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sound_core.c

/*
 *    Sound core.  This file is composed of two parts.  sound_class
 *    which is common to both OSS and ALSA and OSS sound core which
 *    is used OSS or emulation of it.
 */

/*
 * First, the common part.
 */
#include <linux/module.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/kdev_t.h>
#include <linux/major.h>
#include <sound/core.h>

#ifdef CONFIG_SOUND_OSS_CORE
static int __init init_oss_soundcore(void);
static void cleanup_oss_soundcore(void);
#else
static inline int init_oss_soundcore(void)      { return 0; }
static inline void cleanup_oss_soundcore(void)  { }
#endif

struct class *sound_class;
EXPORT_SYMBOL(sound_class);

MODULE_DESCRIPTION("Core sound module");
MODULE_AUTHOR("Alan Cox");
MODULE_LICENSE("GPL");

static char *sound_devnode(struct device *dev, mode_t *mode)
{
      if (MAJOR(dev->devt) == SOUND_MAJOR)
            return NULL;
      return kasprintf(GFP_KERNEL, "snd/%s", dev_name(dev));
}

static int __init init_soundcore(void)
{
      int rc;

      rc = init_oss_soundcore();
      if (rc)
            return rc;

      sound_class = class_create(THIS_MODULE, "sound");
      if (IS_ERR(sound_class)) {
            cleanup_oss_soundcore();
            return PTR_ERR(sound_class);
      }

      sound_class->devnode = sound_devnode;

      return 0;
}

static void __exit cleanup_soundcore(void)
{
      cleanup_oss_soundcore();
      class_destroy(sound_class);
}

subsys_initcall(init_soundcore);
module_exit(cleanup_soundcore);


#ifdef CONFIG_SOUND_OSS_CORE
/*
 *    OSS sound core handling. Breaks out sound functions to submodules
 *    
 *    Author:           Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *    Fixes:
 *
 *
 *    This program is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU General Public License
 *    as published by the Free Software Foundation; either version
 *    2 of the License, or (at your option) any later version.
 *
 *                         --------------------
 * 
 *    Top level handler for the sound subsystem. Various devices can
 *    plug into this. The fact they don't all go via OSS doesn't mean 
 *    they don't have to implement the OSS API. There is a lot of logic
 *    to keeping much of the OSS weight out of the code in a compatibility
 *    module, but it's up to the driver to rember to load it...
 *
 *    The code provides a set of functions for registration of devices
 *    by type. This is done rather than providing a single call so that
 *    we can hide any future changes in the internals (eg when we go to
 *    32bit dev_t) from the modules and their interface.
 *
 *    Secondly we need to allocate the dsp, dsp16 and audio devices as
 *    one. Thus we misuse the chains a bit to simplify this.
 *
 *    Thirdly to make it more fun and for 2.3.x and above we do all
 *    of this using fine grained locking.
 *
 *    FIXME: we have to resolve modules and fine grained load/unload
 *    locking at some point in 2.3.x.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sound.h>
#include <linux/kmod.h>

#define SOUND_STEP 16

struct sound_unit
{
      int unit_minor;
      const struct file_operations *unit_fops;
      struct sound_unit *next;
      char name[32];
};

#ifdef CONFIG_SOUND_MSNDCLAS
extern int msnd_classic_init(void);
#endif
#ifdef CONFIG_SOUND_MSNDPIN
extern int msnd_pinnacle_init(void);
#endif

/*
 * By default, OSS sound_core claims full legacy minor range (0-255)
 * of SOUND_MAJOR to trap open attempts to any sound minor and
 * requests modules using custom sound-slot/service-* module aliases.
 * The only benefit of doing this is allowing use of custom module
 * aliases instead of the standard char-major-* ones.  This behavior
 * prevents alternative OSS implementation and is scheduled to be
 * removed.
 *
 * CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss kernel
 * parameter are added to allow distros and developers to try and
 * switch to alternative implementations without needing to rebuild
 * the kernel in the meantime.  If preclaim_oss is non-zero, the
 * kernel will behave the same as before.  All SOUND_MAJOR minors are
 * preclaimed and the custom module aliases along with standard chrdev
 * ones are emitted if a missing device is opened.  If preclaim_oss is
 * zero, sound_core only grabs what's actually in use and for missing
 * devices only the standard chrdev aliases are requested.
 *
 * All these clutters are scheduled to be removed along with
 * sound-slot/service-* module aliases.  Please take a look at
 * feature-removal-schedule.txt for details.
 */
#ifdef CONFIG_SOUND_OSS_CORE_PRECLAIM
static int preclaim_oss = 1;
#else
static int preclaim_oss = 0;
#endif

module_param(preclaim_oss, int, 0444);

static int soundcore_open(struct inode *, struct file *);

static const struct file_operations soundcore_fops =
{
      /* We must have an owner or the module locking fails */
      .owner      = THIS_MODULE,
      .open = soundcore_open,
      .llseek = noop_llseek,
};

/*
 *    Low level list operator. Scan the ordered list, find a hole and
 *    join into it. Called with the lock asserted
 */

static int __sound_insert_unit(struct sound_unit * s, struct sound_unit **list, const struct file_operations *fops, int index, int low, int top)
{
      int n=low;

      if (index < 0) {  /* first free */

            while (*list && (*list)->unit_minor<n)
                  list=&((*list)->next);

            while(n<top)
            {
                  /* Found a hole ? */
                  if(*list==NULL || (*list)->unit_minor>n)
                        break;
                  list=&((*list)->next);
                  n+=SOUND_STEP;
            }

            if(n>=top)
                  return -ENOENT;
      } else {
            n = low+(index*16);
            while (*list) {
                  if ((*list)->unit_minor==n)
                        return -EBUSY;
                  if ((*list)->unit_minor>n)
                        break;
                  list=&((*list)->next);
            }
      }     
            
      /*
       *    Fill it in
       */
       
      s->unit_minor=n;
      s->unit_fops=fops;
      
      /*
       *    Link it
       */
       
      s->next=*list;
      *list=s;
      
      
      return n;
}

/*
 *    Remove a node from the chain. Called with the lock asserted
 */
 
static struct sound_unit *__sound_remove_unit(struct sound_unit **list, int unit)
{
      while(*list)
      {
            struct sound_unit *p=*list;
            if(p->unit_minor==unit)
            {
                  *list=p->next;
                  return p;
            }
            list=&(p->next);
      }
      printk(KERN_ERR "Sound device %d went missing!\n", unit);
      return NULL;
}

/*
 *    This lock guards the sound loader list.
 */

static DEFINE_SPINLOCK(sound_loader_lock);

/*
 *    Allocate the controlling structure and add it to the sound driver
 *    list. Acquires locks as needed
 */

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)
{
      struct sound_unit *s = kmalloc(sizeof(*s), GFP_KERNEL);
      int r;

      if (!s)
            return -ENOMEM;

      spin_lock(&sound_loader_lock);
retry:
      r = __sound_insert_unit(s, list, fops, index, low, top);
      spin_unlock(&sound_loader_lock);
      
      if (r < 0)
            goto fail;
      else if (r < SOUND_STEP)
            sprintf(s->name, "sound/%s", name);
      else
            sprintf(s->name, "sound/%s%d", name, r / SOUND_STEP);

      if (!preclaim_oss) {
            /*
             * Something else might have grabbed the minor.  If
             * first free slot is requested, rescan with @low set
             * to the next unit; otherwise, -EBUSY.
             */
            r = __register_chrdev(SOUND_MAJOR, s->unit_minor, 1, s->name,
                              &soundcore_fops);
            if (r < 0) {
                  spin_lock(&sound_loader_lock);
                  __sound_remove_unit(list, s->unit_minor);
                  if (index < 0) {
                        low = s->unit_minor + SOUND_STEP;
                        goto retry;
                  }
                  spin_unlock(&sound_loader_lock);
                  return -EBUSY;
            }
      }

      device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
                  NULL, s->name+6);
      return s->unit_minor;

fail:
      kfree(s);
      return r;
}

/*
 *    Remove a unit. Acquires locks as needed. The drivers MUST have
 *    completed the removal before their file operations become
 *    invalid.
 */
      
static void sound_remove_unit(struct sound_unit **list, int unit)
{
      struct sound_unit *p;

      spin_lock(&sound_loader_lock);
      p = __sound_remove_unit(list, unit);
      spin_unlock(&sound_loader_lock);
      if (p) {
            if (!preclaim_oss)
                  __unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
                                  p->name);
            device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
            kfree(p);
      }
}

/*
 *    Allocations
 *
 *    0     *16         Mixers
 *    1     *8          Sequencers
 *    2     *16         Midi
 *    3     *16         DSP
 *    4     *16         SunDSP
 *    5     *16         DSP16
 *    6     --          sndstat (obsolete)
 *    7     *16         unused
 *    8     --          alternate sequencer (see above)
 *    9     *16         raw synthesizer access
 *    10    *16         unused
 *    11    *16         unused
 *    12    *16         unused
 *    13    *16         unused
 *    14    *16         unused
 *    15    *16         unused
 */

static struct sound_unit *chains[SOUND_STEP];

/**
 *    register_sound_special_device - register a special sound node
 *    @fops: File operations for the driver
 *    @unit: Unit number to allocate
 *      @dev: device pointer
 *
 *    Allocate a special sound device by minor number from the sound
 *    subsystem. The allocated number is returned on success. On failure
 *    a negative error code is returned.
 */
 
int register_sound_special_device(const struct file_operations *fops, int unit,
                          struct device *dev)
{
      const int chain = unit % SOUND_STEP;
      int max_unit = 128 + chain;
      const char *name;
      char _name[16];

      switch (chain) {
          case 0:
            name = "mixer";
            break;
          case 1:
            name = "sequencer";
            if (unit >= SOUND_STEP)
                  goto __unknown;
            max_unit = unit + 1;
            break;
          case 2:
            name = "midi";
            break;
          case 3:
            name = "dsp";
            break;
          case 4:
            name = "audio";
            break;
          case 8:
            name = "sequencer2";
            if (unit >= SOUND_STEP)
                  goto __unknown;
            max_unit = unit + 1;
            break;
          case 9:
            name = "dmmidi";
            break;
          case 10:
            name = "dmfm";
            break;
          case 12:
            name = "adsp";
            break;
          case 13:
            name = "amidi";
            break;
          case 14:
            name = "admmidi";
            break;
          default:
            {
                __unknown:
                  sprintf(_name, "unknown%d", chain);
                  if (unit >= SOUND_STEP)
                        strcat(_name, "-");
                  name = _name;
            }
            break;
      }
      return sound_insert_unit(&chains[chain], fops, -1, unit, max_unit,
                         name, S_IRUSR | S_IWUSR, dev);
}
 
EXPORT_SYMBOL(register_sound_special_device);

int register_sound_special(const struct file_operations *fops, int unit)
{
      return register_sound_special_device(fops, unit, NULL);
}

EXPORT_SYMBOL(register_sound_special);

/**
 *    register_sound_mixer - register a mixer device
 *    @fops: File operations for the driver
 *    @dev: Unit number to allocate
 *
 *    Allocate a mixer device. Unit is the number of the mixer requested.
 *    Pass -1 to request the next free mixer unit. On success the allocated
 *    number is returned, on failure a negative error code is returned.
 */

int register_sound_mixer(const struct file_operations *fops, int dev)
{
      return sound_insert_unit(&chains[0], fops, dev, 0, 128,
                         "mixer", S_IRUSR | S_IWUSR, NULL);
}

EXPORT_SYMBOL(register_sound_mixer);

/**
 *    register_sound_midi - register a midi device
 *    @fops: File operations for the driver
 *    @dev: Unit number to allocate
 *
 *    Allocate a midi device. Unit is the number of the midi device requested.
 *    Pass -1 to request the next free midi unit. On success the allocated
 *    number is returned, on failure a negative error code is returned.
 */

int register_sound_midi(const struct file_operations *fops, int dev)
{
      return sound_insert_unit(&chains[2], fops, dev, 2, 130,
                         "midi", S_IRUSR | S_IWUSR, NULL);
}

EXPORT_SYMBOL(register_sound_midi);

/*
 *    DSP's are registered as a triple. Register only one and cheat
 *    in open - see below.
 */
 
/**
 *    register_sound_dsp - register a DSP device
 *    @fops: File operations for the driver
 *    @dev: Unit number to allocate
 *
 *    Allocate a DSP device. Unit is the number of the DSP requested.
 *    Pass -1 to request the next free DSP unit. On success the allocated
 *    number is returned, on failure a negative error code is returned.
 *
 *    This function allocates both the audio and dsp device entries together
 *    and will always allocate them as a matching pair - eg dsp3/audio3
 */

int register_sound_dsp(const struct file_operations *fops, int dev)
{
      return sound_insert_unit(&chains[3], fops, dev, 3, 131,
                         "dsp", S_IWUSR | S_IRUSR, NULL);
}

EXPORT_SYMBOL(register_sound_dsp);

/**
 *    unregister_sound_special - unregister a special sound device
 *    @unit: unit number to allocate
 *
 *    Release a sound device that was allocated with
 *    register_sound_special(). The unit passed is the return value from
 *    the register function.
 */


void unregister_sound_special(int unit)
{
      sound_remove_unit(&chains[unit % SOUND_STEP], unit);
}
 
EXPORT_SYMBOL(unregister_sound_special);

/**
 *    unregister_sound_mixer - unregister a mixer
 *    @unit: unit number to allocate
 *
 *    Release a sound device that was allocated with register_sound_mixer().
 *    The unit passed is the return value from the register function.
 */

void unregister_sound_mixer(int unit)
{
      sound_remove_unit(&chains[0], unit);
}

EXPORT_SYMBOL(unregister_sound_mixer);

/**
 *    unregister_sound_midi - unregister a midi device
 *    @unit: unit number to allocate
 *
 *    Release a sound device that was allocated with register_sound_midi().
 *    The unit passed is the return value from the register function.
 */

void unregister_sound_midi(int unit)
{
      sound_remove_unit(&chains[2], unit);
}

EXPORT_SYMBOL(unregister_sound_midi);

/**
 *    unregister_sound_dsp - unregister a DSP device
 *    @unit: unit number to allocate
 *
 *    Release a sound device that was allocated with register_sound_dsp().
 *    The unit passed is the return value from the register function.
 *
 *    Both of the allocated units are released together automatically.
 */

void unregister_sound_dsp(int unit)
{
      sound_remove_unit(&chains[3], unit);
}


EXPORT_SYMBOL(unregister_sound_dsp);

static struct sound_unit *__look_for_unit(int chain, int unit)
{
      struct sound_unit *s;
      
      s=chains[chain];
      while(s && s->unit_minor <= unit)
      {
            if(s->unit_minor==unit)
                  return s;
            s=s->next;
      }
      return NULL;
}

static int soundcore_open(struct inode *inode, struct file *file)
{
      int chain;
      int unit = iminor(inode);
      struct sound_unit *s;
      const struct file_operations *new_fops = NULL;

      chain=unit&0x0F;
      if(chain==4 || chain==5)      /* dsp/audio/dsp16 */
      {
            unit&=0xF0;
            unit|=3;
            chain=3;
      }
      
      spin_lock(&sound_loader_lock);
      s = __look_for_unit(chain, unit);
      if (s)
            new_fops = fops_get(s->unit_fops);
      if (preclaim_oss && !new_fops) {
            spin_unlock(&sound_loader_lock);

            /*
             *  Please, don't change this order or code.
             *  For ALSA slot means soundcard and OSS emulation code
             *  comes as add-on modules which aren't depend on
             *  ALSA toplevel modules for soundcards, thus we need
             *  load them at first.   [Jaroslav Kysela <perex@jcu.cz>]
             */
            request_module("sound-slot-%i", unit>>4);
            request_module("sound-service-%i-%i", unit>>4, chain);

            /*
             * sound-slot/service-* module aliases are scheduled
             * for removal in favor of the standard char-major-*
             * module aliases.  For the time being, generate both
             * the legacy and standard module aliases to ease
             * transition.
             */
            if (request_module("char-major-%d-%d", SOUND_MAJOR, unit) > 0)
                  request_module("char-major-%d", SOUND_MAJOR);

            spin_lock(&sound_loader_lock);
            s = __look_for_unit(chain, unit);
            if (s)
                  new_fops = fops_get(s->unit_fops);
      }
      if (new_fops) {
            /*
             * We rely upon the fact that we can't be unloaded while the
             * subdriver is there, so if ->open() is successful we can
             * safely drop the reference counter and if it is not we can
             * revert to old ->f_op. Ugly, indeed, but that's the cost of
             * switching ->f_op in the first place.
             */
            int err = 0;
            const struct file_operations *old_fops = file->f_op;
            file->f_op = new_fops;
            spin_unlock(&sound_loader_lock);

            if (file->f_op->open)
                  err = file->f_op->open(inode,file);

            if (err) {
                  fops_put(file->f_op);
                  file->f_op = fops_get(old_fops);
            }

            fops_put(old_fops);
            return err;
      }
      spin_unlock(&sound_loader_lock);
      return -ENODEV;
}

MODULE_ALIAS_CHARDEV_MAJOR(SOUND_MAJOR);

static void cleanup_oss_soundcore(void)
{
      /* We have nothing to really do here - we know the lists must be
         empty */
      unregister_chrdev(SOUND_MAJOR, "sound");
}

static int __init init_oss_soundcore(void)
{
      if (preclaim_oss &&
          register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops) == -1) {
            printk(KERN_ERR "soundcore: sound device already in use.\n");
            return -EBUSY;
      }

      return 0;
}

#endif /* CONFIG_SOUND_OSS_CORE */

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