244 lines
7.1 KiB
C
244 lines
7.1 KiB
C
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/*
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* n_tracerouter.c - Trace data router through tty space
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*
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* Copyright (C) Intel 2011
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*
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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*
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* This trace router uses the Linux line discipline framework to route
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* trace data coming from a HW Modem to a PTI (Parallel Trace Module) port.
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* The solution is not specific to a HW modem and this line disciple can
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* be used to route any stream of data in kernel space.
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* This is part of a solution for the P1149.7, compact JTAG, standard.
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/ioctl.h>
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#include <linux/tty.h>
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#include <linux/tty_ldisc.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/bug.h>
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#include "n_tracesink.h"
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/*
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* Other ldisc drivers use 65536 which basically means,
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* 'I can always accept 64k' and flow control is off.
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* This number is deemed appropriate for this driver.
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*/
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#define RECEIVE_ROOM 65536
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#define DRIVERNAME "n_tracerouter"
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/*
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* struct to hold private configuration data for this ldisc.
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* opencalled is used to hold if this ldisc has been opened.
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* kref_tty holds the tty reference the ldisc sits on top of.
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*/
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struct tracerouter_data {
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u8 opencalled;
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struct tty_struct *kref_tty;
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};
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static struct tracerouter_data *tr_data;
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/* lock for when tty reference is being used */
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static DEFINE_MUTEX(routelock);
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/**
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* n_tracerouter_open() - Called when a tty is opened by a SW entity.
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* @tty: terminal device to the ldisc.
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*
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* Return:
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* 0 for success.
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*
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* Caveats: This should only be opened one time per SW entity.
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*/
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static int n_tracerouter_open(struct tty_struct *tty)
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{
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int retval = -EEXIST;
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mutex_lock(&routelock);
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if (tr_data->opencalled == 0) {
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tr_data->kref_tty = tty_kref_get(tty);
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if (tr_data->kref_tty == NULL) {
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retval = -EFAULT;
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} else {
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tr_data->opencalled = 1;
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tty->disc_data = tr_data;
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tty->receive_room = RECEIVE_ROOM;
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tty_driver_flush_buffer(tty);
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retval = 0;
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}
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}
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mutex_unlock(&routelock);
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return retval;
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}
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/**
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* n_tracerouter_close() - close connection
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* @tty: terminal device to the ldisc.
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*
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* Called when a software entity wants to close a connection.
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*/
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static void n_tracerouter_close(struct tty_struct *tty)
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{
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struct tracerouter_data *tptr = tty->disc_data;
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mutex_lock(&routelock);
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WARN_ON(tptr->kref_tty != tr_data->kref_tty);
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tty_driver_flush_buffer(tty);
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tty_kref_put(tr_data->kref_tty);
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tr_data->kref_tty = NULL;
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tr_data->opencalled = 0;
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tty->disc_data = NULL;
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mutex_unlock(&routelock);
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}
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/**
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* n_tracerouter_read() - read request from user space
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* @tty: terminal device passed into the ldisc.
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* @file: pointer to open file object.
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* @buf: pointer to the data buffer that gets eventually returned.
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* @nr: number of bytes of the data buffer that is returned.
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*
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* function that allows read() functionality in userspace. By default if this
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* is not implemented it returns -EIO. This module is functioning like a
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* router via n_tracerouter_receivebuf(), and there is no real requirement
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* to implement this function. However, an error return value other than
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* -EIO should be used just to show that there was an intent not to have
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* this function implemented. Return value based on read() man pages.
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*
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* Return:
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* -EINVAL
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*/
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static ssize_t n_tracerouter_read(struct tty_struct *tty, struct file *file,
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unsigned char __user *buf, size_t nr) {
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return -EINVAL;
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}
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/**
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* n_tracerouter_write() - Function that allows write() in userspace.
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* @tty: terminal device passed into the ldisc.
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* @file: pointer to open file object.
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* @buf: pointer to the data buffer that gets eventually returned.
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* @nr: number of bytes of the data buffer that is returned.
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*
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* By default if this is not implemented, it returns -EIO.
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* This should not be implemented, ever, because
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* 1. this driver is functioning like a router via
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* n_tracerouter_receivebuf()
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* 2. No writes to HW will ever go through this line discpline driver.
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* However, an error return value other than -EIO should be used
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* just to show that there was an intent not to have this function
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* implemented. Return value based on write() man pages.
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*
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* Return:
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* -EINVAL
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*/
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static ssize_t n_tracerouter_write(struct tty_struct *tty, struct file *file,
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const unsigned char *buf, size_t nr) {
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return -EINVAL;
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}
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/**
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* n_tracerouter_receivebuf() - Routing function for driver.
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* @tty: terminal device passed into the ldisc. It's assumed
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* tty will never be NULL.
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* @cp: buffer, block of characters to be eventually read by
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* someone, somewhere (user read() call or some kernel function).
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* @fp: flag buffer.
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* @count: number of characters (aka, bytes) in cp.
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*
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* This function takes the input buffer, cp, and passes it to
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* an external API function for processing.
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*/
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static void n_tracerouter_receivebuf(struct tty_struct *tty,
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const unsigned char *cp,
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char *fp, int count)
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{
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mutex_lock(&routelock);
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n_tracesink_datadrain((u8 *) cp, count);
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mutex_unlock(&routelock);
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}
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/*
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* Flush buffer is not impelemented as the ldisc has no internal buffering
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* so the tty_driver_flush_buffer() is sufficient for this driver's needs.
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*/
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static struct tty_ldisc_ops tty_ptirouter_ldisc = {
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.owner = THIS_MODULE,
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.magic = TTY_LDISC_MAGIC,
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.name = DRIVERNAME,
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.open = n_tracerouter_open,
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.close = n_tracerouter_close,
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.read = n_tracerouter_read,
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.write = n_tracerouter_write,
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.receive_buf = n_tracerouter_receivebuf
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};
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/**
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* n_tracerouter_init - module initialisation
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*
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* Registers this module as a line discipline driver.
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*
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* Return:
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* 0 for success, any other value error.
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*/
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static int __init n_tracerouter_init(void)
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{
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int retval;
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tr_data = kzalloc(sizeof(struct tracerouter_data), GFP_KERNEL);
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if (tr_data == NULL)
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return -ENOMEM;
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/* Note N_TRACEROUTER is defined in linux/tty.h */
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retval = tty_register_ldisc(N_TRACEROUTER, &tty_ptirouter_ldisc);
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if (retval < 0) {
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pr_err("%s: Registration failed: %d\n", __func__, retval);
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kfree(tr_data);
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}
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return retval;
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}
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/**
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* n_tracerouter_exit - module unload
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*
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* Removes this module as a line discipline driver.
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*/
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static void __exit n_tracerouter_exit(void)
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{
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int retval = tty_unregister_ldisc(N_TRACEROUTER);
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if (retval < 0)
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pr_err("%s: Unregistration failed: %d\n", __func__, retval);
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else
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kfree(tr_data);
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}
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module_init(n_tracerouter_init);
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module_exit(n_tracerouter_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Jay Freyensee");
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MODULE_ALIAS_LDISC(N_TRACEROUTER);
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MODULE_DESCRIPTION("Trace router ldisc driver");
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