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seq_device.c

/*
 *  ALSA sequencer device management
 *  Copyright (c) 1999 by Takashi Iwai <tiwai@suse.de>
 *
 *   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.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 *
 *----------------------------------------------------------------
 *
 * This device handler separates the card driver module from sequencer
 * stuff (sequencer core, synth drivers, etc), so that user can avoid
 * to spend unnecessary resources e.g. if he needs only listening to
 * MP3s.
 *
 * The card (or lowlevel) driver creates a sequencer device entry
 * via snd_seq_device_new().  This is an entry pointer to communicate
 * with the sequencer device "driver", which is involved with the
 * actual part to communicate with the sequencer core.
 * Each sequencer device entry has an id string and the corresponding
 * driver with the same id is loaded when required.  For example,
 * lowlevel codes to access emu8000 chip on sbawe card are included in
 * emu8000-synth module.  To activate this module, the hardware
 * resources like i/o port are passed via snd_seq_device argument.
 *
 */

#include <linux/init.h>
#include <sound/core.h>
#include <sound/info.h>
#include <sound/seq_device.h>
#include <sound/seq_kernel.h>
#include <sound/initval.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/mutex.h>

MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
MODULE_DESCRIPTION("ALSA sequencer device management");
MODULE_LICENSE("GPL");

/* driver state */
#define DRIVER_EMPTY          0
#define DRIVER_LOADED         (1<<0)
#define DRIVER_REQUESTED      (1<<1)
#define DRIVER_LOCKED         (1<<2)

struct ops_list {
      char id[ID_LEN];  /* driver id */
      int driver;       /* driver state */
      int used;         /* reference counter */
      int argsize;            /* argument size */

      /* operators */
      struct snd_seq_dev_ops ops;

      /* registred devices */
      struct list_head dev_list;    /* list of devices */
      int num_devices;  /* number of associated devices */
      int num_init_devices;   /* number of initialized devices */
      struct mutex reg_mutex;

      struct list_head list;  /* next driver */
};


static LIST_HEAD(opslist);
static int num_ops;
static DEFINE_MUTEX(ops_mutex);
#ifdef CONFIG_PROC_FS
static struct snd_info_entry *info_entry;
#endif

/*
 * prototypes
 */
static int snd_seq_device_free(struct snd_seq_device *dev);
static int snd_seq_device_dev_free(struct snd_device *device);
static int snd_seq_device_dev_register(struct snd_device *device);
static int snd_seq_device_dev_disconnect(struct snd_device *device);

static int init_device(struct snd_seq_device *dev, struct ops_list *ops);
static int free_device(struct snd_seq_device *dev, struct ops_list *ops);
static struct ops_list *find_driver(char *id, int create_if_empty);
static struct ops_list *create_driver(char *id);
static void unlock_driver(struct ops_list *ops);
static void remove_drivers(void);

/*
 * show all drivers and their status
 */

#ifdef CONFIG_PROC_FS
static void snd_seq_device_info(struct snd_info_entry *entry,
                        struct snd_info_buffer *buffer)
{
      struct ops_list *ops;

      mutex_lock(&ops_mutex);
      list_for_each_entry(ops, &opslist, list) {
            snd_iprintf(buffer, "snd-%s%s%s%s,%d\n",
                        ops->id,
                        ops->driver & DRIVER_LOADED ? ",loaded" : (ops->driver == DRIVER_EMPTY ? ",empty" : ""),
                        ops->driver & DRIVER_REQUESTED ? ",requested" : "",
                        ops->driver & DRIVER_LOCKED ? ",locked" : "",
                        ops->num_devices);
      }
      mutex_unlock(&ops_mutex);
}
#endif
 
/*
 * load all registered drivers (called from seq_clientmgr.c)
 */

#ifdef CONFIG_KMOD
/* avoid auto-loading during module_init() */
static int snd_seq_in_init;
void snd_seq_autoload_lock(void)
{
      snd_seq_in_init++;
}

void snd_seq_autoload_unlock(void)
{
      snd_seq_in_init--;
}
#endif

void snd_seq_device_load_drivers(void)
{
#ifdef CONFIG_KMOD
      struct ops_list *ops;

      /* Calling request_module during module_init()
       * may cause blocking.
       */
      if (snd_seq_in_init)
            return;

      if (! current->fs->root)
            return;

      mutex_lock(&ops_mutex);
      list_for_each_entry(ops, &opslist, list) {
            if (! (ops->driver & DRIVER_LOADED) &&
                ! (ops->driver & DRIVER_REQUESTED)) {
                  ops->used++;
                  mutex_unlock(&ops_mutex);
                  ops->driver |= DRIVER_REQUESTED;
                  request_module("snd-%s", ops->id);
                  mutex_lock(&ops_mutex);
                  ops->used--;
            }
      }
      mutex_unlock(&ops_mutex);
#endif
}

/*
 * register a sequencer device
 * card = card info (NULL allowed)
 * device = device number (if any)
 * id = id of driver
 * result = return pointer (NULL allowed if unnecessary)
 */
int snd_seq_device_new(struct snd_card *card, int device, char *id, int argsize,
                   struct snd_seq_device **result)
{
      struct snd_seq_device *dev;
      struct ops_list *ops;
      int err;
      static struct snd_device_ops dops = {
            .dev_free = snd_seq_device_dev_free,
            .dev_register = snd_seq_device_dev_register,
            .dev_disconnect = snd_seq_device_dev_disconnect,
      };

      if (result)
            *result = NULL;

      snd_assert(id != NULL, return -EINVAL);

      ops = find_driver(id, 1);
      if (ops == NULL)
            return -ENOMEM;

      dev = kzalloc(sizeof(*dev)*2 + argsize, GFP_KERNEL);
      if (dev == NULL) {
            unlock_driver(ops);
            return -ENOMEM;
      }

      /* set up device info */
      dev->card = card;
      dev->device = device;
      strlcpy(dev->id, id, sizeof(dev->id));
      dev->argsize = argsize;
      dev->status = SNDRV_SEQ_DEVICE_FREE;

      /* add this device to the list */
      mutex_lock(&ops->reg_mutex);
      list_add_tail(&dev->list, &ops->dev_list);
      ops->num_devices++;
      mutex_unlock(&ops->reg_mutex);

      unlock_driver(ops);
      
      if ((err = snd_device_new(card, SNDRV_DEV_SEQUENCER, dev, &dops)) < 0) {
            snd_seq_device_free(dev);
            return err;
      }
      
      if (result)
            *result = dev;

      return 0;
}

/*
 * free the existing device
 */
static int snd_seq_device_free(struct snd_seq_device *dev)
{
      struct ops_list *ops;

      snd_assert(dev != NULL, return -EINVAL);

      ops = find_driver(dev->id, 0);
      if (ops == NULL)
            return -ENXIO;

      /* remove the device from the list */
      mutex_lock(&ops->reg_mutex);
      list_del(&dev->list);
      ops->num_devices--;
      mutex_unlock(&ops->reg_mutex);

      free_device(dev, ops);
      if (dev->private_free)
            dev->private_free(dev);
      kfree(dev);

      unlock_driver(ops);

      return 0;
}

static int snd_seq_device_dev_free(struct snd_device *device)
{
      struct snd_seq_device *dev = device->device_data;
      return snd_seq_device_free(dev);
}

/*
 * register the device
 */
static int snd_seq_device_dev_register(struct snd_device *device)
{
      struct snd_seq_device *dev = device->device_data;
      struct ops_list *ops;

      ops = find_driver(dev->id, 0);
      if (ops == NULL)
            return -ENOENT;

      /* initialize this device if the corresponding driver was
       * already loaded
       */
      if (ops->driver & DRIVER_LOADED)
            init_device(dev, ops);

      unlock_driver(ops);
      return 0;
}

/*
 * disconnect the device
 */
static int snd_seq_device_dev_disconnect(struct snd_device *device)
{
      struct snd_seq_device *dev = device->device_data;
      struct ops_list *ops;

      ops = find_driver(dev->id, 0);
      if (ops == NULL)
            return -ENOENT;

      free_device(dev, ops);

      unlock_driver(ops);
      return 0;
}

/*
 * register device driver
 * id = driver id
 * entry = driver operators - duplicated to each instance
 */
int snd_seq_device_register_driver(char *id, struct snd_seq_dev_ops *entry,
                           int argsize)
{
      struct ops_list *ops;
      struct snd_seq_device *dev;

      if (id == NULL || entry == NULL ||
          entry->init_device == NULL || entry->free_device == NULL)
            return -EINVAL;

      snd_seq_autoload_lock();
      ops = find_driver(id, 1);
      if (ops == NULL) {
            snd_seq_autoload_unlock();
            return -ENOMEM;
      }
      if (ops->driver & DRIVER_LOADED) {
            snd_printk(KERN_WARNING "driver_register: driver '%s' already exists\n", id);
            unlock_driver(ops);
            snd_seq_autoload_unlock();
            return -EBUSY;
      }

      mutex_lock(&ops->reg_mutex);
      /* copy driver operators */
      ops->ops = *entry;
      ops->driver |= DRIVER_LOADED;
      ops->argsize = argsize;

      /* initialize existing devices if necessary */
      list_for_each_entry(dev, &ops->dev_list, list) {
            init_device(dev, ops);
      }
      mutex_unlock(&ops->reg_mutex);

      unlock_driver(ops);
      snd_seq_autoload_unlock();

      return 0;
}


/*
 * create driver record
 */
static struct ops_list * create_driver(char *id)
{
      struct ops_list *ops;

      ops = kzalloc(sizeof(*ops), GFP_KERNEL);
      if (ops == NULL)
            return ops;

      /* set up driver entry */
      strlcpy(ops->id, id, sizeof(ops->id));
      mutex_init(&ops->reg_mutex);
      /*
       * The ->reg_mutex locking rules are per-driver, so we create
       * separate per-driver lock classes:
       */
      lockdep_set_class(&ops->reg_mutex, (struct lock_class_key *)id);

      ops->driver = DRIVER_EMPTY;
      INIT_LIST_HEAD(&ops->dev_list);
      /* lock this instance */
      ops->used = 1;

      /* register driver entry */
      mutex_lock(&ops_mutex);
      list_add_tail(&ops->list, &opslist);
      num_ops++;
      mutex_unlock(&ops_mutex);

      return ops;
}


/*
 * unregister the specified driver
 */
int snd_seq_device_unregister_driver(char *id)
{
      struct ops_list *ops;
      struct snd_seq_device *dev;

      ops = find_driver(id, 0);
      if (ops == NULL)
            return -ENXIO;
      if (! (ops->driver & DRIVER_LOADED) ||
          (ops->driver & DRIVER_LOCKED)) {
            snd_printk(KERN_ERR "driver_unregister: cannot unload driver '%s': status=%x\n",
                     id, ops->driver);
            unlock_driver(ops);
            return -EBUSY;
      }

      /* close and release all devices associated with this driver */
      mutex_lock(&ops->reg_mutex);
      ops->driver |= DRIVER_LOCKED; /* do not remove this driver recursively */
      list_for_each_entry(dev, &ops->dev_list, list) {
            free_device(dev, ops);
      }

      ops->driver = 0;
      if (ops->num_init_devices > 0)
            snd_printk(KERN_ERR "free_driver: init_devices > 0!! (%d)\n",
                     ops->num_init_devices);
      mutex_unlock(&ops->reg_mutex);

      unlock_driver(ops);

      /* remove empty driver entries */
      remove_drivers();

      return 0;
}


/*
 * remove empty driver entries
 */
static void remove_drivers(void)
{
      struct list_head *head;

      mutex_lock(&ops_mutex);
      head = opslist.next;
      while (head != &opslist) {
            struct ops_list *ops = list_entry(head, struct ops_list, list);
            if (! (ops->driver & DRIVER_LOADED) &&
                ops->used == 0 && ops->num_devices == 0) {
                  head = head->next;
                  list_del(&ops->list);
                  kfree(ops);
                  num_ops--;
            } else
                  head = head->next;
      }
      mutex_unlock(&ops_mutex);
}

/*
 * initialize the device - call init_device operator
 */
static int init_device(struct snd_seq_device *dev, struct ops_list *ops)
{
      if (! (ops->driver & DRIVER_LOADED))
            return 0; /* driver is not loaded yet */
      if (dev->status != SNDRV_SEQ_DEVICE_FREE)
            return 0; /* already initialized */
      if (ops->argsize != dev->argsize) {
            snd_printk(KERN_ERR "incompatible device '%s' for plug-in '%s' (%d %d)\n",
                     dev->name, ops->id, ops->argsize, dev->argsize);
            return -EINVAL;
      }
      if (ops->ops.init_device(dev) >= 0) {
            dev->status = SNDRV_SEQ_DEVICE_REGISTERED;
            ops->num_init_devices++;
      } else {
            snd_printk(KERN_ERR "init_device failed: %s: %s\n",
                     dev->name, dev->id);
      }

      return 0;
}

/*
 * release the device - call free_device operator
 */
static int free_device(struct snd_seq_device *dev, struct ops_list *ops)
{
      int result;

      if (! (ops->driver & DRIVER_LOADED))
            return 0; /* driver is not loaded yet */
      if (dev->status != SNDRV_SEQ_DEVICE_REGISTERED)
            return 0; /* not registered */
      if (ops->argsize != dev->argsize) {
            snd_printk(KERN_ERR "incompatible device '%s' for plug-in '%s' (%d %d)\n",
                     dev->name, ops->id, ops->argsize, dev->argsize);
            return -EINVAL;
      }
      if ((result = ops->ops.free_device(dev)) >= 0 || result == -ENXIO) {
            dev->status = SNDRV_SEQ_DEVICE_FREE;
            dev->driver_data = NULL;
            ops->num_init_devices--;
      } else {
            snd_printk(KERN_ERR "free_device failed: %s: %s\n",
                     dev->name, dev->id);
      }

      return 0;
}

/*
 * find the matching driver with given id
 */
static struct ops_list * find_driver(char *id, int create_if_empty)
{
      struct ops_list *ops;

      mutex_lock(&ops_mutex);
      list_for_each_entry(ops, &opslist, list) {
            if (strcmp(ops->id, id) == 0) {
                  ops->used++;
                  mutex_unlock(&ops_mutex);
                  return ops;
            }
      }
      mutex_unlock(&ops_mutex);
      if (create_if_empty)
            return create_driver(id);
      return NULL;
}

static void unlock_driver(struct ops_list *ops)
{
      mutex_lock(&ops_mutex);
      ops->used--;
      mutex_unlock(&ops_mutex);
}


/*
 * module part
 */

static int __init alsa_seq_device_init(void)
{
#ifdef CONFIG_PROC_FS
      info_entry = snd_info_create_module_entry(THIS_MODULE, "drivers",
                                      snd_seq_root);
      if (info_entry == NULL)
            return -ENOMEM;
      info_entry->content = SNDRV_INFO_CONTENT_TEXT;
      info_entry->c.text.read = snd_seq_device_info;
      if (snd_info_register(info_entry) < 0) {
            snd_info_free_entry(info_entry);
            return -ENOMEM;
      }
#endif
      return 0;
}

static void __exit alsa_seq_device_exit(void)
{
      remove_drivers();
#ifdef CONFIG_PROC_FS
      snd_info_free_entry(info_entry);
#endif
      if (num_ops)
            snd_printk(KERN_ERR "drivers not released (%d)\n", num_ops);
}

module_init(alsa_seq_device_init)
module_exit(alsa_seq_device_exit)

EXPORT_SYMBOL(snd_seq_device_load_drivers);
EXPORT_SYMBOL(snd_seq_device_new);
EXPORT_SYMBOL(snd_seq_device_register_driver);
EXPORT_SYMBOL(snd_seq_device_unregister_driver);
#ifdef CONFIG_KMOD
EXPORT_SYMBOL(snd_seq_autoload_lock);
EXPORT_SYMBOL(snd_seq_autoload_unlock);
#endif

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