/**************************************************************************** * drivers/pipes/pipe.c * * Copyright (C) 2008-2009 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Compilation Switches ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include "pipe_common.h" #if CONFIG_DEV_PIPE_SIZE > 0 /**************************************************************************** * Definitions ****************************************************************************/ #define MAX_PIPES 32 /**************************************************************************** * Private Types ****************************************************************************/ /**************************************************************************** * Private Function Prototypes ****************************************************************************/ static int pipe_close(FAR struct file *filep); /**************************************************************************** * Private Data ****************************************************************************/ static const struct file_operations pipe_fops = { pipecommon_open, /* open */ pipe_close, /* close */ pipecommon_read, /* read */ pipecommon_write, /* write */ 0, /* seek */ 0 /* ioctl */ #ifndef CONFIG_DISABLE_POLL , pipecommon_poll /* poll */ #endif }; static sem_t g_pipesem = SEM_INITIALIZER(1); static uint32_t g_pipeset = 0; static uint32_t g_pipecreated = 0; /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: pipe_allocate ****************************************************************************/ static inline int pipe_allocate(void) { int pipeno; int ret = -ENFILE; for (pipeno = 0; pipeno < MAX_PIPES; pipeno++) { if ((g_pipeset & (1 << pipeno)) == 0) { g_pipeset |= (1 << pipeno); ret = pipeno; break; } } return ret; } /**************************************************************************** * Name: pipe_free ****************************************************************************/ static inline void pipe_free(int pipeno) { int ret = sem_wait(&g_pipesem); if (ret == 0) { g_pipeset &= ~(1 << pipeno); (void)sem_post(&g_pipesem); } } /**************************************************************************** * Name: pipe_close ****************************************************************************/ static int pipe_close(FAR struct file *filep) { struct inode *inode = filep->f_inode; struct pipe_dev_s *dev = inode->i_private; int ret; /* Some sanity checking */ #if CONFIG_DEBUG if (!dev) { return -EBADF; } #endif /* Perform common close operations */ ret = pipecommon_close(filep); if (ret == 0 && dev->d_refs == 0) { /* Release the pipe when there are no further open references to it. */ pipe_free(dev->d_pipeno); } return ret; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: pipe * * Description: * pipe() creates a pair of file descriptors, pointing to a pipe inode, and * places them in the array pointed to by 'fd'. fd[0] is for reading, * fd[1] is for writing. * * Inputs: * fd[2] - The user provided array in which to catch the pipe file * descriptors * * Return: * 0 is returned on success; otherwise, -1 is returned with errno set * appropriately. * ****************************************************************************/ int pipe(int fd[2]) { struct pipe_dev_s *dev = NULL; char devname[16]; int pipeno; int err; int ret; /* Get exclusive access to the pipe allocation data */ ret = sem_wait(&g_pipesem); if (ret < 0) { /* sem_wait() will have already set errno */ return ERROR; } /* Allocate a minor number for the pipe device */ pipeno = pipe_allocate(); if (pipeno < 0) { (void)sem_post(&g_pipesem); err = -pipeno; goto errout; } /* Create a pathname to the pipe device */ sprintf(devname, "/dev/pipe%d", pipeno); /* Check if the pipe device has already been created */ if ((g_pipecreated & (1 << pipeno)) == 0) { /* No.. Allocate and initialize a new device structure instance */ dev = pipecommon_allocdev(); if (!dev) { (void)sem_post(&g_pipesem); err = ENOMEM; goto errout_with_pipe; } dev->d_pipeno = pipeno; /* Register the pipe device */ ret = register_driver(devname, &pipe_fops, 0666, (void*)dev); if (ret != 0) { (void)sem_post(&g_pipesem); err = -ret; goto errout_with_dev; } /* Remember that we created this device */ g_pipecreated |= (1 << pipeno); } (void)sem_post(&g_pipesem); /* Get a write file descriptor */ fd[1] = open(devname, O_WRONLY); if (fd[1] < 0) { err = -fd[1]; goto errout_with_driver; } /* Get a read file descriptor */ fd[0] = open(devname, O_RDONLY); if (fd[0] < 0) { err = -fd[0]; goto errout_with_wrfd; } return OK; errout_with_wrfd: close(fd[1]); errout_with_driver: unregister_driver(devname); errout_with_dev: pipecommon_freedev(dev); errout_with_pipe: pipe_free(pipeno); errout: errno = err; return ERROR; } #endif /* CONFIG_DEV_PIPE_SIZE > 0 */