seq_device.c

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/*
 *  ALSA sequencer device management
 *  Copyright (c) 1999 by Takashi Iwai <[email protected]>
 *
 *   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 <linux/module.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 <[email protected]>");
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_MODULES
/* 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_MODULES
    struct ops_list *ops;

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

    if (snd_BUG_ON(!id))
        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;

    if (snd_BUG_ON(!dev))
        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_MODULES
EXPORT_SYMBOL(snd_seq_autoload_lock);
EXPORT_SYMBOL(snd_seq_autoload_unlock);
#endif