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

source code of linux/sound/sound_core.c