sound/sound_core.c

   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
  22 static inline int init_oss_soundcore(void)      { return 0; }
  23 static inline void cleanup_oss_soundcore(void)  { }
  24 #endif
  25
  26 MODULE_DESCRIPTION("Core sound module");
  27 MODULE_AUTHOR("Alan Cox");
  28 MODULE_LICENSE("GPL");
  29
  30 static 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, "snd/%s", dev_name(dev));
  35 }
  36
  37 const struct class sound_class = {
  38         .name = "sound",
  39         .devnode = sound_devnode,
  40 };
  41 EXPORT_SYMBOL(sound_class);
  42
  43 static 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(&sound_class);
  52         if (rc) {
  53                 cleanup_oss_soundcore();
  54                 return rc;
  55         }
  56
  57         return 0;
  58 }
  59
  60 static void __exit cleanup_soundcore(void)
  61 {
  62         cleanup_oss_soundcore();
  63         class_unregister(&sound_class);
  64 }
  65
  66 subsys_initcall(init_soundcore);
  67 module_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
 110 struct 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  */
 140 static int preclaim_oss = IS_ENABLED(CONFIG_SOUND_OSS_CORE_PRECLAIM);
 141
 142 module_param(preclaim_oss, int, 0444);
 143
 144 static int soundcore_open(struct inode *, struct file *);
 145
 146 static 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
 159 static 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
 212 static 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
 232 static 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
 239 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)
 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(&sound_loader_lock);
 248 retry:
 249         r = __sound_insert_unit(s, list, fops, index, low, top);
 250         spin_unlock(&sound_loader_lock);
 251
 252         if (r < 0)
 253                 goto fail;
 254         else if (r < SOUND_STEP)
 255                 sprintf(s->name, "sound/%s", name);
 256         else
 257                 sprintf(s->name, "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, s->unit_minor, 1, s->name,
 266                                       &soundcore_fops);
 267                 if (r < 0) {
 268                         spin_lock(&sound_loader_lock);
 269                         __sound_remove_unit(list, s->unit_minor);
 270                         if (index < 0) {
 271                                 low = s->unit_minor + SOUND_STEP;
 272                                 goto retry;
 273                         }
 274                         spin_unlock(&sound_loader_lock);
 275                         r = -EBUSY;
 276                         goto fail;
 277                 }
 278         }
 279
 280         device_create(&sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
 281                       NULL, "%s", s->name+6);
 282         return s->unit_minor;
 283
 284 fail:
 285         kfree(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
 295 static void sound_remove_unit(struct sound_unit **list, int unit)
 296 {
 297         struct sound_unit *p;
 298
 299         spin_lock(&sound_loader_lock);
 300         p = __sound_remove_unit(list, unit);
 301         spin_unlock(&sound_loader_lock);
 302         if (p) {
 303                 if (!preclaim_oss)
 304                         __unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
 305                                             p->name);
 306                 device_destroy(&sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
 307                 kfree(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
 332 static 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
 347 int 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(_name, "unknown%d", chain);
 402                         if (unit >= SOUND_STEP)
 403                                 strcat(_name, "-");
 404                         name = _name;
 405                 }
 406                 break;
 407         }
 408         return sound_insert_unit(&chains[chain], fops, -1, unit, max_unit,
 409                                  name, 0600, dev);
 410 }
 411
 412 EXPORT_SYMBOL(register_sound_special_device);
 413
 414 int register_sound_special(const struct file_operations *fops, int unit)
 415 {
 416         return register_sound_special_device(fops, unit, NULL);
 417 }
 418
 419 EXPORT_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
 433 int register_sound_mixer(const struct file_operations *fops, int dev)
 434 {
 435         return sound_insert_unit(&chains[0], fops, dev, 0, 128,
 436                                  "mixer", 0600, NULL);
 437 }
 438
 439 EXPORT_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
 461 int register_sound_dsp(const struct file_operations *fops, int dev)
 462 {
 463         return sound_insert_unit(&chains[3], fops, dev, 3, 131,
 464                                  "dsp", 0600, NULL);
 465 }
 466
 467 EXPORT_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
 479 void unregister_sound_special(int unit)
 480 {
 481         sound_remove_unit(&chains[unit % SOUND_STEP], unit);
 482 }
 483
 484 EXPORT_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
 494 void unregister_sound_mixer(int unit)
 495 {
 496         sound_remove_unit(&chains[0], unit);
 497 }
 498
 499 EXPORT_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
 511 void unregister_sound_dsp(int unit)
 512 {
 513         sound_remove_unit(&chains[3], unit);
 514 }
 515
 516
 517 EXPORT_SYMBOL(unregister_sound_dsp);
 518
 519 static 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
 533 static 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(&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(&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(&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(&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
 597 MODULE_ALIAS_CHARDEV_MAJOR(SOUND_MAJOR);
 598
 599 static 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, "sound");
 604 }
 605
 606 static int __init init_oss_soundcore(void)
 607 {
 608         if (preclaim_oss &&
 609             register_chrdev(SOUND_MAJOR, "sound", &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 */