nuttx/drivers/misc/dev_zero.c

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/****************************************************************************
* drivers/misc/dev_zero.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 <nuttx/config.h>
#include <sys/types.h>
#include <stdbool.h>
#include <string.h>
#include <poll.h>
#include <errno.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include <nuttx/drivers/drivers.h>
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static ssize_t devzero_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t devzero_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static int devzero_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations devzero_fops =
{
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NULL, /* open */
NULL, /* close */
devzero_read, /* read */
devzero_write, /* write */
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NULL, /* seek */
NULL, /* ioctl */
NULL, /* truncate */
devzero_poll /* poll */
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#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, NULL /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: devzero_read
****************************************************************************/
static ssize_t devzero_read(FAR struct file *filep, FAR char *buffer,
size_t len)
{
UNUSED(filep);
memset(buffer, 0, len);
return len;
}
/****************************************************************************
* Name: devzero_write
****************************************************************************/
static ssize_t devzero_write(FAR struct file *filep, FAR const char *buffer,
size_t len)
{
UNUSED(filep);
UNUSED(buffer);
return len;
}
/****************************************************************************
* Name: devzero_poll
****************************************************************************/
static int devzero_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup)
{
UNUSED(filep);
if (setup)
{
poll_notify(&fds, 1, POLLIN | POLLOUT);
}
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: devzero_register
*
* Description:
* Register /dev/zero
*
****************************************************************************/
void devzero_register(void)
{
register_driver("/dev/zero", &devzero_fops, 0666, NULL);
}