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SubjectRe: [DRIVER][RFC] SC1200 Watchdog driver
Here's a finalised version, with the recommended changes (including 
probe). ISAPNP to follow shortly. Alan, regarding that race in ioctl,
read/write. Wouldn't the open semaphore protect against that in this case.
Otherwise irq safe spinlocks could be added to read/write.

/*
* National Semiconductor PC87307/PC97307 (ala SC1200) WDT driver
* (c) Copyright 2002 Zwane Mwaikambo <zwane@commfireservices.com>,
* All Rights Reserved.
* Based on wdt.c and wdt977.c by Alan Cox and Woody Suwalski respectively.
*
* 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.
*
* The author(s) of this software shall not be held liable for damages
* of any nature resulting due to the use of this software. This
* software is provided AS-IS with no warranties.
*
* Changelog:
* 20020220 Zwane Mwaikambo Code based on datasheet, no hardware.
* 20020221 Zwane Mwaikambo Cleanups as suggested by Jeff Garzik and Alan Cox.
* 20020222 Zwane Mwaikambo Added probing.
*/

#include <linux/config.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <asm/semaphore.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>

#define SC1200_MODULE_VER "build 20020222"
#define SC1200_MODULE_NAME "sc1200wdt"
#define PFX SC1200q_MODULE_NAME ": "

#define MAX_TIMEOUT 255 /* 255 minutes */
#define PMIR (io) /* Power Management Index Register */
#define PMDR (io+1) /* Power Management Data Register */

/* Data Register indexes */
#define FER1 0x00 /* Function enable register 1 */
#define FER2 0x01 /* Function enable register 2 */
#define PMC1 0x02 /* Power Management Ctrl 1 */
#define PMC2 0x03 /* Power Management Ctrl 2 */
#define PMC3 0x04 /* Power Management Ctrl 3 */
#define WDTO 0x05 /* Watchdog timeout register */
#define WDCF 0x06 /* Watchdog config register */
#define WDST 0x07 /* Watchdog status register */

/* WDO Status */
#define WDO_ENABLED 0x00
#define WDO_DISABLED 0x01

/* WDCF bitfields - which devices assert WDO */
#define KBC_IRQ 0x01 /* Keyboard Controller */
#define MSE_IRQ 0x02 /* Mouse */
#define UART1_IRQ 0x03 /* Serial0 */
#define UART2_IRQ 0x04 /* Serial1 */
/* 5 -7 are reserved */

static char banner[] __initdata = KERN_INFO PFX SC1200_MODULE_VER " timeout = %d min(s)\n";
static int timeout = 1; /* default to 1 minute (0 - 255), 0 disables it */
static int io;
struct semaphore open_sem;

MODULE_PARM(io, "i");
MODULE_PARM_DESC(io, "io port");
MODULE_PARM(timeout, "i");
MODULE_PARM_DESC(timeout, "range is 0-255 minutes, default is 1");

/* Read from Data Register */
static inline void sc1200wdt_read_data(unsigned char index, unsigned char *data)
{
outb_p(index, PMIR);
*data = inb(PMDR);
}

/* Write to Data Register */
static inline void sc1200wdt_write_data(unsigned char index, unsigned char data)
{
outb_p(index, PMIR);
outb(data, PMDR);
}

/* this returns the status of the WDO signal, inactive high
* returns WDO_ENABLED or WDO_DISABLED
*/
static inline int sc1200wdt_status(void)
{
unsigned char ret;

sc1200wdt_read_data(WDST, &ret);
return (ret & 0x01); /* bits 1 - 7 are undefined */
}

static int sc1200wdt_open(struct inode *inode, struct file *file)
{
unsigned char reg;

/* allow one at a time */
if (down_trylock(&open_sem))
return -EBUSY;

#ifdef CONFIG_WATCHDOG_NOWAYOUT
MOD_INC_USE_COUNT;
#endif

if (timeout > MAX_TIMEOUT)
timeout = MAX_TIMEOUT;

sc1200wdt_read_data(WDCF, &reg);
/* assert WDO when any of the following interrupts are triggered too */
reg |= (KBC_IRQ | MSE_IRQ | UART1_IRQ | UART2_IRQ);
sc1200wdt_write_data(WDCF, reg);
/* set the timeout and get the ball rolling */
sc1200wdt_write_data(WDTO, timeout);
printk(KERN_INFO PFX "Watchdog enabled");

return 0;
}

static int sc1200wdt_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
int new_timeout;
static struct watchdog_info ident = {
options: WDIOF_SETTIMEOUT,
firmware_version: 0,
identity: "PC87307/PC97307"
};

switch (cmd) {
default:
return -ENOTTY; /* Keep Pavel Machek amused ;) */

case WDIOC_GETSUPPORT:
if (copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident)))
return -EFAULT;
return 0;

case WDIOC_GETSTATUS:
return put_user(sc1200wdt_status(), (int *)arg);

case WDIOC_KEEPALIVE:
sc1200wdt_write_data(WDTO, timeout);
return 0;

case WDIOC_SETTIMEOUT:
if (get_user(new_timeout, (int *)arg))
return -EFAULT;

/* the API states this is given in secs */
new_timeout /= 60;
if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
return -EINVAL;

timeout = new_timeout;
sc1200wdt_write_data(WDTO, timeout);
/* fall through and return the new timeout */

case WDIOC_GETTIMEOUT:
return put_user(timeout * 60, (int *)arg);
}
}

static int sc1200wdt_release(struct inode *inode, struct file *file)
{
#ifndef CONFIG_WATCHDOG_NOWAYOUT
/* Disable it on the way out */
sc1200wdt_write_data(WDTO, 0);
printk(KERN_INFO PFX "Watchdog disabled\n");
#endif
up(&open_sem);

return 0;
}

static ssize_t sc1200wdt_write(struct file *file, const char *data, size_t len, loff_t *ppos)
{
if (ppos != &file->f_pos)
return -ESPIPE;

if (len) {
sc1200wdt_write_data(WDTO, timeout);
return 1;
}

return 0;
}

static int sc1200wdt_notify_sys(struct notifier_block *this, unsigned long code, void *unused)
{
if (code == SYS_DOWN || code == SYS_HALT)
sc1200wdt_write_data(WDTO, 0);

return NOTIFY_DONE;
}

static struct notifier_block sc1200wdt_notifier =
{
notifier_call: sc1200wdt_notify_sys,
notifier_block: NULL,
priority: 0
};

#ifndef MODULE
static int __init sc1200wdt_setup(char *str)
{
int ints[4];

str = get_options (str, ARRAY_SIZE(ints), ints);

if (ints[0] > 0)
{
io = ints[1];
if (ints[0] > 1)
timeout = ints[2];
}

return 1;
}

__setup("sc1200wdt=", sc1200wdt_setup);
#endif /* MODULE */

static struct file_operations sc1200wdt_fops =
{
owner: THIS_MODULE,
write: sc1200wdt_write,
ioctl: sc1200wdt_ioctl,
open: sc1200wdt_open,
release: sc1200wdt_release,
};

static struct miscdevice sc1200wdt_miscdev =
{
minor: WATCHDOG_MINOR,
name: "watchdog",
fops: &sc1200wdt_fops,
};

static int __init sc1200wdt_probe(void)
{
/* The probe works by reading the PMC3 register's default value of 0x0e
* there is one caveat, if the device disables the parallel port or any
* of the UARTs we won't be able to detect it.
* Nb. This could be done with accuracy by reading the SID registers, but
* we don't have access to those io regions.
*/

unsigned char reg;

sc1200wdt_read_data(PMC3, &reg);
reg &= 0x0f; /* we don't want the UART busy bits */
return (reg == 0x0e) ? 0 : -ENODEV;
}

static int __init sc1200wdt_init(void)
{
int ret;

printk(banner, timeout);

if (!request_region(io, 2, SC1200_MODULE_NAME)) {
printk(KERN_ERR PFX "IO port %#x not free.\n", io);
ret = -EBUSY;
goto out_clean;
}

ret = sc1200wdt_probe();
if (ret == -ENODEV)
goto out_io;

ret = register_reboot_notifier(&sc1200wdt_notifier);
if (ret) {
printk(KERN_ERR PFX "Unable to register reboot notifier err = %d\n", ret);
goto out_io;
}

sema_init(&open_sem, 1);
ret = misc_register(&sc1200wdt_miscdev);
if (ret) {
printk(KERN_ERR PFX "Unable to register miscdev on minor %d\n", WATCHDOG_MINOR);
goto out_rbt;
}

out_clean:
return ret;

out_rbt:
unregister_reboot_notifier(&sc1200wdt_notifier);
out_io:
release_region(io, 2);
goto out_clean;
}

static void __exit sc1200wdt_exit(void)
{
misc_deregister(&sc1200wdt_miscdev);
unregister_reboot_notifier(&sc1200wdt_notifier);
release_region(io, 2);
}

module_init(sc1200wdt_init);
module_exit(sc1200wdt_exit);

MODULE_AUTHOR("Zwane Mwaikambo <zwane@commfireservices.com>");
MODULE_DESCRIPTION("Driver for National Semiconductor PC87307/PC97307 watchdog component");
MODULE_LICENSE("GPL");
EXPORT_NO_SYMBOLS;


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