/****************************************************************************
* drivers/fifo.c
*
* Copyright (C) 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 <nuttx/config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <semaphore.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/fs.h>
#ifndef CONFIG_DEV_FIFO_SIZE
# define CONFIG_DEV_FIFO_SIZE 1024
#endif
#if CONFIG_DEV_FIFO_SIZE > 0
/****************************************************************************
* Definitions
****************************************************************************/
/* Maximum number of open's supported on FIFO */
#define CONFIG_DEV_FIFO_MAXUSER 255
/****************************************************************************
* Private Types
****************************************************************************/
/* Make the FIFO index as small as possible for the configured FIFO size */
#if CONFIG_DEV_FIFO_SIZE > 65535
typedef uint32 fifo_ndx_t; /* 32-bit index */
#elif CONFIG_DEV_FIFO_SIZE > 255
typedef uint16 fifo_ndx_t; /* 16-bit index */
#else
typedef ubyte fifo_ndx_t; /* 8-bit index */
#endif
struct fifo_dev_s
{
sem_t d_bfsem; /* Used to serialize access to d_buffer and indices */
sem_t d_rdsem; /* Empty buffer - Reader waits for data write */
sem_t d_wrsem; /* Full buffer - Writer waits for data read */
fifo_ndx_t d_wrndx; /* Index in d_buffer to save next byte written */
fifo_ndx_t d_rdndx; /* Index in d_buffer to return the next byte read */
ubyte d_refs; /* References counts on FIFO (limited to 255) */
ubyte d_nreaders; /* Number of readers waiting for write data to empty buffer */
ubyte d_nwriters; /* Number of writers wiating for data read out of full buffer */
ubyte d_buffer[CONFIG_DEV_FIFO_SIZE];
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static inline FAR struct fifo_dev_s *fifo_allocdev(void);
static inline void fifo_freedev(FAR struct fifo_dev_s *dev);
static void fifo_semtake(sem_t *sem);
static int fifo_open(FAR struct file *filep);
static int fifo_close(FAR struct file *filep);
static ssize_t fifo_read(FAR struct file *, FAR char *, size_t);
static ssize_t fifo_write(FAR struct file *, FAR const char *, size_t);
/****************************************************************************
* Private Data
****************************************************************************/
static struct file_operations fifo_fops =
{
fifo_open, /* open */
fifo_close, /* close */
fifo_read, /* read */
fifo_write, /* write */
0, /* seek */
0 /* ioctl */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: fifo_allocdev
****************************************************************************/
static inline FAR struct fifo_dev_s *fifo_allocdev(void)
{
struct fifo_dev_s *dev;
/* Allocate a private structure to manage the FIFO */
dev = (struct fifo_dev_s *)malloc(sizeof(struct fifo_dev_s));
if (dev)
{
/* Initialize the private structure */
sem_init(&dev->d_bfsem, 0, 1);
sem_init(&dev->d_rdsem, 0, 0);
sem_init(&dev->d_wrsem, 0, 0);
dev->d_wrndx = 0;
dev->d_rdndx = 0;
dev->d_refs = 0;
dev->d_nreaders = 0;
dev->d_nwriters = 0;
}
return dev;
}
/****************************************************************************
* Name: fifo_freedev
****************************************************************************/
static inline void fifo_freedev(FAR struct fifo_dev_s *dev)
{
sem_destroy(&dev->d_bfsem);
sem_destroy(&dev->d_rdsem);
sem_destroy(&dev->d_wrsem);
free(dev);
}
/****************************************************************************
* Name: fifo_semtake
****************************************************************************/
static void fifo_semtake(sem_t *sem)
{
while (sem_wait(sem) != 0)
{
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
ASSERT(errno == EINTR);
}
}
/****************************************************************************
* Name: fifo_open
****************************************************************************/
static int fifo_open(FAR struct file *filep)
{
struct inode *inode = filep->f_inode;
struct fifo_dev_s *dev = inode->i_private;
/* The device structure will be allocated the first time that the FIFO is
* opened
*/
if (!dev)
{
/* Allocate and initialize a new device structure instance */
dev = fifo_allocdev();
if (!dev)
{
return -ENOMEM;
}
/* Set the private data on the inode to this instance */
inode->i_private = dev;
}
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->d_bfsem) == 0)
{
/* Increment the reference count on the fifo instance */
dev->d_refs++;
(void)sem_post(&dev->d_bfsem);
return OK;
}
return ERROR;
}
/****************************************************************************
* Name: fifo_close
****************************************************************************/
static int fifo_close(FAR struct file *filep)
{
struct inode *inode = filep->f_inode;
struct fifo_dev_s *dev = inode->i_private;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -EBADF;
}
#endif
/* Make sure that we have exclusive access to the device structure.
* NOTE: close() is supposed to return EINTR if interrupted, however
* I've never seen anyone check that.
*/
fifo_semtake(&dev->d_bfsem);
/* Check if the decremented reference count would be zero */
if (dev->d_refs > 1)
{
/* No.. then just decrement the reference count */
dev->d_refs--;
sem_post(&dev->d_bfsem);
}
else
{
/* Then nothing else can be holding the semaphore, so it is save to */
inode->i_private = NULL;
sem_post(&dev->d_bfsem);
/* Then free the fifo structure instance */
fifo_freedev(dev);
}
return OK;
}
/****************************************************************************
* Name: fifo_read
****************************************************************************/
static ssize_t fifo_read(FAR struct file *filep, FAR char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct fifo_dev_s *dev = inode->i_private;
ssize_t nread = 0;
int ret;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -ENODEV;
}
#endif
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->d_bfsem) < 0)
{
return ERROR;
}
/* If the fifo is empty, then wait for something to be written to it */
while (dev->d_wrndx == dev->d_rdndx)
{
/* If O_NONBLOCK was set, then return EGAIN */
if (filep->f_oflags & O_NONBLOCK)
{
sem_post(&dev->d_bfsem);
return -EAGAIN;
}
/* Otherwise, wait for something to be written to the FIFO */
dev->d_nreaders++;
sched_lock();
sem_post(&dev->d_bfsem);
ret = sem_wait(&dev->d_rdsem);
sched_unlock();
if (ret < 0 || sem_wait(&dev->d_bfsem) < 0)
{
return ERROR;
}
}
/* Then return whatever is available in the FIFO (which is at least one byte) */
nread = 0;
while (nread < len && dev->d_wrndx != dev->d_rdndx)
{
*buffer++ = dev->d_buffer[dev->d_rdndx];
if (++dev->d_rdndx >= CONFIG_DEV_FIFO_SIZE)
{
dev->d_rdndx = 0;
}
nread++;
}
/* Notify any waiting writers that bytes have been removed from the buffer */
if (dev->d_nwriters > 0)
{
dev->d_nwriters--;
sem_post(&dev->d_wrsem);
}
sem_post(&dev->d_bfsem);
return nread;
}
/****************************************************************************
* Name: fifo_write
****************************************************************************/
static ssize_t fifo_write(FAR struct file *filep, FAR const char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct fifo_dev_s *dev = inode->i_private;
ssize_t nwritten = 0;
ssize_t last;
int nxtwrndx;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -ENODEV;
}
#endif
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->d_bfsem) < 0)
{
return ERROR;
}
/* Loop until all of the bytes have been written */
last = 0;
for (;;)
{
/* Calculate the write index AFTER the next byte is written */
nxtwrndx = dev->d_wrndx + 1;
if (nxtwrndx >= CONFIG_DEV_FIFO_SIZE)
{
nxtwrndx = 0;
}
/* Would the next write overflow the circular buffer? */
if (nxtwrndx != dev->d_rdndx)
{
/* No... copy the byte */
dev->d_buffer[dev->d_wrndx] = *buffer++;
dev->d_wrndx = nxtwrndx;
/* Is the write complete? */
if (++nwritten >= len)
{
/* Yes.. Notify the waiting readers that more data is available */
if (dev->d_nreaders > 0)
{
dev->d_nreaders--;
sem_post(&dev->d_rdsem);
}
/* Return the number of bytes written */
sem_post(&dev->d_bfsem);
return len;
}
}
else
{
/* There is not enough room for the next byte. Was anything written in this pass? */
if (last < nwritten)
{
/* Yes.. Notify the waiting readers that more data is available */
if (dev->d_nreaders > 0)
{
dev->d_nreaders--;
sem_post(&dev->d_rdsem);
}
}
last = nwritten;
/* If O_NONBLOCK was set, then return partial bytes written or EGAIN */
if (filep->f_oflags & O_NONBLOCK)
{
if (nwritten == 0)
{
nwritten = -EAGAIN;
}
sem_post(&dev->d_bfsem);
return nwritten;
}
/* There is more to be written.. wait for data to be removed from the FIFO */
dev->d_nwriters++;
sched_lock();
sem_post(&dev->d_bfsem);
fifo_semtake(&dev->d_wrsem);
sched_unlock();
fifo_semtake(&dev->d_bfsem);
}
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: mkfifo
*
* Description:
* 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 mkfifo(), any thread can open it for
* reading or writing, in the same way as an ordinary file. NuttX FIFOs need
* not be open at both ends before input or output operations on it.
*
* Inputs:
* pathname - The full path to the FIFO instance to attach to or to create
* (if not already created).
* mode - Ignored for now
*
* Return:
* 0 is returned on success; otherwise, -1 is returned with errno set
* appropriately.
*
****************************************************************************/
int mkfifo(FAR const char *pathname, mode_t mode)
{
return register_driver(pathname, &fifo_fops, mode, NULL);
}
#endif
