Function rpmsgdev_read

drivers/misc/rpmsgdev.c:389–443

 ****************************************************************************/

static ssize_t rpmsgdev_read(FAR struct file *filep, FAR char *buffer,
                             size_t buflen)
{
  FAR struct rpmsgdev_s *dev;
  FAR struct rpmsgdev_priv_s *priv;
  struct rpmsgdev_read_s msg;
  struct iovec read;
  uint32_t command;
  ssize_t ret;

  if (buffer == NULL)
    {
      return -EINVAL;
    }

  /* Recover our private data from the struct file instance */

  dev  = filep->f_inode->i_private;
  priv = filep->f_priv;
  DEBUGASSERT(dev != NULL && priv != NULL);

  /* Call the host to perform the read */

  read.iov_base = buffer;
  read.iov_len  = 0;

  msg.filep = priv->filep;
  msg.count = buflen;
  command   = dev->flags & RPMSGDEV_NOFRAG_READ ?
              RPMSGDEV_READ_NOFRAG : RPMSGDEV_READ;

  for (; ; )
    {
      ret = rpmsgdev_send_recv(dev, command, true, &msg.header,
                               sizeof(msg) - 1, &read);
      if (ret != -EAGAIN || read.iov_len > 0 || priv->nonblock)
        {
          break;
        }

      /* If open with block mode and return -EAGAIN, should wait the
       * perr device ready and try again until read success or some
       * other errors occur.
       */

      ret = rpmsgdev_wait(filep, POLLIN);
      if (ret < 0)
        {
          rpmsgdeverr("read wait failed, ret=%d\n", ret);
          break;
        }
    }

  return read.iov_len ? read.iov_len : ret;
}

/****************************************************************************
 * Name: rpmsgdev_write