xref: /linux/sound/drivers/mpu401/mpu401_uart.c (revision c537b994505099b7197e7d3125b942ecbcc51eb6)
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 /*
270  * input/output open/close - protected by open_mutex in rawmidi.c
271  */
272 static int snd_mpu401_uart_input_open(struct snd_rawmidi_substream *substream)
273 {
274 	struct snd_mpu401 *mpu;
275 	int err;
276 
277 	mpu = substream->rmidi->private_data;
278 	if (mpu->open_input && (err = mpu->open_input(mpu)) < 0)
279 		return err;
280 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode)) {
281 		if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
282 			goto error_out;
283 		if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
284 			goto error_out;
285 	}
286 	mpu->substream_input = substream;
287 	set_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
288 	return 0;
289 
290 error_out:
291 	if (mpu->open_input && mpu->close_input)
292 		mpu->close_input(mpu);
293 	return -EIO;
294 }
295 
296 static int snd_mpu401_uart_output_open(struct snd_rawmidi_substream *substream)
297 {
298 	struct snd_mpu401 *mpu;
299 	int err;
300 
301 	mpu = substream->rmidi->private_data;
302 	if (mpu->open_output && (err = mpu->open_output(mpu)) < 0)
303 		return err;
304 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode)) {
305 		if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
306 			goto error_out;
307 		if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
308 			goto error_out;
309 	}
310 	mpu->substream_output = substream;
311 	set_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
312 	return 0;
313 
314 error_out:
315 	if (mpu->open_output && mpu->close_output)
316 		mpu->close_output(mpu);
317 	return -EIO;
318 }
319 
320 static int snd_mpu401_uart_input_close(struct snd_rawmidi_substream *substream)
321 {
322 	struct snd_mpu401 *mpu;
323 	int err = 0;
324 
325 	mpu = substream->rmidi->private_data;
326 	clear_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
327 	mpu->substream_input = NULL;
328 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode))
329 		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
330 	if (mpu->close_input)
331 		mpu->close_input(mpu);
332 	if (err)
333 		return -EIO;
334 	return 0;
335 }
336 
337 static int snd_mpu401_uart_output_close(struct snd_rawmidi_substream *substream)
338 {
339 	struct snd_mpu401 *mpu;
340 	int err = 0;
341 
342 	mpu = substream->rmidi->private_data;
343 	clear_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
344 	mpu->substream_output = NULL;
345 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode))
346 		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
347 	if (mpu->close_output)
348 		mpu->close_output(mpu);
349 	if (err)
350 		return -EIO;
351 	return 0;
352 }
353 
354 /*
355  * trigger input callback
356  */
357 static void
358 snd_mpu401_uart_input_trigger(struct snd_rawmidi_substream *substream, int up)
359 {
360 	unsigned long flags;
361 	struct snd_mpu401 *mpu;
362 	int max = 64;
363 
364 	mpu = substream->rmidi->private_data;
365 	if (up) {
366 		if (! test_and_set_bit(MPU401_MODE_BIT_INPUT_TRIGGER,
367 				       &mpu->mode)) {
368 			/* first time - flush FIFO */
369 			while (max-- > 0)
370 				mpu->read(mpu, MPU401D(mpu));
371 			if (mpu->irq < 0)
372 				snd_mpu401_uart_add_timer(mpu, 1);
373 		}
374 
375 		/* read data in advance */
376 		spin_lock_irqsave(&mpu->input_lock, flags);
377 		snd_mpu401_uart_input_read(mpu);
378 		spin_unlock_irqrestore(&mpu->input_lock, flags);
379 	} else {
380 		if (mpu->irq < 0)
381 			snd_mpu401_uart_remove_timer(mpu, 1);
382 		clear_bit(MPU401_MODE_BIT_INPUT_TRIGGER, &mpu->mode);
383 	}
384 
385 }
386 
387 /*
388  * transfer input pending data
389  * call with input_lock spinlock held
390  */
391 static void snd_mpu401_uart_input_read(struct snd_mpu401 * mpu)
392 {
393 	int max = 128;
394 	unsigned char byte;
395 
396 	while (max-- > 0) {
397 		if (! snd_mpu401_input_avail(mpu))
398 			break; /* input not available */
399 		byte = mpu->read(mpu, MPU401D(mpu));
400 		if (test_bit(MPU401_MODE_BIT_INPUT_TRIGGER, &mpu->mode))
401 			snd_rawmidi_receive(mpu->substream_input, &byte, 1);
402 	}
403 }
404 
405 /*
406  *  Tx FIFO sizes:
407  *    CS4237B			- 16 bytes
408  *    AudioDrive ES1688         - 12 bytes
409  *    S3 SonicVibes             -  8 bytes
410  *    SoundBlaster AWE 64       -  2 bytes (ugly hardware)
411  */
412 
413 /*
414  * write output pending bytes
415  * call with output_lock spinlock held
416  */
417 static void snd_mpu401_uart_output_write(struct snd_mpu401 * mpu)
418 {
419 	unsigned char byte;
420 	int max = 256, timeout;
421 
422 	do {
423 		if (snd_rawmidi_transmit_peek(mpu->substream_output,
424 					      &byte, 1) == 1) {
425 			for (timeout = 100; timeout > 0; timeout--) {
426 				if (snd_mpu401_output_ready(mpu))
427 					break;
428 			}
429 			if (timeout == 0)
430 				break;	/* Tx FIFO full - try again later */
431 			mpu->write(mpu, byte, MPU401D(mpu));
432 			snd_rawmidi_transmit_ack(mpu->substream_output, 1);
433 		} else {
434 			snd_mpu401_uart_remove_timer (mpu, 0);
435 			break;	/* no other data - leave the tx loop */
436 		}
437 	} while (--max > 0);
438 }
439 
440 /*
441  * output trigger callback
442  */
443 static void
444 snd_mpu401_uart_output_trigger(struct snd_rawmidi_substream *substream, int up)
445 {
446 	unsigned long flags;
447 	struct snd_mpu401 *mpu;
448 
449 	mpu = substream->rmidi->private_data;
450 	if (up) {
451 		set_bit(MPU401_MODE_BIT_OUTPUT_TRIGGER, &mpu->mode);
452 
453 		/* try to add the timer at each output trigger,
454 		 * since the output timer might have been removed in
455 		 * snd_mpu401_uart_output_write().
456 		 */
457 		if (! (mpu->info_flags & MPU401_INFO_TX_IRQ))
458 			snd_mpu401_uart_add_timer(mpu, 0);
459 
460 		/* output pending data */
461 		spin_lock_irqsave(&mpu->output_lock, flags);
462 		snd_mpu401_uart_output_write(mpu);
463 		spin_unlock_irqrestore(&mpu->output_lock, flags);
464 	} else {
465 		if (! (mpu->info_flags & MPU401_INFO_TX_IRQ))
466 			snd_mpu401_uart_remove_timer(mpu, 0);
467 		clear_bit(MPU401_MODE_BIT_OUTPUT_TRIGGER, &mpu->mode);
468 	}
469 }
470 
471 /*
472 
473  */
474 
475 static struct snd_rawmidi_ops snd_mpu401_uart_output =
476 {
477 	.open =		snd_mpu401_uart_output_open,
478 	.close =	snd_mpu401_uart_output_close,
479 	.trigger =	snd_mpu401_uart_output_trigger,
480 };
481 
482 static struct snd_rawmidi_ops snd_mpu401_uart_input =
483 {
484 	.open =		snd_mpu401_uart_input_open,
485 	.close =	snd_mpu401_uart_input_close,
486 	.trigger =	snd_mpu401_uart_input_trigger,
487 };
488 
489 static void snd_mpu401_uart_free(struct snd_rawmidi *rmidi)
490 {
491 	struct snd_mpu401 *mpu = rmidi->private_data;
492 	if (mpu->irq_flags && mpu->irq >= 0)
493 		free_irq(mpu->irq, (void *) mpu);
494 	release_and_free_resource(mpu->res);
495 	kfree(mpu);
496 }
497 
498 /**
499  * snd_mpu401_uart_new - create an MPU401-UART instance
500  * @card: the card instance
501  * @device: the device index, zero-based
502  * @hardware: the hardware type, MPU401_HW_XXXX
503  * @port: the base address of MPU401 port
504  * @info_flags: bitflags MPU401_INFO_XXX
505  * @irq: the irq number, -1 if no interrupt for mpu
506  * @irq_flags: the irq request flags (SA_XXX), 0 if irq was already reserved.
507  * @rrawmidi: the pointer to store the new rawmidi instance
508  *
509  * Creates a new MPU-401 instance.
510  *
511  * Note that the rawmidi instance is returned on the rrawmidi argument,
512  * not the mpu401 instance itself.  To access to the mpu401 instance,
513  * cast from rawmidi->private_data (with struct snd_mpu401 magic-cast).
514  *
515  * Returns zero if successful, or a negative error code.
516  */
517 int snd_mpu401_uart_new(struct snd_card *card, int device,
518 			unsigned short hardware,
519 			unsigned long port,
520 			unsigned int info_flags,
521 			int irq, int irq_flags,
522 			struct snd_rawmidi ** rrawmidi)
523 {
524 	struct snd_mpu401 *mpu;
525 	struct snd_rawmidi *rmidi;
526 	int in_enable, out_enable;
527 	int err;
528 
529 	if (rrawmidi)
530 		*rrawmidi = NULL;
531 	if (! (info_flags & (MPU401_INFO_INPUT | MPU401_INFO_OUTPUT)))
532 		info_flags |= MPU401_INFO_INPUT | MPU401_INFO_OUTPUT;
533 	in_enable = (info_flags & MPU401_INFO_INPUT) ? 1 : 0;
534 	out_enable = (info_flags & MPU401_INFO_OUTPUT) ? 1 : 0;
535 	if ((err = snd_rawmidi_new(card, "MPU-401U", device,
536 				   out_enable, in_enable, &rmidi)) < 0)
537 		return err;
538 	mpu = kzalloc(sizeof(*mpu), GFP_KERNEL);
539 	if (mpu == NULL) {
540 		snd_printk(KERN_ERR "mpu401_uart: cannot allocate\n");
541 		snd_device_free(card, rmidi);
542 		return -ENOMEM;
543 	}
544 	rmidi->private_data = mpu;
545 	rmidi->private_free = snd_mpu401_uart_free;
546 	spin_lock_init(&mpu->input_lock);
547 	spin_lock_init(&mpu->output_lock);
548 	spin_lock_init(&mpu->timer_lock);
549 	mpu->hardware = hardware;
550 	if (! (info_flags & MPU401_INFO_INTEGRATED)) {
551 		int res_size = hardware == MPU401_HW_PC98II ? 4 : 2;
552 		mpu->res = request_region(port, res_size, "MPU401 UART");
553 		if (mpu->res == NULL) {
554 			snd_printk(KERN_ERR "mpu401_uart: "
555 				   "unable to grab port 0x%lx size %d\n",
556 				   port, res_size);
557 			snd_device_free(card, rmidi);
558 			return -EBUSY;
559 		}
560 	}
561 	if (info_flags & MPU401_INFO_MMIO) {
562 		mpu->write = mpu401_write_mmio;
563 		mpu->read = mpu401_read_mmio;
564 	} else {
565 		mpu->write = mpu401_write_port;
566 		mpu->read = mpu401_read_port;
567 	}
568 	mpu->port = port;
569 	if (hardware == MPU401_HW_PC98II)
570 		mpu->cport = port + 2;
571 	else
572 		mpu->cport = port + 1;
573 	if (irq >= 0 && irq_flags) {
574 		if (request_irq(irq, snd_mpu401_uart_interrupt, irq_flags,
575 				"MPU401 UART", (void *) mpu)) {
576 			snd_printk(KERN_ERR "mpu401_uart: "
577 				   "unable to grab IRQ %d\n", irq);
578 			snd_device_free(card, rmidi);
579 			return -EBUSY;
580 		}
581 	}
582 	mpu->info_flags = info_flags;
583 	mpu->irq = irq;
584 	mpu->irq_flags = irq_flags;
585 	if (card->shortname[0])
586 		snprintf(rmidi->name, sizeof(rmidi->name), "%s MIDI",
587 			 card->shortname);
588 	else
589 		sprintf(rmidi->name, "MPU-401 MIDI %d-%d",card->number, device);
590 	if (out_enable) {
591 		snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
592 				    &snd_mpu401_uart_output);
593 		rmidi->info_flags |= SNDRV_RAWMIDI_INFO_OUTPUT;
594 	}
595 	if (in_enable) {
596 		snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT,
597 				    &snd_mpu401_uart_input);
598 		rmidi->info_flags |= SNDRV_RAWMIDI_INFO_INPUT;
599 		if (out_enable)
600 			rmidi->info_flags |= SNDRV_RAWMIDI_INFO_DUPLEX;
601 	}
602 	mpu->rmidi = rmidi;
603 	if (rrawmidi)
604 		*rrawmidi = rmidi;
605 	return 0;
606 }
607 
608 EXPORT_SYMBOL(snd_mpu401_uart_new);
609 
610 /*
611  *  INIT part
612  */
613 
614 static int __init alsa_mpu401_uart_init(void)
615 {
616 	return 0;
617 }
618 
619 static void __exit alsa_mpu401_uart_exit(void)
620 {
621 }
622 
623 module_init(alsa_mpu401_uart_init)
624 module_exit(alsa_mpu401_uart_exit)
625