--- /dev/null
+/*
+ * 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");
Code Review / kvmfornfv.git / blobdiff