/*
* Industrial Computer Source WDT501 driver
*
* (c) Copyright 1996-1997 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
* warranty for any of this software. This material is provided
* "AS-IS" and at no charge.
*
* (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk>
*
* Release 0.10.
*
* Fixes
* Dave Gregorich : Modularisation and minor bugs
* Alan Cox : Added the watchdog ioctl() stuff
* Alan Cox : Fixed the reboot problem (as noted by
* Matt Crocker).
* Alan Cox : Added wdt= boot option
* Alan Cox : Cleaned up copy/user stuff
* Tim Hockin : Added insmod parameters, comment
* cleanup, parameterized timeout
* Tigran Aivazian : Restructured wdt_init() to handle
* failures
* Joel Becker : Added WDIOC_GET/SETTIMEOUT
* Matt Domsch : Added nowayout module option
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include "wd501p.h"
static unsigned long wdt_is_open;
static char expect_close;
/*
* Module parameters
*/
#define WD_TIMO 60 /* Default heartbeat = 60 seconds */
static int heartbeat = WD_TIMO;
static int wd_heartbeat;
/*
module_param(type, int, 0);//这个代表加载驱动时，可以输入的参数。例如:insmod wdt.ko type=777
module_param(name, type, perm);//第一个参数代表输入参数的名字，第二个代表输入参数的类型，第三个参数表示参数的访问权限，perm表示该参数在sysfs文件系统中所对应的文件节点的属性;你用该使用<linux/stat.h>中定义的权限值;这个值控制谁可以存取这些模块参数在sysfs文件系统中的表示;当perm为0时,表示此参数不存在sysfs文件系统下对应的文件节点;否则,模块被加载后,在/sys/module/目录下将会出现以此模块名命名的目录,带有给定的权限
MODULE_PARM_DESC(tachometer,"WDT501-P Fan Tachometer support (0=disable, default=0)");//表示参数的帮助文档
//使用modinfo hello.ko 可以打印出该驱动的帮助文档
*/
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat,
"Watchdog heartbeat in seconds. (0 < heartbeat < 65536, default="
__MODULE_STRING(WD_TIMO) ")");
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
"Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
/* You must set these - there is no sane way to probe for this board. */
static int io = 0x240;
static int irq = 11;
//用于自旋锁的初始化
static DEFINE_SPINLOCK(wdt_lock);
module_param(io, int, 0);
MODULE_PARM_DESC(io, "WDT io port (default=0x240)");
module_param(irq, int, 0);
MODULE_PARM_DESC(irq, "WDT irq (default=11)");
/* Support for the Fan Tachometer on the WDT501-P */
static int tachometer;
module_param(tachometer, int, 0);
MODULE_PARM_DESC(tachometer,
"WDT501-P Fan Tachometer support (0=disable, default=0)");
static int type = 500;
module_param(type, int, 0);
MODULE_PARM_DESC(type,
"WDT501-P Card type (500 or 501, default=500)");
/*
* Programming support
*/
static void wdt_ctr_mode(int ctr, int mode)
{
ctr <<= 6; //将ctr左移6位
ctr |= 0x30;
ctr |= (mode << 1);
outb_p(ctr, WDT_CR);//将ctr写入wdt_cr寄存器中
}
static void wdt_ctr_load(int ctr, int val)
{
outb_p(val&0xFF, WDT_COUNT0+ctr);
outb_p(val>>8, WDT_COUNT0+ctr);
}
/**
* wdt_start:
*
* Start the watchdog driver.
*/
static int wdt_start(void)
{
unsigned long flags;
//禁止中断的自旋锁
spin_lock_irqsave(&wdt_lock, flags);
inb_p(WDT_DC); /* Disable watchdog */
wdt_ctr_mode(0, 3); /* Program CTR0 for Mode 3:
Square Wave Generator */
wdt_ctr_mode(1, 2); /* Program CTR1 for Mode 2:
Rate Generator */
wdt_ctr_mode(2, 0); /* Program CTR2 for Mode 0:
Pulse on Terminal Count */
wdt_ctr_load(0, 8948); //设置计数频率/* Count at 100Hz */
wdt_ctr_load(1, wd_heartbeat);//设置心跳数
wdt_ctr_load(2, 65535); //设置复位脉冲宽度
outb_p(0, WDT_DC); //往WDT_DC中写入0
spin_unlock_irqrestore(&wdt_lock, flags);
return 0;
}
/**
* wdt_stop:
*
* Stop the watchdog driver.
*/
static int wdt_stop(void)
{
unsigned long flags;
spin_lock_irqsave(&wdt_lock, flags);
/* Turn the card off */
inb_p(WDT_DC); /* Disable watchdog */
wdt_ctr_load(2, 0); /* 0 length reset pulses now */
spin_unlock_irqrestore(&wdt_lock, flags);
return 0;
}
/**
* wdt_ping:
*
* Reload counter one with the watchdog heartbeat. We don't bother
* reloading the cascade counter.
*/
static void wdt_ping(void)
{
unsigned long flags;
spin_lock_irqsave(&wdt_lock, flags);
/* Write a watchdog value */
inb_p(WDT_DC); /* Disable watchdog */
wdt_ctr_mode(1, 2); /* Re-Program CTR1 for Mode 2:
Rate Generator */
wdt_ctr_load(1, wd_heartbeat); /* Heartbeat */ //重新载入超时时间
outb_p(0, WDT_DC); /* Enable watchdog */
spin_unlock_irqrestore(&wdt_lock, flags);
}
/**
* wdt_set_heartbeat:
* @t: 需要被设置的心跳值
*
* 设置新的心跳值，如果该心跳值是不正确的，将会保留默认值，并且返回-EINVAL。
* 成功将返回 0
*/
static int wdt_set_heartbeat(int t)
{
if (t < 1 || t > 65535)
return -EINVAL;
heartbeat = t; //设置两个全局静态变量
wd_heartbeat = t * 100;
return 0;
}
/**
* wdt_get_status:
*
* Extract the status information from a WDT watchdog device. There are
* several board variants so we have to know which bits are valid. Some
* bits default to one and some to zero in order to be maximally painful.
*
* we then map the bits onto the status ioctl flags.
*/
//获取看门狗状态
static int wdt_get_status(void)
{
unsigned char new_status;
int status = 0;
unsigned long flags;
spin_lock_irqsave(&wdt_lock, flags);
new_status = inb_p(WDT_SR);
spin_unlock_irqrestore(&wdt_lock, flags);
if (new_status & WDC_SR_ISOI0)
status |= WDIOF_EXTERN1;
if (new_status & WDC_SR_ISII1)
status |= WDIOF_EXTERN2;
if (type == 501) {
if (!(new_status & WDC_SR_TGOOD))
status |= WDIOF_OVERHEAT;
if (!(new_status & WDC_SR_PSUOVER))
status |= WDIOF_POWEROVER;
if (!(new_status & WDC_SR_PSUUNDR))
status |= WDIOF_POWERUNDER;
if (tachometer) {
if (!(new_status & WDC_SR_FANGOOD))
status |= WDIOF_FANFAULT;
}
}
return status;
}
/**
* wdt_get_temperature:
*
* Reports the temperature in degrees Fahrenheit. The API is in
* farenheit. It was designed by an imperial measurement luddite.
*/
static int wdt_get_temperature(void)
{
unsigned short c;
unsigned long flags;
//禁止中断的自旋锁，将中断的情况保持在flags中
spin_lock_irqsave(&wdt_lock, flags);
c = inb_p(WDT_RT);
//解除自旋锁，并把中断标志还原
spin_unlock_irqrestore(&wdt_lock, flags);
return (c * 11 / 15) + 7;
}
static void wdt_decode_501(int status)
{
if (!(status & WDC_SR_TGOOD))
pr_crit("Overheat alarm (%d)\n", inb_p(WDT_RT));
if (!(status & WDC_SR_PSUOVER))
pr_crit("PSU over voltage\n");
if (!(status & WDC_SR_PSUUNDR))
pr_crit("PSU under voltage\n");
}
/**
* wdt_interrupt:
* @irq: Interrupt number
* @dev_id: Unused as we don't allow multiple devices.
*
* Handle an interrupt from the board. These are raised when the status
* map changes in what the board considers an interesting way. That means
* a failure condition occurring.
*/
/**
* wdt_interrupt: 看门狗的中断处理函数
* @irq: 终端号
* @dev_id: 设备号
*
*/
static irqreturn_t wdt_interrupt(int irq, void *dev_id)
{
/*
* Read the status register see what is up and
* then printk it.
*/
unsigned char status;
//所以在实际编程时，需要注意自旋锁不应该长时间的持有。它适合于短时间的的轻量级的加锁机制
spin_lock(&wdt_lock);//自旋锁开启，处于忙等待状态
status = inb_p(WDT_SR);//暂停式i/o操作函数,即加上_p,而inb表示读取byte类型的地址值
//还有inw,inl,outb,等
pr_crit("WDT status %d\n", status);
if (type == 501) {
wdt_decode_501(status); //打印下看门狗状态
if (tachometer) {
if (!(status & WDC_SR_FANGOOD))
pr_crit("Possible fan fault\n");
}
}
if (!(status & WDC_SR_WCCR)) {
#ifdef SOFTWARE_REBOOT
#ifdef ONLY_TESTING //只是用于测试
pr_crit("Would Reboot\n");
#else
pr_crit("Initiating system reboot\n");
emergency_restart(); //重启设备
#endif
#else
pr_crit("Reset in 5ms\n");
#endif
}
//解除自旋锁
spin_unlock(&wdt_lock);
//表示irq 已经处理过
return IRQ_HANDLED;
}
/**
* wdt_write:
* @file: file handle to the watchdog
* @buf: buffer to write (unused as data does not matter here
* @count: count of bytes
* @ppos: pointer to the position to write. No seeks allowed
*
* A write to a watchdog device is defined as a keepalive signal. Any
* write of data will do, as we we don't define content meaning.
*/
static ssize_t wdt_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
if (count) {
if (!nowayout) {
size_t i;
/* In case it was set long ago */
expect_close = 0;
for (i = 0; i != count; i++) {
char c;
if (get_user(c, buf + i))
return -EFAULT;
if (c == 'V')
expect_close = 42;
}
}
wdt_ping();
}
return count;
}
/**
* wdt_ioctl:
* @file: file handle to the device
* @cmd: watchdog command
* @arg: argument pointer
*
* The watchdog API defines a common set of functions for all watchdogs
* according to their available features. We only actually usefully support
* querying capabilities and current status.
*/
static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
void __user *argp = (void __user *)arg;
int __user *p = argp;
int new_heartbeat;
int status;
struct watchdog_info ident = {
.options = WDIOF_SETTIMEOUT|
WDIOF_MAGICCLOSE|
WDIOF_KEEPALIVEPING,
.firmware_version = 1,
.identity = "WDT500/501",
};
/* Add options according to the card we have */
ident.options |= (WDIOF_EXTERN1|WDIOF_EXTERN2);
if (type == 501) {
ident.options |= (WDIOF_OVERHEAT|WDIOF_POWERUNDER|
WDIOF_POWEROVER);
if (tachometer)
ident.options |= WDIOF_FANFAULT;
}
switch (cmd) {
case WDIOC_GETSUPPORT://把看门狗信息传递给调用者
return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
case WDIOC_GETSTATUS:
status = wdt_get_status();
return put_user(status, p);
case WDIOC_GETBOOTSTATUS:
return put_user(0, p);//把值写到一个用户空间的变量中
case WDIOC_KEEPALIVE:
wdt_ping(); //喂狗
return 0;
case WDIOC_SETTIMEOUT:
if (get_user(new_heartbeat, p))
return -EFAULT;
if (wdt_set_heartbeat(new_heartbeat)) //设置看门狗超时时间
return -EINVAL;
wdt_ping();
/* Fall */
case WDIOC_GETTIMEOUT:
return put_user(heartbeat, p);//获取看门狗超时时间
default:
return -ENOTTY;
}
}
/**
* wdt_open:
* @inode: inode of device
* @file: file handle to device
*
* The watchdog device has been opened. The watchdog device is single
* open and on opening we load the counters. Counter zero is a 100Hz
* cascade, into counter 1 which downcounts to reboot. When the counter
* triggers counter 2 downcounts the length of the reset pulse which
* set set to be as long as possible.
*/
static int wdt_open(struct inode *inode, struct file *file)
{
//将wdt_is_open的第0位设置成1，并返回原来这一位的值
if (test_and_set_bit(0, &wdt_is_open))
return -EBUSY;
/*
* Activate
*/
wdt_start();
return nonseekable_open(inode, file);//打开一个不能seek的文件
}
/**
* wdt_release:
* @inode: inode to board
* @file: file handle to board
*
* The watchdog has a configurable API. There is a religious dispute
* between people who want their watchdog to be able to shut down and
* those who want to be sure if the watchdog manager dies the machine
* reboots. In the former case we disable the counters, in the latter
* case you have to open it again very soon.
*/
static int wdt_release(struct inode *inode, struct file *file)
{
if (expect_close == 42) {
wdt_stop();
clear_bit(0, &wdt_is_open);
} else {
pr_crit("WDT device closed unexpectedly. WDT will not stop!\n");
wdt_ping();
}
expect_close = 0;
return 0;
}
/**
* wdt_temp_read:
* @file: file handle to the watchdog board
* @buf: buffer to write 1 byte into
* @count: length of buffer
* @ptr: offset (no seek allowed)
*
* Temp_read reports the temperature in degrees Fahrenheit. The API is in
* farenheit. It was designed by an imperial measurement luddite.
*/
static ssize_t wdt_temp_read(struct file *file, char __user *buf,
size_t count, loff_t *ptr)
{
int temperature = wdt_get_temperature();
//把temperature数据拷贝到buf中，传递到应用层
//注意:用户态和内核态之间的数据是不能直接赋值的
//copy_from_user()；是把用户态的数据拷贝到内核态
if (copy_to_user(buf, &temperature, 1))
return -EFAULT;
return 1;
}
/**
* wdt_temp_open:
* @inode: inode of device
* @file: file handle to device
*
* The temperature device has been opened.
*/
static int wdt_temp_open(struct inode *inode, struct file *file)
{
//使用该函数将该文件变成不能seek
return nonseekable_open(inode, file);
}
/**
* wdt_temp_release:
* @inode: inode to board
* @file: file handle to board
*
* The temperature device has been closed.
*/
static int wdt_temp_release(struct inode *inode, struct file *file)
{
return 0;
}
/**
* notify_sys:
* @this: our notifier block
* @code: the event being reported
* @unused: unused
*
* Our notifier is called on system shutdowns. We want to turn the card
* off at reboot otherwise the machine will reboot again during memory
* test or worse yet during the following fsck. This would suck, in fact
* trust me - if it happens it does suck.
*/
static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
void *unused)
{
if (code == SYS_DOWN || code == SYS_HALT)
wdt_stop();
return NOTIFY_DONE;
}
/*
* Kernel Interfaces
*/
static const struct file_operations wdt_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.write = wdt_write,
.unlocked_ioctl = wdt_ioctl,
.open = wdt_open,
.release = wdt_release,
}
static struct miscdevice wdt_miscdev = {
.minor = WATCHDOG_MINOR,//表示次设备号
.name = "watchdog",
.fops = &wdt_fops,
};
//file_opration 是文件操作结构体，许多的字符驱动中都会用到
static const struct file_operations wdt_temp_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = wdt_temp_read,
.open = wdt_temp_open,
.release = wdt_temp_release,
};
//主要是获取温度
static struct miscdevice temp_miscdev = {
.minor = TEMP_MINOR,
.name = "temperature",
.fops = &wdt_temp_fops,
};
/*
* The WDT card needs to learn about soft shutdowns in order to
* turn the timebomb registers off.
*/
/*
通知链表是一个函数链表，链表上的每一个节点都注册了一个函数。
当某个事情发生时，链表上所有节点对应的函数就会被执行。
所以对于通知链表来说有一个通知方与一个接收方。
在通知这个事件时所运行的函数由被通知方决定，
实际上也即是被通知方注册了某个函数，在发生某个事件时这些函数就得到执行。
*/
//wdt需要软重启
static struct notifier_block wdt_notifier = {
.notifier_call = wdt_notify_sys,
};
/**
* cleanup_module:
*
* Unload the watchdog. You cannot do this with any file handles open.
* If your watchdog is set to continue ticking on close and you unload
* it, well it keeps ticking. We won't get the interrupt but the board
* will not touch PC memory so all is fine. You just have to load a new
* module in 60 seconds or reboot.
*/
static void __exit wdt_exit(void)
{
misc_deregister(&wdt_miscdev);
if (type == 501)
misc_deregister(&temp_miscdev);
unregister_reboot_notifier(&wdt_notifier);
free_irq(irq, NULL);
release_region(io, 8);
}
/**
* wdt_init:
*
* Set up the WDT watchdog board. All we have to do is grab the
* resources we require and bitch if anyone beat us to them.
* The open() function will actually kick the board off.
*/
static int __init wdt_init(void)
{
int ret;
if (type != 500 && type != 501) {
pr_err("unknown card type '%d'\n", type);
return -ENODEV;
}
/* Check that the heartbeat value is within it's range;
if not reset to the default */
if (wdt_set_heartbeat(heartbeat)) {
wdt_set_heartbeat(WD_TIMO); //设置成默认值
pr_info("heartbeat value must be 0 < heartbeat < 65536, using %d\n",
WD_TIMO);
}
//这个函数用来申请一块输入输出区域。
//在/proc/ioports文件中可以看到你登记的io口
//参数:1:基地址，2:大小，3:使用该io地址的设备名
if (!request_region(io, 8, "wdt501p")) {
pr_err("I/O address 0x%04x already in use\n", io);
ret = -EBUSY;
goto out;
}
//申请中断
//参数:1:硬件中断号2:中断处理函数3:中断的属性4:中断的名称，通常是设备驱动程序的名称 在cat /proc/interrupts中可以看到此名称
//5:在中断共享时会用到，一般设置为这个设备的设备结构体或者NULL
ret = request_irq(irq, wdt_interrupt, 0, "wdt501p", NULL);
if (ret) {
pr_err("IRQ %d is not free\n", irq);
goto outreg;
}
//注册一个重启通知链
ret = register_reboot_notifier(&wdt_notifier);
if (ret) {
pr_err("cannot register reboot notifier (err=%d)\n", ret);
goto outirq;
}
if (type == 501) {
//注册一个杂项设备
ret = misc_register(&temp_miscdev); //是获取温度的设备
if (ret) {
pr_err("cannot register miscdev on minor=%d (err=%d)\n",
TEMP_MINOR, ret);
goto outrbt;
}
}
ret = misc_register(&wdt_miscdev); //注册看门狗的设备结构体
if (ret) {
pr_err("cannot register miscdev on minor=%d (err=%d)\n",
WATCHDOG_MINOR, ret);
goto outmisc;
}
pr_info("WDT500/501-P driver 0.10 at 0x%04x (Interrupt %d). heartbeat=%d sec (nowayout=%d)\n",
io, irq, heartbeat, nowayout);
if (type == 501)
pr_info("Fan Tachometer is %s\n",
tachometer ? "Enabled" : "Disabled");
return 0;
outmisc:
if (type == 501)
misc_deregister(&temp_miscdev);
outrbt:
unregister_reboot_notifier(&wdt_notifier);
outirq:
free_irq(irq, NULL);
outreg:
release_region(io, 8);
out:
return ret;
}
//驱动开始的位置，也是insmod时第一个调用的函数
module_init(wdt_init);
module_exit(wdt_exit);
//用于驱动的描述，一般情况下，可以没有
MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Driver for ISA ICS watchdog cards (WDT500/501)");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS_MISCDEV(TEMP_MINOR);
MODULE_LICENSE("GPL");
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