nuttx/mm/iob/iob_initialize.c

/****************************************************************************
 * mm/iob/iob_initialize.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdbool.h>

#include <nuttx/mm/iob.h>

#include "iob.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef NULL
#  define NULL ((FAR void *)0)
#endif

/****************************************************************************
 * Private Data
 ****************************************************************************/

/* This is a pool of pre-allocated I/O buffers */

static struct iob_s        g_iob_pool[CONFIG_IOB_NBUFFERS];
#if CONFIG_IOB_NCHAINS > 0
static struct iob_qentry_s g_iob_qpool[CONFIG_IOB_NCHAINS];
#endif

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* A list of all free, unallocated I/O buffers */

FAR struct iob_s *g_iob_freelist;

/* A list of I/O buffers that are committed for allocation */

FAR struct iob_s *g_iob_committed;

#if CONFIG_IOB_NCHAINS > 0
/* A list of all free, unallocated I/O buffer queue containers */

FAR struct iob_qentry_s *g_iob_freeqlist;

/* A list of I/O buffer queue containers that are committed for allocation */

FAR struct iob_qentry_s *g_iob_qcommitted;
#endif

/* Counting semaphores that tracks the number of free IOBs/qentries */

sem_t g_iob_sem;            /* Counts free I/O buffers */
#if CONFIG_IOB_THROTTLE > 0
sem_t g_throttle_sem;       /* Counts available I/O buffers when throttled */
#endif
#if CONFIG_IOB_NCHAINS > 0
sem_t g_qentry_sem;         /* Counts free I/O buffer queue containers */
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: iob_initialize
 *
 * Description:
 *   Set up the I/O buffers for normal operations.
 *
 ****************************************************************************/

void iob_initialize(void)
{
  static bool initialized = false;
  int i;

  /* Perform one-time initialization */

  if (!initialized)
    {
      /* Add each I/O buffer to the free list */

      for (i = 0; i < CONFIG_IOB_NBUFFERS; i++)
        {
          FAR struct iob_s *iob = &g_iob_pool[i];

          /* Add the pre-allocate I/O buffer to the head of the free list */

          iob->io_flink  = g_iob_freelist;
          g_iob_freelist = iob;
        }

      g_iob_committed = NULL;

      nxsem_init(&g_iob_sem, 0, CONFIG_IOB_NBUFFERS);
#if CONFIG_IOB_THROTTLE > 0
      nxsem_init(&g_throttle_sem,
                 0,
                 CONFIG_IOB_NBUFFERS - CONFIG_IOB_THROTTLE);
#endif

#if CONFIG_IOB_NCHAINS > 0
      /* Add each I/O buffer chain queue container to the free list */

      for (i = 0; i < CONFIG_IOB_NCHAINS; i++)
        {
          FAR struct iob_qentry_s *iobq = &g_iob_qpool[i];

          /* Add the pre-allocate buffer container to the head of the free
           * list
           */

          iobq->qe_flink  = g_iob_freeqlist;
          g_iob_freeqlist = iobq;
        }

      g_iob_qcommitted = NULL;

      nxsem_init(&g_qentry_sem, 0, CONFIG_IOB_NCHAINS);
#endif

      initialized = true;
    }
}