linux/sound/sound_core.c
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   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, "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(&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(&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(&sound_loader_lock);
 248retry:
 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
 284fail:
 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        
 295static 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
 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(_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 
 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(&chains[0], fops, dev, 0, 128,
 436                                 "mixer", 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(&chains[3], fops, dev, 3, 131,
 464                                 "dsp", 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(&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(&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(&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(&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
 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, "sound");
 604}
 605
 606static 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 */
 618