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nuttx/fs/vfs/fs_poll.c

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/****************************************************************************
* fs/vfs/fs_poll.c
*
* Copyright (C) 2008-2009, 2012-2014 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <stdbool.h>
#include <poll.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/sched.h>
#include <nuttx/clock.h>
#include <nuttx/fs/fs.h>
#include <arch/irq.h>
#include "inode/inode.h"
#ifndef CONFIG_DISABLE_POLL
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define poll_semgive(sem) sem_post(sem)
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: poll_semtake
****************************************************************************/
static int poll_semtake(FAR sem_t *sem)
{
/* Take the semaphore (perhaps waiting) */
if (sem_wait(sem) < 0)
{
int err = get_errno();
/* The only case that an error should occur here is if the wait were
* awakened by a signal.
*/
DEBUGASSERT(err == EINTR);
return -err;
}
return OK;
}
/****************************************************************************
* Name: poll_fdsetup
*
* Description:
* Configure (or unconfigure) one file/socket descriptor for the poll
* operation. If fds and sem are non-null, then the poll is being setup.
* if fds and sem are NULL, then the poll is being torn down.
*
****************************************************************************/
#if CONFIG_NFILE_DESCRIPTORS > 0
static int poll_fdsetup(int fd, FAR struct pollfd *fds, bool setup)
{
FAR struct file *filep;
FAR struct inode *inode;
int ret = -ENOSYS;
/* Check for a valid file descriptor */
if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
{
/* Perform the socket ioctl */
#if defined(CONFIG_NET) && CONFIG_NSOCKET_DESCRIPTORS > 0
if ((unsigned int)fd < (CONFIG_NFILE_DESCRIPTORS+CONFIG_NSOCKET_DESCRIPTORS))
{
return net_poll(fd, fds, setup);
}
else
#endif
{
return -EBADF;
}
}
/* Get the file pointer corresponding to this file descriptor */
filep = fs_getfilep(fd);
if (!filep)
{
/* The errno value has already been set */
return ERROR;
}
/* Is a driver registered? Does it support the poll method?
* If not, return -ENOSYS
*/
inode = filep->f_inode;
if (inode && inode->u.i_ops && inode->u.i_ops->poll)
{
/* Yes, then setup the poll */
ret = (int)inode->u.i_ops->poll(filep, fds, setup);
}
return ret;
}
#endif
/****************************************************************************
* Name: poll_setup
*
* Description:
* Setup the poll operation for each descriptor in the list.
*
****************************************************************************/
#if CONFIG_NFILE_DESCRIPTORS > 0
static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds, sem_t *sem)
{
unsigned int i;
int ret;
/* Process each descriptor in the list */
for (i = 0; i < nfds; i++)
{
/* Setup the poll descriptor */
fds[i].sem = sem;
fds[i].revents = 0;
fds[i].priv = NULL;
/* Check for invalid descriptors. "If the value of fd is less than 0,
* events shall be ignored, and revents shall be set to 0 in that entry
* on return from poll()."
*
* NOTE: There is a potential problem here. If there is only one fd
* and if it is negative, then poll will hang. From my reading of the
* spec, that appears to be the correct behavior.
*/
if (fds[i].fd >= 0)
{
/* Set up the poll on this valid file descriptor */
ret = poll_fdsetup(fds[i].fd, &fds[i], true);
if (ret < 0)
{
return ret;
}
}
}
return OK;
}
#endif
/****************************************************************************
* Name: poll_teardown
*
* Description:
* Teardown the poll operation for each descriptor in the list and return
* the count of non-zero poll events.
*
****************************************************************************/
#if CONFIG_NFILE_DESCRIPTORS > 0
static inline int poll_teardown(FAR struct pollfd *fds, nfds_t nfds, int *count,
int ret)
{
unsigned int i;
int status;
/* Process each descriptor in the list */
*count = 0;
for (i = 0; i < nfds; i++)
{
/* Ignore negative descriptors */
if (fds[i].fd >= 0)
{
/* Teardown the poll */
status = poll_fdsetup(fds[i].fd, &fds[i], false);
if (status < 0)
{
ret = status;
}
}
/* Check if any events were posted */
if (fds[i].revents != 0)
{
(*count)++;
}
/* Un-initialize the poll structure */
fds[i].sem = NULL;
}
return ret;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: poll
*
* Description:
* poll() waits for one of a set of file descriptors to become ready to
* perform I/O. If none of the events requested (and no error) has
* occurred for any of the file descriptors, then poll() blocks until
* one of the events occurs.
*
* Inputs:
* fds - List of structures describing file descriptors to be monitored
* nfds - The number of entries in the list
* timeout - Specifies an upper limit on the time for which poll() will
* block in milliseconds. A negative value of timeout means an infinite
* timeout.
*
* Return:
* On success, the number of structures that have non-zero revents fields.
* A value of 0 indicates that the call timed out and no file descriptors
* were ready. On error, -1 is returned, and errno is set appropriately:
*
* EBADF - An invalid file descriptor was given in one of the sets.
* EFAULT - The fds address is invalid
* EINTR - A signal occurred before any requested event.
* EINVAL - The nfds value exceeds a system limit.
* ENOMEM - There was no space to allocate internal data structures.
* ENOSYS - One or more of the drivers supporting the file descriptor
* does not support the poll method.
*
****************************************************************************/
int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
{
struct timespec abstime;
irqstate_t flags;
sem_t sem;
int count = 0;
int ret;
sem_init(&sem, 0, 0);
ret = poll_setup(fds, nfds, &sem);
if (ret >= 0)
{
if (timeout == 0)
{
/* Poll returns immediately whether we have a poll event or not. */
ret = OK;
}
else if (timeout > 0)
{
time_t sec;
uint32_t nsec;
/* Either wait for either a poll event(s), for a signal to occur,
* or for the specified timeout to elapse with no event.
*
* NOTE: If a poll event is pending (i.e., the semaphore has already
* been incremented), sem_timedwait() will not wait, but will return
* immediately.
*/
sec = timeout / MSEC_PER_SEC;
nsec = (timeout - MSEC_PER_SEC * sec) * NSEC_PER_MSEC;
/* Make sure that the following are atomic by disabling interrupts.
* Interrupts will be re-enabled while we are waiting.
*/
flags = irqsave();
(void)clock_gettime(CLOCK_REALTIME, &abstime);
abstime.tv_sec += sec;
abstime.tv_nsec += nsec;
if (abstime.tv_nsec > NSEC_PER_SEC)
{
abstime.tv_sec++;
abstime.tv_nsec -= NSEC_PER_SEC;
}
ret = sem_timedwait(&sem, &abstime);
if (ret < 0)
{
int err = get_errno();
if (err == ETIMEDOUT)
{
/* Return zero (OK) in the event of a timeout */
ret = OK;
}
else
{
ret = -err;
}
}
irqrestore(flags);
}
else
{
/* Wait for the poll event or signal with no timeout */
ret = poll_semtake(&sem);
}
/* Teardown the poll operation and get the count of events. Zero will be
* returned in the case of a timeout.
*/
ret = poll_teardown(fds, nfds, &count, ret);
}
sem_destroy(&sem);
/* Check for errors */
if (ret < 0)
{
set_errno(-ret);
return ERROR;
}
return count;
}
#endif /* CONFIG_DISABLE_POLL */
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