drivers/spi/spi_driver.c

/****************************************************************************
 * drivers/spi/spi_driver.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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 <sys/types.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/mutex.h>
#include <nuttx/spi/spi_transfer.h>

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

/* Device naming ************************************************************/

#define DEVNAME_FMT    "/dev/spi%d"
#define DEVNAME_FMTLEN (8 + 3 + 1)

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* Driver state structure */

struct spi_driver_s
{
  FAR struct spi_dev_s *spi;  /* Contained SPI lower half driver */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  mutex_t lock;               /* Mutual exclusion */
  int16_t crefs;              /* Number of open references */
  bool unlinked;              /* True, driver has been unlinked */
#endif
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int     spidrvr_open(FAR struct file *filep);
static int     spidrvr_close(FAR struct file *filep);
#endif
static ssize_t spidrvr_read(FAR struct file *filep, FAR char *buffer,
                 size_t buflen);
static ssize_t spidrvr_write(FAR struct file *filep, FAR const char *buffer,
                 size_t buflen);
static int     spidrvr_ioctl(FAR struct file *filep, int cmd,
                 unsigned long arg);
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int     spidrvr_unlink(FAR struct inode *inode);
#endif

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

static const struct file_operations g_spidrvr_fops =
{
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  spidrvr_open,    /* open */
  spidrvr_close,   /* close */
#else
  NULL,            /* open */
  NULL,            /* close */
#endif
  spidrvr_read,    /* read */
  spidrvr_write,   /* write */
  NULL,            /* seek */
  spidrvr_ioctl,   /* ioctl */
  NULL,            /* mmap */
  NULL,            /* truncate */
  NULL,            /* poll */
  NULL,            /* readv */
  NULL             /* writev */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  , spidrvr_unlink /* unlink */
#endif
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: spidrvr_open
 ****************************************************************************/

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int spidrvr_open(FAR struct file *filep)
{
  FAR struct spi_driver_s *priv;
  int ret;

  /* Sanity check */

  DEBUGASSERT(filep->f_inode->i_private != NULL);

  /* Get our private data structure */

  priv = filep->f_inode->i_private;

  /* Get exclusive access to the SPI driver state structure */

  ret = nxmutex_lock(&priv->lock);
  if (ret < 0)
    {
      return ret;
    }

  /* Increment the count of open references on the driver */

  priv->crefs++;
  DEBUGASSERT(priv->crefs > 0);

  nxmutex_unlock(&priv->lock);
  return OK;
}
#endif

/****************************************************************************
 * Name: spidrvr_close
 ****************************************************************************/

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int spidrvr_close(FAR struct file *filep)
{
  FAR struct spi_driver_s *priv;
  int ret;

  /* Sanity check */

  DEBUGASSERT(filep->f_inode->i_private != NULL);

  /* Get our private data structure */

  priv = filep->f_inode->i_private;

  /* Get exclusive access to the SPI driver state structure */

  ret = nxmutex_lock(&priv->lock);
  if (ret < 0)
    {
      return ret;
    }

  /* Decrement the count of open references on the driver */

  DEBUGASSERT(priv->crefs > 0);
  priv->crefs--;

  /* If the count has decremented to zero and the driver has been unlinked,
   * then commit Hara-Kiri now.
   */

  if (priv->crefs <= 0 && priv->unlinked)
    {
      nxmutex_destroy(&priv->lock);
      kmm_free(priv);
      filep->f_inode->i_private = NULL;
      return OK;
    }

  nxmutex_unlock(&priv->lock);
  return OK;
}
#endif

/****************************************************************************
 * Name: spidrvr_read
 ****************************************************************************/

static ssize_t spidrvr_read(FAR struct file *filep, FAR char *buffer,
                            size_t len)
{
  return 0; /* Return EOF */
}

/****************************************************************************
 * Name: spidrvr_write
 ****************************************************************************/

static ssize_t spidrvr_write(FAR struct file *filep, FAR const char *buffer,
                             size_t len)
{
  return len; /* Say that everything was written */
}

/****************************************************************************
 * Name: spidrvr_ioctl
 ****************************************************************************/

static int spidrvr_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
  FAR struct spi_driver_s *priv;
  FAR struct spi_sequence_s *seq;
  int ret;

  /* Sanity check */

  DEBUGASSERT(filep->f_inode->i_private != NULL);
  spiinfo("cmd=%d arg=%lu\n", cmd, arg);

  /* Get our private data structure */

  priv = filep->f_inode->i_private;

  /* Get exclusive access to the SPI driver state structure */

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  ret = nxmutex_lock(&priv->lock);
  if (ret < 0)
    {
      return ret;
    }
#endif

  /* Process the IOCTL command */

  switch (cmd)
    {
      /* Command:      SPIIOC_TRANSFER
       * Description:  Perform a sequence of SPI transfers
       * Argument:     A reference to an instance of struct spi_sequence_s.
       * Dependencies: CONFIG_SPI_DRIVER
       */

      case SPIIOC_TRANSFER:
        {
          /* Get the reference to the spi_transfer_s structure */

          seq = (FAR struct spi_sequence_s *)((uintptr_t)arg);
          DEBUGASSERT(seq != NULL);

          /* Perform the transfer */

          ret = spi_transfer(priv->spi, seq);
        }
        break;

      default:
        ret = -ENOTTY;
        break;
    }

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  nxmutex_unlock(&priv->lock);
#endif
  return ret;
}

/****************************************************************************
 * Name: spidrvr_unlink
 ****************************************************************************/

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int spidrvr_unlink(FAR struct inode *inode)
{
  FAR struct spi_driver_s *priv;
  int ret;

  /* Get our private data structure */

  DEBUGASSERT(inode->i_private != NULL);
  priv = inode->i_private;

  /* Get exclusive access to the SPI driver state structure */

  ret = nxmutex_lock(&priv->lock);
  if (ret < 0)
    {
      return ret;
    }

  /* Are there open references to the driver data structure? */

  if (priv->crefs <= 0)
    {
      nxmutex_destroy(&priv->lock);
      kmm_free(priv);
      inode->i_private = NULL;
      return OK;
    }

  /* No... just mark the driver as unlinked and free the resources when the
   * last client closes their reference to the driver.
   */

  priv->unlinked = true;
  nxmutex_unlock(&priv->lock);
  return ret;
}
#endif

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

/****************************************************************************
 * Name: spi_register
 *
 * Description:
 *   Create and register the SPI character driver.
 *
 *   The SPI character driver is a simple character driver that supports SPI
 *   transfers.  The intent of this driver is to support SPI testing.  It is
 *   not suitable for use in any real driver application.
 *
 * Input Parameters:
 *   spi - An instance of the lower half SPI driver
 *   bus - The SPI bus number.  This will be used as the SPI device minor
 *     number.  The SPI character device will be registered as /dev/spiN
 *     where N is the minor number
 *
 * Returned Value:
 *   OK if the driver was successfully register; A negated errno value is
 *   returned on any failure.
 *
 ****************************************************************************/

int spi_register(FAR struct spi_dev_s *spi, int bus)
{
  FAR struct spi_driver_s *priv;
  char devname[DEVNAME_FMTLEN];
  int ret;

  /* Sanity check */

  DEBUGASSERT(spi != NULL && (unsigned)bus < 1000);

  /* Allocate a SPI character device structure */

  priv = kmm_zalloc(sizeof(struct spi_driver_s));
  if (priv)
    {
      /* Initialize the SPI character device structure */

      priv->spi = spi;
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
      nxmutex_init(&priv->lock);
#endif

      /* Create the character device name */

      snprintf(devname, sizeof(devname), DEVNAME_FMT, bus);
      ret = register_driver(devname, &g_spidrvr_fops, 0666, priv);
      if (ret < 0)
        {
          /* Free the device structure if we failed to create the character
           * device.
           */

#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
          nxmutex_destroy(&priv->lock);
#endif
          kmm_free(priv);
          return ret;
        }

      /* Return the result of the registration */

      return ret;
    }

  return -ENOMEM;
}