/**************************************************************************** * drivers/pipes/fifo.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 #include #include #include #include #include #include "pipe_common.h" #if CONFIG_DEV_FIFO_SIZE > 0 /**************************************************************************** * Private Data ****************************************************************************/ static const struct file_operations g_fifo_fops = { pipecommon_open, /* open */ pipecommon_close, /* close */ pipecommon_read, /* read */ pipecommon_write, /* write */ NULL, /* seek */ pipecommon_ioctl, /* ioctl */ NULL, /* truncate */ NULL, /* mmap */ pipecommon_poll /* poll */ #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS , pipecommon_unlink /* unlink */ #endif }; /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: nx_mkfifo * * Description: * nx_mkfifo() makes a FIFO device driver file with name 'pathname.' Unlike * Linux, a NuttX FIFO is not a special file type but simply a device * driver instance. 'mode' specifies the FIFO's permissions. * * Once the FIFO has been created by nx_mkfifo(), any thread can open it * for reading or writing, in the same way as an ordinary file. However, it * must have been opened from both reading and writing before input or * output can be performed. This FIFO implementation will block all * attempts to open a FIFO read-only until at least one thread has opened * the FIFO for writing. * * If all threads that write to the FIFO have closed, subsequent calls to * read() on the FIFO will return 0 (end-of-file). * * NOTE: nx_mkfifo is a special, non-standard, NuttX-only interface. Since * the NuttX FIFOs are based in in-memory, circular buffers, the ability * to control the size of those buffers is critical for system tuning. * * Input Parameters: * pathname - The full path to the FIFO instance to attach to or to create * (if not already created). * mode - Ignored for now * bufsize - The size of the in-memory, circular buffer in bytes. * * Returned Value: * 0 is returned on success; a negated errno value is returned on a * failure. * ****************************************************************************/ int nx_mkfifo(FAR const char *pathname, mode_t mode, size_t bufsize) { FAR struct pipe_dev_s *dev; int ret; /* Allocate and initialize a new device structure instance */ dev = pipecommon_allocdev(bufsize); if (!dev) { return -ENOMEM; } ret = register_driver(pathname, &g_fifo_fops, mode, (FAR void *)dev); if (ret != 0) { pipecommon_freedev(dev); } return ret; } #endif /* CONFIG_DEV_FIFO_SIZE > 0 */