lkml.org 
[lkml]   [2011]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 10/12] n_tracerouter ldisc driver.
    Date
    From: J Freyensee <james_p_freyensee@linux.intel.com>

    This patch adds the n_tracerouter ldisc driver. It is part
    of the Intel-Atom PTI implementation solution.

    Signed-off-by: J Freyensee <james_p_freyensee@linux.intel.com>
    ---
    drivers/tty/n_tracerouter.c | 264 +++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 264 insertions(+), 0 deletions(-)
    create mode 100644 drivers/tty/n_tracerouter.c

    diff --git a/drivers/tty/n_tracerouter.c b/drivers/tty/n_tracerouter.c
    new file mode 100644
    index 0000000..1bb8c9e
    --- /dev/null
    +++ b/drivers/tty/n_tracerouter.c
    @@ -0,0 +1,264 @@
    +/*
    + * n_tracerouter.c - Trace data router through tty space
    + *
    + * Copyright (C) Intel 2010
    + *
    + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + *
    + * 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.
    + *
    + * You should have received a copy of the GNU General Public License
    + * along with this program; if not, write to the Free Software
    + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    + * 02110-1301, USA
    + *
    + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + *
    + * 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 <linux/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 ioctl() setting of tracerouter_data values */
    +static DEFINE_MUTEX(routelock);
    +
    +/**
    + * tracerouter_alloc
    + *
    + * Allocates the structure needed for this ldisc.
    + */
    +static struct tracerouter_data *tracerouter_alloc(void)
    +{
    + struct tracerouter_data *tptr = kzalloc(
    + sizeof(struct tracerouter_data),
    + GFP_KERNEL);
    + if (tptr == NULL)
    + return NULL;
    + tptr->opencalled = 0;
    + return tptr;
    +}
    +
    +/**
    + * 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;
    +
    + WARN_ON(tptr->kref_tty != tr_data->kref_tty);
    + tty_driver_flush_buffer(tty);
    + mutex_lock(&routelock);
    + 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 = tracerouter_alloc();
    + 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;
    +
    + kfree(tr_data);
    + retval = tty_unregister_ldisc(N_TRACEROUTER);
    + if (retval < 0)
    + pr_err("%s: Unregistration failed: %d\n",
    + __func__, retval);
    +}
    +
    +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");
    --
    1.6.6.1


    \
     
     \ /
      Last update: 2011-02-08 20:39    [W:0.033 / U:2.584 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site