// SPDX-License-Identifier: GPL-2.0+ /* * Acquire Single Board Computer Watchdog Timer driver * * Based on wdt.c. Original copyright messages: * * (c) Copyright 1996 Alan Cox <[email protected]>, * All Rights Reserved. * * 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 <[email protected]> * * 14-Dec-2001 Matt Domsch <[email protected]> * Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT * Can't add timeout - driver doesn't allow changing value */ /* * Theory of Operation: * The Watch-Dog Timer is provided to ensure that standalone * Systems can always recover from catastrophic conditions that * caused the CPU to crash. This condition may have occurred by * external EMI or a software bug. When the CPU stops working * correctly, hardware on the board will either perform a hardware * reset (cold boot) or a non-maskable interrupt (NMI) to bring the * system back to a known state. * * The Watch-Dog Timer is controlled by two I/O Ports. * 443 hex - Read - Enable or refresh the Watch-Dog Timer * 043 hex - Read - Disable the Watch-Dog Timer * * To enable the Watch-Dog Timer, a read from I/O port 443h must * be performed. This will enable and activate the countdown timer * which will eventually time out and either reset the CPU or cause * an NMI depending on the setting of a jumper. To ensure that this * reset condition does not occur, the Watch-Dog Timer must be * periodically refreshed by reading the same I/O port 443h. * The Watch-Dog Timer is disabled by reading I/O port 043h. * * The Watch-Dog Timer Time-Out Period is set via jumpers. * It can be 1, 2, 10, 20, 110 or 220 seconds. */ /* * Includes, defines, variables, module parameters, ... */ #define pr_fmt(fmt) … /* Includes */ #include <linux/module.h> /* For module specific items */ #include <linux/moduleparam.h> /* For new moduleparam's */ #include <linux/types.h> /* For standard types (like size_t) */ #include <linux/errno.h> /* For the -ENODEV/... values */ #include <linux/kernel.h> /* For printk/panic/... */ #include <linux/miscdevice.h> /* For struct miscdevice */ #include <linux/watchdog.h> /* For the watchdog specific items */ #include <linux/fs.h> /* For file operations */ #include <linux/ioport.h> /* For io-port access */ #include <linux/platform_device.h> /* For platform_driver framework */ #include <linux/init.h> /* For __init/__exit/... */ #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ #include <linux/io.h> /* For inb/outb/... */ /* Module information */ #define DRV_NAME … #define WATCHDOG_NAME … /* There is no way to see what the correct time-out period is */ #define WATCHDOG_HEARTBEAT … /* internal variables */ /* the watchdog platform device */ static struct platform_device *acq_platform_device; static unsigned long acq_is_open; static char expect_close; /* module parameters */ /* You must set this - there is no sane way to probe for this board. */ static int wdt_stop = …; module_param(wdt_stop, int, 0); MODULE_PARM_DESC(…) …; /* You must set this - there is no sane way to probe for this board. */ static int wdt_start = …; module_param(wdt_start, int, 0); MODULE_PARM_DESC(…) …; static bool nowayout = … WATCHDOG_NOWAYOUT; module_param(nowayout, bool, 0); MODULE_PARM_DESC(…) …; /* * Watchdog Operations */ static void acq_keepalive(void) { … } static void acq_stop(void) { … } /* * /dev/watchdog handling */ static ssize_t acq_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { … } static int acq_open(struct inode *inode, struct file *file) { … } static int acq_close(struct inode *inode, struct file *file) { … } /* * Kernel Interfaces */ static const struct file_operations acq_fops = …; static struct miscdevice acq_miscdev = …; /* * Init & exit routines */ static int __init acq_probe(struct platform_device *dev) { … } static void acq_remove(struct platform_device *dev) { … } static void acq_shutdown(struct platform_device *dev) { … } static struct platform_driver acquirewdt_driver = …; static int __init acq_init(void) { … } static void __exit acq_exit(void) { … } module_init(…) …; module_exit(acq_exit); MODULE_AUTHOR(…) …; MODULE_DESCRIPTION(…) …; MODULE_LICENSE(…) …;
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