// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   ALSA sequencer FIFO
 *   Copyright (c) 1998 by Frank van de Pol <fvdpol@coil.demon.nl>
 */

#include <sound/core.h>
#include <linux/slab.h>
#include <linux/sched/signal.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)
                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;

        if (f->pool)
                snd_seq_pool_mark_closing(f->pool);

        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;

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

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


/* 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;
        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, NULL); /* always non-blocking */
        if (err < 0) {
                if ((err == -ENOMEM) || (err == -EAGAIN))
                        atomic_inc(&f->overflow);
                snd_use_lock_free(&f->use_lock);
                return err;
        }
                
        /* append new cells to fifo */
        scoped_guard(spinlock_irqsave, &f->lock) {
                if (f->tail != NULL)
                        f->tail->next = cell;
                f->tail = cell;
                if (f->head == NULL)
                        f->head = cell;
                cell->next = NULL;
                f->cells++;
        }

        /* 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;

        cell = f->head;
        if (cell) {
                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_entry_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_irqrestore(&f->lock, flags);
                schedule();
                spin_lock_irqsave(&f->lock, flags);
                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)
{
        if (cell) {
                guard(spinlock_irqsave)(&f->lock);
                cell->next = f->head;
                f->head = cell;
                if (!f->tail)
                        f->tail = cell;
                f->cells++;
        }
}


/* 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)
{
        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;
        }

        scoped_guard(spinlock_irq, &f->lock) {
                /* 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 */
        }

        /* close the old pool and wait until all users are gone */
        snd_seq_pool_mark_closing(oldpool);
        snd_use_lock_sync(&f->use_lock);

        /* 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;
}

/* get the number of unused cells safely */
int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f)
{
        int cells;

        if (!f)
                return 0;

        snd_use_lock_use(&f->use_lock);
        scoped_guard(spinlock_irqsave, &f->lock)
                cells = snd_seq_unused_cells(f->pool);
        snd_use_lock_free(&f->use_lock);
        return cells;
}