1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	Sound core.  This file is composed of two parts.  sound_class
4  *	which is common to both OSS and ALSA and OSS sound core which
5  *	is used OSS or emulation of it.
6  */
7 
8 /*
9  * First, the common part.
10  */
11 #include <linux/module.h>
12 #include <linux/device.h>
13 #include <linux/err.h>
14 #include <linux/kdev_t.h>
15 #include <linux/major.h>
16 #include <sound/core.h>
17 
18 #ifdef CONFIG_SOUND_OSS_CORE
19 static int __init init_oss_soundcore(void);
20 static void cleanup_oss_soundcore(void);
21 #else
init_oss_soundcore(void)22 static inline int init_oss_soundcore(void)	{ return 0; }
cleanup_oss_soundcore(void)23 static inline void cleanup_oss_soundcore(void)	{ }
24 #endif
25 
26 struct class *sound_class;
27 EXPORT_SYMBOL(sound_class);
28 
29 MODULE_DESCRIPTION("Core sound module");
30 MODULE_AUTHOR("Alan Cox");
31 MODULE_LICENSE("GPL");
32 
sound_devnode(struct device * dev,umode_t * mode)33 static char *sound_devnode(struct device *dev, umode_t *mode)
34 {
35 	if (MAJOR(dev->devt) == SOUND_MAJOR)
36 		return NULL;
37 	return kasprintf(GFP_KERNEL, "snd/%s", dev_name(dev));
38 }
39 
init_soundcore(void)40 static int __init init_soundcore(void)
41 {
42 	int rc;
43 
44 	rc = init_oss_soundcore();
45 	if (rc)
46 		return rc;
47 
48 	sound_class = class_create(THIS_MODULE, "sound");
49 	if (IS_ERR(sound_class)) {
50 		cleanup_oss_soundcore();
51 		return PTR_ERR(sound_class);
52 	}
53 
54 	sound_class->devnode = sound_devnode;
55 
56 	return 0;
57 }
58 
cleanup_soundcore(void)59 static void __exit cleanup_soundcore(void)
60 {
61 	cleanup_oss_soundcore();
62 	class_destroy(sound_class);
63 }
64 
65 subsys_initcall(init_soundcore);
66 module_exit(cleanup_soundcore);
67 
68 
69 #ifdef CONFIG_SOUND_OSS_CORE
70 /*
71  *	OSS sound core handling. Breaks out sound functions to submodules
72  *
73  *	Author:		Alan Cox <alan@lxorguk.ukuu.org.uk>
74  *
75  *	Fixes:
76  *
77  *                         --------------------
78  *
79  *	Top level handler for the sound subsystem. Various devices can
80  *	plug into this. The fact they don't all go via OSS doesn't mean
81  *	they don't have to implement the OSS API. There is a lot of logic
82  *	to keeping much of the OSS weight out of the code in a compatibility
83  *	module, but it's up to the driver to rember to load it...
84  *
85  *	The code provides a set of functions for registration of devices
86  *	by type. This is done rather than providing a single call so that
87  *	we can hide any future changes in the internals (eg when we go to
88  *	32bit dev_t) from the modules and their interface.
89  *
90  *	Secondly we need to allocate the dsp, dsp16 and audio devices as
91  *	one. Thus we misuse the chains a bit to simplify this.
92  *
93  *	Thirdly to make it more fun and for 2.3.x and above we do all
94  *	of this using fine grained locking.
95  *
96  *	FIXME: we have to resolve modules and fine grained load/unload
97  *	locking at some point in 2.3.x.
98  */
99 
100 #include <linux/init.h>
101 #include <linux/slab.h>
102 #include <linux/types.h>
103 #include <linux/kernel.h>
104 #include <linux/sound.h>
105 #include <linux/kmod.h>
106 
107 #define SOUND_STEP 16
108 
109 struct sound_unit
110 {
111 	int unit_minor;
112 	const struct file_operations *unit_fops;
113 	struct sound_unit *next;
114 	char name[32];
115 };
116 
117 /*
118  * By default, OSS sound_core claims full legacy minor range (0-255)
119  * of SOUND_MAJOR to trap open attempts to any sound minor and
120  * requests modules using custom sound-slot/service-* module aliases.
121  * The only benefit of doing this is allowing use of custom module
122  * aliases instead of the standard char-major-* ones.  This behavior
123  * prevents alternative OSS implementation and is scheduled to be
124  * removed.
125  *
126  * CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss kernel
127  * parameter are added to allow distros and developers to try and
128  * switch to alternative implementations without needing to rebuild
129  * the kernel in the meantime.  If preclaim_oss is non-zero, the
130  * kernel will behave the same as before.  All SOUND_MAJOR minors are
131  * preclaimed and the custom module aliases along with standard chrdev
132  * ones are emitted if a missing device is opened.  If preclaim_oss is
133  * zero, sound_core only grabs what's actually in use and for missing
134  * devices only the standard chrdev aliases are requested.
135  *
136  * All these clutters are scheduled to be removed along with
137  * sound-slot/service-* module aliases.
138  */
139 #ifdef CONFIG_SOUND_OSS_CORE_PRECLAIM
140 static int preclaim_oss = 1;
141 #else
142 static int preclaim_oss = 0;
143 #endif
144 
145 module_param(preclaim_oss, int, 0444);
146 
147 static int soundcore_open(struct inode *, struct file *);
148 
149 static const struct file_operations soundcore_fops =
150 {
151 	/* We must have an owner or the module locking fails */
152 	.owner	= THIS_MODULE,
153 	.open	= soundcore_open,
154 	.llseek = noop_llseek,
155 };
156 
157 /*
158  *	Low level list operator. Scan the ordered list, find a hole and
159  *	join into it. Called with the lock asserted
160  */
161 
__sound_insert_unit(struct sound_unit * s,struct sound_unit ** list,const struct file_operations * fops,int index,int low,int top)162 static int __sound_insert_unit(struct sound_unit * s, struct sound_unit **list, const struct file_operations *fops, int index, int low, int top)
163 {
164 	int n=low;
165 
166 	if (index < 0) {	/* first free */
167 
168 		while (*list && (*list)->unit_minor<n)
169 			list=&((*list)->next);
170 
171 		while(n<top)
172 		{
173 			/* Found a hole ? */
174 			if(*list==NULL || (*list)->unit_minor>n)
175 				break;
176 			list=&((*list)->next);
177 			n+=SOUND_STEP;
178 		}
179 
180 		if(n>=top)
181 			return -ENOENT;
182 	} else {
183 		n = low+(index*16);
184 		while (*list) {
185 			if ((*list)->unit_minor==n)
186 				return -EBUSY;
187 			if ((*list)->unit_minor>n)
188 				break;
189 			list=&((*list)->next);
190 		}
191 	}
192 
193 	/*
194 	 *	Fill it in
195 	 */
196 
197 	s->unit_minor=n;
198 	s->unit_fops=fops;
199 
200 	/*
201 	 *	Link it
202 	 */
203 
204 	s->next=*list;
205 	*list=s;
206 
207 
208 	return n;
209 }
210 
211 /*
212  *	Remove a node from the chain. Called with the lock asserted
213  */
214 
__sound_remove_unit(struct sound_unit ** list,int unit)215 static struct sound_unit *__sound_remove_unit(struct sound_unit **list, int unit)
216 {
217 	while(*list)
218 	{
219 		struct sound_unit *p=*list;
220 		if(p->unit_minor==unit)
221 		{
222 			*list=p->next;
223 			return p;
224 		}
225 		list=&(p->next);
226 	}
227 	printk(KERN_ERR "Sound device %d went missing!\n", unit);
228 	return NULL;
229 }
230 
231 /*
232  *	This lock guards the sound loader list.
233  */
234 
235 static DEFINE_SPINLOCK(sound_loader_lock);
236 
237 /*
238  *	Allocate the controlling structure and add it to the sound driver
239  *	list. Acquires locks as needed
240  */
241 
sound_insert_unit(struct sound_unit ** list,const struct file_operations * fops,int index,int low,int top,const char * name,umode_t mode,struct device * dev)242 static int sound_insert_unit(struct sound_unit **list, const struct file_operations *fops, int index, int low, int top, const char *name, umode_t mode, struct device *dev)
243 {
244 	struct sound_unit *s = kmalloc(sizeof(*s), GFP_KERNEL);
245 	int r;
246 
247 	if (!s)
248 		return -ENOMEM;
249 
250 	spin_lock(&sound_loader_lock);
251 retry:
252 	r = __sound_insert_unit(s, list, fops, index, low, top);
253 	spin_unlock(&sound_loader_lock);
254 
255 	if (r < 0)
256 		goto fail;
257 	else if (r < SOUND_STEP)
258 		sprintf(s->name, "sound/%s", name);
259 	else
260 		sprintf(s->name, "sound/%s%d", name, r / SOUND_STEP);
261 
262 	if (!preclaim_oss) {
263 		/*
264 		 * Something else might have grabbed the minor.  If
265 		 * first free slot is requested, rescan with @low set
266 		 * to the next unit; otherwise, -EBUSY.
267 		 */
268 		r = __register_chrdev(SOUND_MAJOR, s->unit_minor, 1, s->name,
269 				      &soundcore_fops);
270 		if (r < 0) {
271 			spin_lock(&sound_loader_lock);
272 			__sound_remove_unit(list, s->unit_minor);
273 			if (index < 0) {
274 				low = s->unit_minor + SOUND_STEP;
275 				goto retry;
276 			}
277 			spin_unlock(&sound_loader_lock);
278 			r = -EBUSY;
279 			goto fail;
280 		}
281 	}
282 
283 	device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
284 		      NULL, "%s", s->name+6);
285 	return s->unit_minor;
286 
287 fail:
288 	kfree(s);
289 	return r;
290 }
291 
292 /*
293  *	Remove a unit. Acquires locks as needed. The drivers MUST have
294  *	completed the removal before their file operations become
295  *	invalid.
296  */
297 
sound_remove_unit(struct sound_unit ** list,int unit)298 static void sound_remove_unit(struct sound_unit **list, int unit)
299 {
300 	struct sound_unit *p;
301 
302 	spin_lock(&sound_loader_lock);
303 	p = __sound_remove_unit(list, unit);
304 	spin_unlock(&sound_loader_lock);
305 	if (p) {
306 		if (!preclaim_oss)
307 			__unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
308 					    p->name);
309 		device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
310 		kfree(p);
311 	}
312 }
313 
314 /*
315  *	Allocations
316  *
317  *	0	*16		Mixers
318  *	1	*8		Sequencers
319  *	2	*16		Midi
320  *	3	*16		DSP
321  *	4	*16		SunDSP
322  *	5	*16		DSP16
323  *	6	--		sndstat (obsolete)
324  *	7	*16		unused
325  *	8	--		alternate sequencer (see above)
326  *	9	*16		raw synthesizer access
327  *	10	*16		unused
328  *	11	*16		unused
329  *	12	*16		unused
330  *	13	*16		unused
331  *	14	*16		unused
332  *	15	*16		unused
333  */
334 
335 static struct sound_unit *chains[SOUND_STEP];
336 
337 /**
338  *	register_sound_special_device - register a special sound node
339  *	@fops: File operations for the driver
340  *	@unit: Unit number to allocate
341  *      @dev: device pointer
342  *
343  *	Allocate a special sound device by minor number from the sound
344  *	subsystem.
345  *
346  *	Return: The allocated number is returned on success. On failure,
347  *	a negative error code is returned.
348  */
349 
register_sound_special_device(const struct file_operations * fops,int unit,struct device * dev)350 int register_sound_special_device(const struct file_operations *fops, int unit,
351 				  struct device *dev)
352 {
353 	const int chain = unit % SOUND_STEP;
354 	int max_unit = 256;
355 	const char *name;
356 	char _name[16];
357 
358 	switch (chain) {
359 	    case 0:
360 		name = "mixer";
361 		break;
362 	    case 1:
363 		name = "sequencer";
364 		if (unit >= SOUND_STEP)
365 			goto __unknown;
366 		max_unit = unit + 1;
367 		break;
368 	    case 2:
369 		name = "midi";
370 		break;
371 	    case 3:
372 		name = "dsp";
373 		break;
374 	    case 4:
375 		name = "audio";
376 		break;
377 	    case 5:
378 		name = "dspW";
379 		break;
380 	    case 8:
381 		name = "sequencer2";
382 		if (unit >= SOUND_STEP)
383 			goto __unknown;
384 		max_unit = unit + 1;
385 		break;
386 	    case 9:
387 		name = "dmmidi";
388 		break;
389 	    case 10:
390 		name = "dmfm";
391 		break;
392 	    case 12:
393 		name = "adsp";
394 		break;
395 	    case 13:
396 		name = "amidi";
397 		break;
398 	    case 14:
399 		name = "admmidi";
400 		break;
401 	    default:
402 	    	{
403 		    __unknown:
404 			sprintf(_name, "unknown%d", chain);
405 		    	if (unit >= SOUND_STEP)
406 		    		strcat(_name, "-");
407 		    	name = _name;
408 		}
409 		break;
410 	}
411 	return sound_insert_unit(&chains[chain], fops, -1, unit, max_unit,
412 				 name, 0600, dev);
413 }
414 
415 EXPORT_SYMBOL(register_sound_special_device);
416 
register_sound_special(const struct file_operations * fops,int unit)417 int register_sound_special(const struct file_operations *fops, int unit)
418 {
419 	return register_sound_special_device(fops, unit, NULL);
420 }
421 
422 EXPORT_SYMBOL(register_sound_special);
423 
424 /**
425  *	register_sound_mixer - register a mixer device
426  *	@fops: File operations for the driver
427  *	@dev: Unit number to allocate
428  *
429  *	Allocate a mixer device. Unit is the number of the mixer requested.
430  *	Pass -1 to request the next free mixer unit.
431  *
432  *	Return: On success, the allocated number is returned. On failure,
433  *	a negative error code is returned.
434  */
435 
register_sound_mixer(const struct file_operations * fops,int dev)436 int register_sound_mixer(const struct file_operations *fops, int dev)
437 {
438 	return sound_insert_unit(&chains[0], fops, dev, 0, 128,
439 				 "mixer", 0600, NULL);
440 }
441 
442 EXPORT_SYMBOL(register_sound_mixer);
443 
444 /*
445  *	DSP's are registered as a triple. Register only one and cheat
446  *	in open - see below.
447  */
448 
449 /**
450  *	register_sound_dsp - register a DSP device
451  *	@fops: File operations for the driver
452  *	@dev: Unit number to allocate
453  *
454  *	Allocate a DSP device. Unit is the number of the DSP requested.
455  *	Pass -1 to request the next free DSP unit.
456  *
457  *	This function allocates both the audio and dsp device entries together
458  *	and will always allocate them as a matching pair - eg dsp3/audio3
459  *
460  *	Return: On success, the allocated number is returned. On failure,
461  *	a negative error code is returned.
462  */
463 
register_sound_dsp(const struct file_operations * fops,int dev)464 int register_sound_dsp(const struct file_operations *fops, int dev)
465 {
466 	return sound_insert_unit(&chains[3], fops, dev, 3, 131,
467 				 "dsp", 0600, NULL);
468 }
469 
470 EXPORT_SYMBOL(register_sound_dsp);
471 
472 /**
473  *	unregister_sound_special - unregister a special sound device
474  *	@unit: unit number to allocate
475  *
476  *	Release a sound device that was allocated with
477  *	register_sound_special(). The unit passed is the return value from
478  *	the register function.
479  */
480 
481 
unregister_sound_special(int unit)482 void unregister_sound_special(int unit)
483 {
484 	sound_remove_unit(&chains[unit % SOUND_STEP], unit);
485 }
486 
487 EXPORT_SYMBOL(unregister_sound_special);
488 
489 /**
490  *	unregister_sound_mixer - unregister a mixer
491  *	@unit: unit number to allocate
492  *
493  *	Release a sound device that was allocated with register_sound_mixer().
494  *	The unit passed is the return value from the register function.
495  */
496 
unregister_sound_mixer(int unit)497 void unregister_sound_mixer(int unit)
498 {
499 	sound_remove_unit(&chains[0], unit);
500 }
501 
502 EXPORT_SYMBOL(unregister_sound_mixer);
503 
504 /**
505  *	unregister_sound_dsp - unregister a DSP device
506  *	@unit: unit number to allocate
507  *
508  *	Release a sound device that was allocated with register_sound_dsp().
509  *	The unit passed is the return value from the register function.
510  *
511  *	Both of the allocated units are released together automatically.
512  */
513 
unregister_sound_dsp(int unit)514 void unregister_sound_dsp(int unit)
515 {
516 	sound_remove_unit(&chains[3], unit);
517 }
518 
519 
520 EXPORT_SYMBOL(unregister_sound_dsp);
521 
__look_for_unit(int chain,int unit)522 static struct sound_unit *__look_for_unit(int chain, int unit)
523 {
524 	struct sound_unit *s;
525 
526 	s=chains[chain];
527 	while(s && s->unit_minor <= unit)
528 	{
529 		if(s->unit_minor==unit)
530 			return s;
531 		s=s->next;
532 	}
533 	return NULL;
534 }
535 
soundcore_open(struct inode * inode,struct file * file)536 static int soundcore_open(struct inode *inode, struct file *file)
537 {
538 	int chain;
539 	int unit = iminor(inode);
540 	struct sound_unit *s;
541 	const struct file_operations *new_fops = NULL;
542 
543 	chain=unit&0x0F;
544 	if(chain==4 || chain==5)	/* dsp/audio/dsp16 */
545 	{
546 		unit&=0xF0;
547 		unit|=3;
548 		chain=3;
549 	}
550 
551 	spin_lock(&sound_loader_lock);
552 	s = __look_for_unit(chain, unit);
553 	if (s)
554 		new_fops = fops_get(s->unit_fops);
555 	if (preclaim_oss && !new_fops) {
556 		spin_unlock(&sound_loader_lock);
557 
558 		/*
559 		 *  Please, don't change this order or code.
560 		 *  For ALSA slot means soundcard and OSS emulation code
561 		 *  comes as add-on modules which aren't depend on
562 		 *  ALSA toplevel modules for soundcards, thus we need
563 		 *  load them at first.	  [Jaroslav Kysela <perex@jcu.cz>]
564 		 */
565 		request_module("sound-slot-%i", unit>>4);
566 		request_module("sound-service-%i-%i", unit>>4, chain);
567 
568 		/*
569 		 * sound-slot/service-* module aliases are scheduled
570 		 * for removal in favor of the standard char-major-*
571 		 * module aliases.  For the time being, generate both
572 		 * the legacy and standard module aliases to ease
573 		 * transition.
574 		 */
575 		if (request_module("char-major-%d-%d", SOUND_MAJOR, unit) > 0)
576 			request_module("char-major-%d", SOUND_MAJOR);
577 
578 		spin_lock(&sound_loader_lock);
579 		s = __look_for_unit(chain, unit);
580 		if (s)
581 			new_fops = fops_get(s->unit_fops);
582 	}
583 	spin_unlock(&sound_loader_lock);
584 	if (new_fops) {
585 		/*
586 		 * We rely upon the fact that we can't be unloaded while the
587 		 * subdriver is there.
588 		 */
589 		int err = 0;
590 		replace_fops(file, new_fops);
591 
592 		if (file->f_op->open)
593 			err = file->f_op->open(inode,file);
594 
595 		return err;
596 	}
597 	return -ENODEV;
598 }
599 
600 MODULE_ALIAS_CHARDEV_MAJOR(SOUND_MAJOR);
601 
cleanup_oss_soundcore(void)602 static void cleanup_oss_soundcore(void)
603 {
604 	/* We have nothing to really do here - we know the lists must be
605 	   empty */
606 	unregister_chrdev(SOUND_MAJOR, "sound");
607 }
608 
init_oss_soundcore(void)609 static int __init init_oss_soundcore(void)
610 {
611 	if (preclaim_oss &&
612 	    register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops) < 0) {
613 		printk(KERN_ERR "soundcore: sound device already in use.\n");
614 		return -EBUSY;
615 	}
616 
617 	return 0;
618 }
619 
620 #endif /* CONFIG_SOUND_OSS_CORE */
621