FreeBSD/Linux Kernel Cross Reference
sys/sound/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, umode_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.
    */
   #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 = 256;
           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 5:
                   name = "dspW";
                   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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