From 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 12:05:51 +0200 Subject: Adding upstream version 5.10.209. Signed-off-by: Daniel Baumann --- drivers/tty/n_tracesink.c | 230 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 230 insertions(+) create mode 100644 drivers/tty/n_tracesink.c (limited to 'drivers/tty/n_tracesink.c') diff --git a/drivers/tty/n_tracesink.c b/drivers/tty/n_tracesink.c new file mode 100644 index 000000000..1d9931041 --- /dev/null +++ b/drivers/tty/n_tracesink.c @@ -0,0 +1,230 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * n_tracesink.c - Trace data router and sink path through tty space. + * + * Copyright (C) Intel 2011 + * + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * + * The trace sink uses the Linux line discipline framework to receive + * trace data coming from the PTI source line discipline driver + * to a user-desired tty port, like USB. + * This is to provide a way to extract modem trace data on + * devices that do not have a PTI HW module, or just need modem + * trace data to come out of a different HW output port. + * This is part of a solution for the P1149.7, compact JTAG, standard. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#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_tracesink" + +/* + * there is a quirk with this ldisc is he can write data + * to a tty from anyone calling his kernel API, which + * meets customer requirements in the drivers/misc/pti.c + * project. So he needs to know when he can and cannot write when + * the API is called. In theory, the API can be called + * after an init() but before a successful open() which + * would crash the system if tty is not checked. + */ +static struct tty_struct *this_tty; +static DEFINE_MUTEX(writelock); + +/** + * n_tracesink_open() - Called when a tty is opened by a SW entity. + * @tty: terminal device to the ldisc. + * + * Return: + * 0 for success, + * -EFAULT = couldn't get a tty kref n_tracesink will sit + * on top of + * -EEXIST = open() called successfully once and it cannot + * be called again. + * + * Caveats: open() should only be successful the first time a + * SW entity calls it. + */ +static int n_tracesink_open(struct tty_struct *tty) +{ + int retval = -EEXIST; + + mutex_lock(&writelock); + if (this_tty == NULL) { + this_tty = tty_kref_get(tty); + if (this_tty == NULL) { + retval = -EFAULT; + } else { + tty->disc_data = this_tty; + tty_driver_flush_buffer(tty); + retval = 0; + } + } + mutex_unlock(&writelock); + + return retval; +} + +/** + * n_tracesink_close() - close connection + * @tty: terminal device to the ldisc. + * + * Called when a software entity wants to close a connection. + */ +static void n_tracesink_close(struct tty_struct *tty) +{ + mutex_lock(&writelock); + tty_driver_flush_buffer(tty); + tty_kref_put(this_tty); + this_tty = NULL; + tty->disc_data = NULL; + mutex_unlock(&writelock); +} + +/** + * n_tracesink_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_tracesink_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_tracesink_read(struct tty_struct *tty, struct file *file, + unsigned char *buf, size_t nr, + void **cookie, unsigned long offset) +{ + return -EINVAL; +} + +/** + * n_tracesink_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_tracesink_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_tracesink_write(struct tty_struct *tty, struct file *file, + const unsigned char *buf, size_t nr) { + return -EINVAL; +} + +/** + * n_tracesink_datadrain() - Kernel API function used to route + * trace debugging data to user-defined + * port like USB. + * + * @buf: Trace debuging data buffer to write to tty target + * port. Null value will return with no write occurring. + * @count: Size of buf. Value of 0 or a negative number will + * return with no write occuring. + * + * Caveat: If this line discipline does not set the tty it sits + * on top of via an open() call, this API function will not + * call the tty's write() call because it will have no pointer + * to call the write(). + */ +void n_tracesink_datadrain(u8 *buf, int count) +{ + mutex_lock(&writelock); + + if ((buf != NULL) && (count > 0) && (this_tty != NULL)) + this_tty->ops->write(this_tty, buf, count); + + mutex_unlock(&writelock); +} +EXPORT_SYMBOL_GPL(n_tracesink_datadrain); + +/* + * 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. + */ + +/* + * tty_ldisc function operations for this driver. + */ +static struct tty_ldisc_ops tty_n_tracesink = { + .owner = THIS_MODULE, + .magic = TTY_LDISC_MAGIC, + .name = DRIVERNAME, + .open = n_tracesink_open, + .close = n_tracesink_close, + .read = n_tracesink_read, + .write = n_tracesink_write +}; + +/** + * n_tracesink_init- module initialisation + * + * Registers this module as a line discipline driver. + * + * Return: + * 0 for success, any other value error. + */ +static int __init n_tracesink_init(void) +{ + /* Note N_TRACESINK is defined in linux/tty.h */ + int retval = tty_register_ldisc(N_TRACESINK, &tty_n_tracesink); + + if (retval < 0) + pr_err("%s: Registration failed: %d\n", __func__, retval); + + return retval; +} + +/** + * n_tracesink_exit - module unload + * + * Removes this module as a line discipline driver. + */ +static void __exit n_tracesink_exit(void) +{ + int retval = tty_unregister_ldisc(N_TRACESINK); + + if (retval < 0) + pr_err("%s: Unregistration failed: %d\n", __func__, retval); +} + +module_init(n_tracesink_init); +module_exit(n_tracesink_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Jay Freyensee"); +MODULE_ALIAS_LDISC(N_TRACESINK); +MODULE_DESCRIPTION("Trace sink ldisc driver"); -- cgit v1.2.3