forked from Archive/PX4-Autopilot
128 lines
4.5 KiB
C
128 lines
4.5 KiB
C
/****************************************************************************
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* drivers/dev_null.c
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*
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* Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdbool.h>
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#include <string.h>
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#include <poll.h>
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#include <errno.h>
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#include <nuttx/fs/fs.h>
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static ssize_t devzero_read(FAR struct file *, FAR char *, size_t);
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static ssize_t devzero_write(FAR struct file *, FAR const char *, size_t);
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#ifndef CONFIG_DISABLE_POLL
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static int devzero_poll(FAR struct file *filp, FAR struct pollfd *fds,
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bool setup);
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#endif
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations devzero_fops =
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{
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0, /* open */
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0, /* close */
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devzero_read, /* read */
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devzero_write, /* write */
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0, /* seek */
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0 /* ioctl */
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#ifndef CONFIG_DISABLE_POLL
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, devzero_poll /* poll */
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#endif
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: devzero_read
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****************************************************************************/
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static ssize_t devzero_read(FAR struct file *filp, FAR char *buffer, size_t len)
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{
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memset(buffer, 0, len);
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return len;
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}
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/****************************************************************************
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* Name: devzero_write
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****************************************************************************/
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static ssize_t devzero_write(FAR struct file *filp, FAR const char *buffer, size_t len)
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{
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return len;
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}
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/****************************************************************************
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* Name: devzero_poll
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****************************************************************************/
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#ifndef CONFIG_DISABLE_POLL
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static int devzero_poll(FAR struct file *filp, FAR struct pollfd *fds,
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bool setup)
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{
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if (setup)
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{
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fds->revents |= (fds->events & (POLLIN|POLLOUT));
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if (fds->revents != 0)
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{
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sem_post(fds->sem);
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}
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}
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return OK;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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void devzero_register(void)
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{
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(void)register_driver("/dev/zero", &devzero_fops, 0666, NULL);
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}
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