331 lines
9.2 KiB
C
331 lines
9.2 KiB
C
/****************************************************************************
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* drivers/serial/ptmx.c
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*
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* Copyright (C) 2016 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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#ifndef CONFIG_PTY_MAXPTY
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# define CONFIG_PTY_MAXPTY 32
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#endif
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#if CONFIG_PTY_MAXPTY > 256
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# define CONFIG_PTY_MAXPTY 256
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#endif
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#define PTY_MAX ((CONFIG_PTY_MAXPTY + 31) & ~31)
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#define INDEX_MAX (PTY_MAX >> 5)
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/****************************************************************************
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* Private Types
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****************************************************************************/
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/* PTMX device state */
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struct ptmx_dev_s
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{
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uint8_t px_next; /* Next minor number to allocate */
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sem_t px_exclsem; /* Supports mutual exclusion */
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uint32_t px_alloctab[INDEX_MAX]; /* Set of allocated PTYs */
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static int ptmx_open(FAR struct file *filep);
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static ssize_t ptmx_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen);
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static ssize_t ptmx_write(FAR struct file *filep, FAR const char *buffer,
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size_t buflen);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_ptmx_fops =
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{
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ptmx_open, /* open */
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NULL, /* close */
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ptmx_read, /* read */
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ptmx_write, /* write */
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NULL, /* seek */
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NULL /* ioctl */
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#ifndef CONFIG_DISABLE_POLL
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, NULL /* poll */
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#endif
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#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
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, NULL /* unlink */
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#endif
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};
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static struct ptmx_dev_s g_ptmx;
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: ptmx_semtake and ptmx_semgive
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*
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* Description:
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* This is just a wrapper to handle the annoying behavior of semaphore
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* waits that return due to the receipt of a signal.
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*
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****************************************************************************/
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static void ptmx_semtake(void)
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{
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/* Take the semaphore (perhaps waiting) */
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while (sem_wait(&g_ptmx.px_exclsem) != 0)
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{
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/* The only case that an error should occur here is if the wait was
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* awakened by a signal.
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*/
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DEBUGASSERT(errno == EINTR);
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}
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}
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#define ptmx_semgive() sem_post(&g_ptmx.px_exclsem)
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/****************************************************************************
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* Name: ptmx_minor_allocate
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*
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* Description:
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* Allocate a new unique PTY minor number.
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*
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* Assumptions:
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* Caller hold the px_exclsem
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*
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****************************************************************************/
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static int ptmx_minor_allocate(FAR struct ptmx_dev_s *ptmx)
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{
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uint8_t startaddr = g_ptmx.px_next;
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uint8_t minor;
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int index;
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int bitno;
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/* Loop until we find a valid device address */
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for (; ; )
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{
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/* Try the next device address */
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minor = g_ptmx.px_next;
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if (g_ptmx.px_next >= PTY_MAX)
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{
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g_ptmx.px_next = 0;
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}
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else
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{
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g_ptmx.px_next++;
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}
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/* Is this address already allocated? */
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index = minor >> 5;
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bitno = minor & 31;
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if ((g_ptmx.px_alloctab[index] & (1 << bitno)) == 0)
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{
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/* No... allocate it now */
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g_ptmx.px_alloctab[index] |= (1 << bitno);
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return (int)minor;
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}
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/* This address has already been allocated. The following logic will
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* prevent (unexpected) infinite loops.
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*/
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if (startaddr == minor)
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{
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/* We are back where we started... the are no free device address */
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return -ENOMEM;
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}
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}
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}
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/****************************************************************************
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* Name: ptmx_minor_free
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*
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* Description:
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* De-allocate a PTY minor number.
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*
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* Assumptions:
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* Caller hold the px_exclsem
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*
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****************************************************************************/
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static void ptmx_minor_free(uint8_t minor)
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{
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int index;
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int bitno;
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/* Free the address by clearing the associated bit in the px_alloctab[]; */
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index = minor >> 5;
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bitno = minor & 31;
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DEBUGASSERT((g_ptmx.px_alloctab[index] |= (1 << bitno)) != 0);
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g_ptmx.px_alloctab[index] &= ~(1 << bitno);
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/* Reset the next pointer if the one just released has a lower value */
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if (minor < g_ptmx.px_next)
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{
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g_ptmx.px_next = minor;
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}
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}
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/****************************************************************************
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* Name: ptmx_open
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****************************************************************************/
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static int ptmx_open(FAR struct file *filep)
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{
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char devname[16];
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int minor;
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int fd;
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int ret;
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/* Get exclusive access */
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ptmx_semtake();
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/* Allocate a PTY minor */
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minor = ptmx_minor_allocate();
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if (minor < 0)
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{
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ret = minor;
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goto errout_with_sem;
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}
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/* Create the master slave pair */
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ret = pty_register(minor);
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if (ret < 0)
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{
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goto errout_with_minor;
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}
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/* Open the master side */
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snprintf(devname, 16, "/dev/ttyp%d", minor);
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fd = open(devname, O_RDWR);
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DEBUGASSERT(fd >= 0); /* open() should never fail */
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/* No unlink the master. This will remove it from the VFS namespace,
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* the the driver will still persist because of the open count on the
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* driver.
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*/
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ret = unlink(devname);
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DEBUGASSERT(ret >= 0); /* unlink() should never fail */
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UNUSED(ret);
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/* Return the master file descriptor */
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ptmx_semgive();
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return fd;
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errout_with_minor:
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ptmx_minor_free(minor);
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errout_with_sem:
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ptmx_semgive();
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return ret;
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}
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/****************************************************************************
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* Name: ptmx_read
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****************************************************************************/
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static ssize_t ptmx_read(FAR struct file *filep, FAR char *buffer, size_t len)
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{
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return 0; /* Return EOF */
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}
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/****************************************************************************
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* Name: ptmx_write
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****************************************************************************/
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static ssize_t ptmx_write(FAR struct file *filep, FAR const char *buffer, size_t len)
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{
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return len; /* Say that everything was written */
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: ptmx_register
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*
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* Description:
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* Register /dev/null
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*
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****************************************************************************/
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void ptmx_register(void)
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{
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FAR struct ptmx_dev_s *ptmx;
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/* Initialize driver state */
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sem_init(&g_ptmx.px_exclsem, 0, 1);
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/* Register the PTMX driver */
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(void)register_driver("/dev/ptmx", &g_ptmx_fops, 0666, NULL);
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}
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