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