIT_INPUT_TRIGGER, &mpu->mode))
407 			snd_rawmidi_receive(mpu->substream_input, &byte, 1);
408 	}
409 }
410 
411 /*
412  *  Tx FIFO sizes:
413  *    CS4237B			- 16 bytes
414  *    AudioDrive ES1688         - 12 bytes
415  *    S3 SonicVibes             -  8 bytes
416  *    SoundBlaster AWE 64       -  2 bytes (ugly hardware)
417  */
418 
419 /*
420  * write output pending bytes
421  * call with output_lock spinlock held
422  */
423 static void snd_mpu401_uart_output_write(struct snd_mpu401 * mpu)
424 {
425 	unsigned char byte;
426 	int max = 256, timeout;
427 
428 	do {
429 		if (snd_rawmidi_transmit_peek(mpu->substream_output,
430 					      &byte, 1) == 1) {
431 			for (timeout = 100; timeout > 0; timeout--) {
432 				if (snd_mpu401_output_ready(mpu))
433 					break;
434 			}
435 			if (timeout == 0)
436 				break;	/* Tx FIFO full - try again later */
437 			mpu->write(mpu, byte, MPU401D(mpu));
438 			snd_rawmidi_transmit_ack(mpu->substream_output, 1);
439 		} else {
440 			snd_mpu401_uart_remove_timer (mpu, 0);
441 			break;	/* no other data - leave the tx loop */
442 		}
443 	} while (--max > 0);
444 }
445 
446 /*
447  * output trigger callback
448  */
449 static void
450 snd_mpu401_uart_output_trigger(struct snd_rawmidi_substream *substream, int up)
451 {
452 	unsigned long flags;
453 	struct snd_mpu401 *mpu;
454 
455 	mpu = substream->rmidi->private_data;
456 	if (up) {
457 		set_bit(MPU401_MODE_BIT_OUTPUT_TRIGGER, &mpu->mode);
458 
459 		/* try to add the timer at each output trigger,
460 		 * since the output timer might have been removed in
461 		 * snd_mpu401_uart_output_write().
462 		 */
463 		if (! (mpu->info_flags & MPU401_INFO_TX_IRQ))
464 			snd_mpu401_uart_add_timer(mpu, 0);
465 
466 		/* output pending data */
467 		spin_lock_irqsave(&mpu->output_lock, flags);
468 		snd_mpu401_uart_output_write(mpu);
469 		spin_unlock_irqrestore(&mpu->output_lock, flags);
470 	} else {
471 		if (! (mpu->info_flags & MPU401_INFO_TX_IRQ))
472 			snd_mpu401_uart_remove_timer(mpu, 0);
473 		clear_bit(MPU401_MODE_BIT_OUTPUT_TRIGGER, &mpu->mode);
474 	}
475 }
476 
477 /*
478 
479  */
480 
481 static struct snd_rawmidi_ops snd_mpu401_uart_output =
482 {
483 	.open =		snd_mpu401_uart_output_open,
484 	.close =	snd_mpu401_uart_output_close,
485 	.trigger =	snd_mpu401_uart_output_trigger,
486 };
487 
488 static struct snd_rawmidi_ops snd_mpu401_uart_input =
489 {
490 	.open =		snd_mpu401_uart_input_open,
491 	.close =	snd_mpu401_uart_input_close,
492 	.trigger =	snd_mpu401_uart_input_trigger,
493 };
494 
495 static void snd_mpu401_uart_free(struct snd_rawmidi *rmidi)
496 {
497 	struct snd_mpu401 *mpu = rmidi->private_data;
498 	if (mpu->irq_flags && mpu->irq >= 0)
499 		free_irq(mpu->irq, (void *) mpu);
500 	release_and_free_resource(mpu->res);
501 	kfree(mpu);
502 }
503 
504 /**
505  * snd_mpu401_uart_new - create an MPU401-UART instance
506  * @card: the card instance
507  * @device: the device index, zero-based
508  * @hardware: the hardware type, MPU401_HW_XXXX
509  * @port: the base address of MPU401 port
510  * @info_flags: bitflags MPU401_INFO_XXX
511  * @irq: the irq number, -1 if no interrupt for mpu
512  * @irq_flags: the irq request flags (SA_XXX), 0 if irq was already reserved.
513  * @rrawmidi: the pointer to store the new rawmidi instance
514  *
515  * Creates a new MPU-401 instance.
516  *
517  * Note that the rawmidi instance is returned on the rrawmidi argument,
518  * not the mpu401 instance itself.  To access to the mpu401 instance,
519  * cast from rawmidi->private_data (with struct snd_mpu401 magic-cast).
520  *
521  * Returns zero if successful, or a negative error code.
522  */
523 int snd_mpu401_uart_new(struct snd_card *card, int device,
524 			unsigned short hardware,
525 			unsigned long port,
526 			unsigned int info_flags,
527 			int irq, int irq_flags,
528 			struct snd_rawmidi ** rrawmidi)
529 {
530 	struct snd_mpu401 *mpu;
531 	struct snd_rawmidi *rmidi;
532 	int in_enable, out_enable;
533 	int err;
534 
535 	if (rrawmidi)
536 		*rrawmidi = NULL;
537 	if (! (info_flags & (MPU401_INFO_INPUT | MPU401_INFO_OUTPUT)))
538 		info_flags |= MPU401_INFO_INPUT | MPU401_INFO_OUTPUT;
539 	in_enable = (info_flags & MPU401_INFO_INPUT) ? 1 : 0;
540 	out_enable = (info_flags & MPU401_INFO_OUTPUT) ? 1 : 0;
541 	if ((err = snd_rawmidi_new(card, "MPU-401U", device,
542 				   out_enable, in_enable, &rmidi)) < 0)
543 		return err;
544 	mpu = kzalloc(sizeof(*mpu), GFP_KERNEL);
545 	if (mpu == NULL) {
546 		snd_printk(KERN_ERR "mpu401_uart: cannot allocate\n");
547 		snd_device_free(card, rmidi);
548 		return -ENOMEM;
549 	}
550 	rmidi->private_data = mpu;
551 	rmidi->private_free = snd_mpu401_uart_free;
552 	spin_lock_init(&mpu->input_lock);
553 	spin_lock_init(&mpu->output_lock);
554 	spin_lock_init(&mpu->timer_lock);
555 	mpu->hardware = hardware;
556 	if (! (info_flags & MPU401_INFO_INTEGRATED)) {
557 		int res_size = hardware == MPU401_HW_PC98II ? 4 : 2;
558 		mpu->res = request_region(port, res_size, "MPU401 UART");
559 		if (mpu->res == NULL) {
560 			snd_printk(KERN_ERR "mpu401_uart: "
561 				   "unable to grab port 0x%lx size %d\n",
562 				   port, res_size);
563 			snd_device_free(card, rmidi);
564 			return -EBUSY;
565 		}
566 	}
567 	if (info_flags & MPU401_INFO_MMIO) {
568 		mpu->write = mpu401_write_mmio;
569 		mpu->read = mpu401_read_mmio;
570 	} else {
571 		mpu->write = mpu401_write_port;
572 		mpu->read = mpu401_read_port;
573 	}
574 	mpu->port = port;
575 	if (hardware == MPU401_HW_PC98II)
576 		mpu->cport = port + 2;
577 	else
578 		mpu->cport = port + 1;
579 	if (irq >= 0 && irq_flags) {
580 		if (request_irq(irq, snd_mpu401_uart_interrupt, irq_flags,
581 				"MPU401 UART", (void *) mpu)) {
582 			snd_printk(KERN_ERR "mpu401_uart: "
583 				   "unable to grab IRQ %d\n", irq);
584 			snd_device_free(card, rmidi);
585 			return -EBUSY;
586 		}
587 	}
588 	mpu->info_flags = info_flags;
589 	mpu->irq = irq;
590 	mpu->irq_flags = irq_flags;
591 	if (card->shortname[0])
592 		snprintf(rmidi->name, sizeof(rmidi->name), "%s MIDI",
593 			 card->shortname);
594 	else
595 		sprintf(rmidi->name, "MPU-401 MIDI %d-%d",card->number, device);
596 	if (out_enable) {
597 		snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
598 				    &snd_mpu401_uart_output);
599 		rmidi->info_flags |= SNDRV_RAWMIDI_INFO_OUTPUT;
600 	}
601 	if (in_enable) {
602 		snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT,
603 				    &snd_mpu401_uart_input);
604 		rmidi->info_flags |= SNDRV_RAWMIDI_INFO_INPUT;
605 		if (out_enable)
606 			rmidi->info_flags |= SNDRV_RAWMIDI_INFO_DUPLEX;
607 	}
608 	mpu->rmidi = rmidi;
609 	if (rrawmidi)
610 		*rrawmidi = rmidi;
611 	return 0;
612 }
613 
614 EXPORT_SYMBOL(snd_mpu401_uart_new);
615 
616 /*
617  *  INIT part
618  */
619 
620 static int __init alsa_mpu401_uart_init(void)
621 {
622 	return 0;
623 }
624 
625 static void __exit alsa_mpu401_uart_exit(void)
626 {
627 }
628 
629 module_init(alsa_mpu401_uart_init)
630 module_exit(alsa_mpu401_uart_exit)
631