seq_fifo.c

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/*
 *   ALSA sequencer FIFO
 *   Copyright (c) 1998 by Frank van de Pol <[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
 *
 */

#include <sound/core.h>
#include <linux/slab.h>
#include "seq_fifo.h"
#include "seq_lock.h"


/* FIFO */

/* create new fifo */
struct snd_seq_fifo *snd_seq_fifo_new(int poolsize)
{
    struct snd_seq_fifo *f;

    f = kzalloc(sizeof(*f), GFP_KERNEL);
    if (f == NULL) {
        snd_printd("malloc failed for snd_seq_fifo_new() \n");
        return NULL;
    }

    f->pool = snd_seq_pool_new(poolsize);
    if (f->pool == NULL) {
        kfree(f);
        return NULL;
    }
    if (snd_seq_pool_init(f->pool) < 0) {
        snd_seq_pool_delete(&f->pool);
        kfree(f);
        return NULL;
    }

    spin_lock_init(&f->lock);
    snd_use_lock_init(&f->use_lock);
    init_waitqueue_head(&f->input_sleep);
    atomic_set(&f->overflow, 0);

    f->head = NULL;
    f->tail = NULL;
    f->cells = 0;
    
    return f;
}

void snd_seq_fifo_delete(struct snd_seq_fifo **fifo)
{
    struct snd_seq_fifo *f;

    if (snd_BUG_ON(!fifo))
        return;
    f = *fifo;
    if (snd_BUG_ON(!f))
        return;
    *fifo = NULL;

    snd_seq_fifo_clear(f);

    /* wake up clients if any */
    if (waitqueue_active(&f->input_sleep))
        wake_up(&f->input_sleep);

    /* release resources...*/
    /*....................*/

    if (f->pool) {
        snd_seq_pool_done(f->pool);
        snd_seq_pool_delete(&f->pool);
    }
    
    kfree(f);
}

static struct snd_seq_event_cell *fifo_cell_out(struct snd_seq_fifo *f);

/* clear queue */
void snd_seq_fifo_clear(struct snd_seq_fifo *f)
{
    struct snd_seq_event_cell *cell;
    unsigned long flags;

    /* clear overflow flag */
    atomic_set(&f->overflow, 0);

    snd_use_lock_sync(&f->use_lock);
    spin_lock_irqsave(&f->lock, flags);
    /* drain the fifo */
    while ((cell = fifo_cell_out(f)) != NULL) {
        snd_seq_cell_free(cell);
    }
    spin_unlock_irqrestore(&f->lock, flags);
}


/* enqueue event to fifo */
int snd_seq_fifo_event_in(struct snd_seq_fifo *f,
              struct snd_seq_event *event)
{
    struct snd_seq_event_cell *cell;
    unsigned long flags;
    int err;

    if (snd_BUG_ON(!f))
        return -EINVAL;

    snd_use_lock_use(&f->use_lock);
    err = snd_seq_event_dup(f->pool, event, &cell, 1, NULL); /* always non-blocking */
    if (err < 0) {
        if (err == -ENOMEM)
            atomic_inc(&f->overflow);
        snd_use_lock_free(&f->use_lock);
        return err;
    }
        
    /* append new cells to fifo */
    spin_lock_irqsave(&f->lock, flags);
    if (f->tail != NULL)
        f->tail->next = cell;
    f->tail = cell;
    if (f->head == NULL)
        f->head = cell;
    f->cells++;
    spin_unlock_irqrestore(&f->lock, flags);

    /* wakeup client */
    if (waitqueue_active(&f->input_sleep))
        wake_up(&f->input_sleep);

    snd_use_lock_free(&f->use_lock);

    return 0; /* success */

}

/* dequeue cell from fifo */
static struct snd_seq_event_cell *fifo_cell_out(struct snd_seq_fifo *f)
{
    struct snd_seq_event_cell *cell;

    if ((cell = f->head) != NULL) {
        f->head = cell->next;

        /* reset tail if this was the last element */
        if (f->tail == cell)
            f->tail = NULL;

        cell->next = NULL;
        f->cells--;
    }

    return cell;
}

/* dequeue cell from fifo and copy on user space */
int snd_seq_fifo_cell_out(struct snd_seq_fifo *f,
              struct snd_seq_event_cell **cellp, int nonblock)
{
    struct snd_seq_event_cell *cell;
    unsigned long flags;
    wait_queue_t wait;

    if (snd_BUG_ON(!f))
        return -EINVAL;

    *cellp = NULL;
    init_waitqueue_entry(&wait, current);
    spin_lock_irqsave(&f->lock, flags);
    while ((cell = fifo_cell_out(f)) == NULL) {
        if (nonblock) {
            /* non-blocking - return immediately */
            spin_unlock_irqrestore(&f->lock, flags);
            return -EAGAIN;
        }
        set_current_state(TASK_INTERRUPTIBLE);
        add_wait_queue(&f->input_sleep, &wait);
        spin_unlock_irq(&f->lock);
        schedule();
        spin_lock_irq(&f->lock);
        remove_wait_queue(&f->input_sleep, &wait);
        if (signal_pending(current)) {
            spin_unlock_irqrestore(&f->lock, flags);
            return -ERESTARTSYS;
        }
    }
    spin_unlock_irqrestore(&f->lock, flags);
    *cellp = cell;

    return 0;
}


void snd_seq_fifo_cell_putback(struct snd_seq_fifo *f,
                   struct snd_seq_event_cell *cell)
{
    unsigned long flags;

    if (cell) {
        spin_lock_irqsave(&f->lock, flags);
        cell->next = f->head;
        f->head = cell;
        f->cells++;
        spin_unlock_irqrestore(&f->lock, flags);
    }
}


/* polling; return non-zero if queue is available */
int snd_seq_fifo_poll_wait(struct snd_seq_fifo *f, struct file *file,
               poll_table *wait)
{
    poll_wait(file, &f->input_sleep, wait);
    return (f->cells > 0);
}

/* change the size of pool; all old events are removed */
int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize)
{
    unsigned long flags;
    struct snd_seq_pool *newpool, *oldpool;
    struct snd_seq_event_cell *cell, *next, *oldhead;

    if (snd_BUG_ON(!f || !f->pool))
        return -EINVAL;

    /* allocate new pool */
    newpool = snd_seq_pool_new(poolsize);
    if (newpool == NULL)
        return -ENOMEM;
    if (snd_seq_pool_init(newpool) < 0) {
        snd_seq_pool_delete(&newpool);
        return -ENOMEM;
    }

    spin_lock_irqsave(&f->lock, flags);
    /* remember old pool */
    oldpool = f->pool;
    oldhead = f->head;
    /* exchange pools */
    f->pool = newpool;
    f->head = NULL;
    f->tail = NULL;
    f->cells = 0;
    /* NOTE: overflow flag is not cleared */
    spin_unlock_irqrestore(&f->lock, flags);

    /* release cells in old pool */
    for (cell = oldhead; cell; cell = next) {
        next = cell->next;
        snd_seq_cell_free(cell);
    }
    snd_seq_pool_delete(&oldpool);

    return 0;
}