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pcwd.c

/*
 * PC Watchdog Driver
 * by Ken Hollis (khollis@bitgate.com)
 *
 * Permission granted from Simon Machell (smachell@berkprod.com)
 * Written for the Linux Kernel, and GPLed by Ken Hollis
 *
 * 960107   Added request_region routines, modulized the whole thing.
 * 960108   Fixed end-of-file pointer (Thanks to Dan Hollis), added
 *          WD_TIMEOUT define.
 * 960216   Added eof marker on the file, and changed verbose messages.
 * 960716   Made functional and cosmetic changes to the source for
 *          inclusion in Linux 2.0.x kernels, thanks to Alan Cox.
 * 960717   Removed read/seek routines, replaced with ioctl.  Also, added
 *          check_region command due to Alan's suggestion.
 * 960821   Made changes to compile in newer 2.0.x kernels.  Added
 *          "cold reboot sense" entry.
 * 960825   Made a few changes to code, deleted some defines and made
 *          typedefs to replace them.  Made heartbeat reset only available
 *          via ioctl, and removed the write routine.
 * 960828   Added new items for PC Watchdog Rev.C card.
 * 960829   Changed around all of the IOCTLs, added new features,
 *          added watchdog disable/re-enable routines.  Added firmware
 *          version reporting.  Added read routine for temperature.
 *          Removed some extra defines, added an autodetect Revision
 *          routine.
 * 961006       Revised some documentation, fixed some cosmetic bugs.  Made
 *              drivers to panic the system if it's overheating at bootup.
 * 961118   Changed some verbiage on some of the output, tidied up
 *          code bits, and added compatibility to 2.1.x.
 * 970912       Enabled board on open and disable on close.
 * 971107   Took account of recent VFS changes (broke read).
 * 971210       Disable board on initialisation in case board already ticking.
 * 971222       Changed open/close for temperature handling
 *              Michael Meskes <meskes@debian.org>.
 * 980112       Used minor numbers from include/linux/miscdevice.h
 * 990403       Clear reset status after reading control status register in
 *              pcwd_showprevstate(). [Marc Boucher <marc@mbsi.ca>]
 * 990605   Made changes to code to support Firmware 1.22a, added
 *          fairly useless proc entry.
 * 990610   removed said useless proc code for the merge <alan>
 * 000403   Removed last traces of proc code. <davej>
 * 011214   Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT <Matt_Domsch@dell.com>
 *              Added timeout module option to override default
 */

/*
 *    A bells and whistles driver is available from http://www.pcwd.de/
 *    More info available at http://www.berkprod.com/ or http://www.pcwatchdog.com/
 */

#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/delay.h>      /* For mdelay function */
#include <linux/timer.h>      /* For timer related operations */
#include <linux/jiffies.h>    /* For jiffies stuff */
#include <linux/miscdevice.h> /* For MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR) */
#include <linux/watchdog.h>   /* For the watchdog specific items */
#include <linux/reboot.h>     /* For kernel_power_off() */
#include <linux/init.h>       /* For __init/__exit/... */
#include <linux/fs.h>         /* For file operations */
#include <linux/isa.h>        /* For isa devices */
#include <linux/ioport.h>     /* For io-port access */
#include <linux/spinlock.h>   /* For spin_lock/spin_unlock/... */

#include <asm/uaccess.h>      /* For copy_to_user/put_user/... */
#include <asm/io.h>           /* For inb/outb/... */

/* Module and version information */
#define WATCHDOG_VERSION "1.20"
#define WATCHDOG_DATE "18 Feb 2007"
#define WATCHDOG_DRIVER_NAME "ISA-PC Watchdog"
#define WATCHDOG_NAME "pcwd"
#define PFX WATCHDOG_NAME ": "
#define DRIVER_VERSION WATCHDOG_DRIVER_NAME " driver, v" WATCHDOG_VERSION " (" WATCHDOG_DATE ")\n"
#define WD_VER WATCHDOG_VERSION " (" WATCHDOG_DATE ")"

/*
 * It should be noted that PCWD_REVISION_B was removed because A and B
 * are essentially the same types of card, with the exception that B
 * has temperature reporting.  Since I didn't receive a Rev.B card,
 * the Rev.B card is not supported.  (It's a good thing too, as they
 * are no longer in production.)
 */
#define     PCWD_REVISION_A         1
#define     PCWD_REVISION_C         2

/*
 * These are the auto-probe addresses available.
 *
 * Revision A only uses ports 0x270 and 0x370.  Revision C introduced 0x350.
 * Revision A has an address range of 2 addresses, while Revision C has 4.
 */
#define PCWD_ISA_NR_CARDS     3
static int pcwd_ioports[] = { 0x270, 0x350, 0x370, 0x000 };

/*
 * These are the defines that describe the control status bits for the
 * PCI-PC Watchdog card.
*/
/* Port 1 : Control Status #1 for the PC Watchdog card, revision A. */
#define WD_WDRST        0x01  /* Previously reset state */
#define WD_T110               0x02  /* Temperature overheat sense */
#define WD_HRTBT        0x04  /* Heartbeat sense */
#define WD_RLY2               0x08  /* External relay triggered */
#define WD_SRLY2        0x80  /* Software external relay triggered */
/* Port 1 : Control Status #1 for the PC Watchdog card, revision C. */
#define WD_REVC_WTRP          0x01  /* Watchdog Trip status */
#define WD_REVC_HRBT          0x02  /* Watchdog Heartbeat */
#define WD_REVC_TTRP          0x04  /* Temperature Trip status */
#define WD_REVC_RL2A          0x08  /* Relay 2 activated by on-board processor */
#define WD_REVC_RL1A          0x10  /* Relay 1 active */
#define WD_REVC_R2DS          0x40  /* Relay 2 disable */
#define WD_REVC_RLY2          0x80  /* Relay 2 activated? */
/* Port 2 : Control Status #2 */
#define WD_WDIS               0x10  /* Watchdog Disabled */
#define WD_ENTP               0x20  /* Watchdog Enable Temperature Trip */
#define WD_SSEL               0x40  /* Watchdog Switch Select (1:SW1 <-> 0:SW2) */
#define WD_WCMD               0x80  /* Watchdog Command Mode */

/* max. time we give an ISA watchdog card to process a command */
/* 500ms for each 4 bit response (according to spec.) */
#define ISA_COMMAND_TIMEOUT     1000

/* Watchdog's internal commands */
#define CMD_ISA_IDLE                0x00
#define CMD_ISA_VERSION_INTEGER           0x01
#define CMD_ISA_VERSION_TENTH       0x02
#define CMD_ISA_VERSION_HUNDRETH    0x03
#define CMD_ISA_VERSION_MINOR       0x04
#define CMD_ISA_SWITCH_SETTINGS           0x05
#define CMD_ISA_RESET_PC            0x06
#define CMD_ISA_ARM_0               0x07
#define CMD_ISA_ARM_30              0x08
#define CMD_ISA_ARM_60              0x09
#define CMD_ISA_DELAY_TIME_2SECS    0x0A
#define CMD_ISA_DELAY_TIME_4SECS    0x0B
#define CMD_ISA_DELAY_TIME_8SECS    0x0C
#define CMD_ISA_RESET_RELAYS        0x0D

/* Watchdog's Dip Switch heartbeat values */
static const int heartbeat_tbl [] = {
      20,   /* OFF-OFF-OFF    = 20 Sec  */
      40,   /* OFF-OFF-ON     = 40 Sec  */
      60,   /* OFF-ON-OFF     =  1 Min  */
      300,  /* OFF-ON-ON      =  5 Min  */
      600,  /* ON-OFF-OFF     = 10 Min  */
      1800, /* ON-OFF-ON      = 30 Min  */
      3600, /* ON-ON-OFF      =  1 Hour */
      7200, /* ON-ON-ON =  2 hour */
};

/*
 * We are using an kernel timer to do the pinging of the watchdog
 * every ~500ms. We try to set the internal heartbeat of the
 * watchdog to 2 ms.
 */

#define WDT_INTERVAL (HZ/2+1)

/* We can only use 1 card due to the /dev/watchdog restriction */
static int cards_found;

/* internal variables */
static atomic_t open_allowed = ATOMIC_INIT(1);
static char expect_close;
static int temp_panic;
static struct {                     /* this is private data for each ISA-PC watchdog card */
      char fw_ver_str[6];           /* The cards firmware version */
      int revision;                 /* The card's revision */
      int supports_temp;            /* Wether or not the card has a temperature device */
      int command_mode;       /* Wether or not the card is in command mode */
      int boot_status;        /* The card's boot status */
      int io_addr;                  /* The cards I/O address */
      spinlock_t io_lock;           /* the lock for io operations */
      struct timer_list timer;      /* The timer that pings the watchdog */
      unsigned long next_heartbeat; /* the next_heartbeat for the timer */
} pcwd_private;

/* module parameters */
#define QUIET     0     /* Default */
#define VERBOSE   1     /* Verbose */
#define DEBUG     2     /* print fancy stuff too */
static int debug = QUIET;
module_param(debug, int, 0);
MODULE_PARM_DESC(debug, "Debug level: 0=Quiet, 1=Verbose, 2=Debug (default=0)");

#define WATCHDOG_HEARTBEAT 0        /* default heartbeat = delay-time from dip-switches */
static int heartbeat = WATCHDOG_HEARTBEAT;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (2<=heartbeat<=7200 or 0=delay-time from dip-switches, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/*
 *    Internal functions
 */

static int send_isa_command(int cmd)
{
      int i;
      int control_status;
      int port0, last_port0;  /* Double read for stabilising */

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "sending following data cmd=0x%02x\n",
                  cmd);

      /* The WCMD bit must be 1 and the command is only 4 bits in size */
      control_status = (cmd & 0x0F) | WD_WCMD;
      outb_p(control_status, pcwd_private.io_addr + 2);
      udelay(ISA_COMMAND_TIMEOUT);

      port0 = inb_p(pcwd_private.io_addr);
      for (i = 0; i < 25; ++i) {
            last_port0 = port0;
            port0 = inb_p(pcwd_private.io_addr);

            if (port0 == last_port0)
                  break;      /* Data is stable */

            udelay (250);
      }

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "received following data for cmd=0x%02x: port0=0x%02x last_port0=0x%02x\n",
                  cmd, port0, last_port0);

      return port0;
}

static int set_command_mode(void)
{
      int i, found=0, count=0;

      /* Set the card into command mode */
      spin_lock(&pcwd_private.io_lock);
      while ((!found) && (count < 3)) {
            i = send_isa_command(CMD_ISA_IDLE);

            if (i == 0x00)
                  found = 1;
            else if (i == 0xF3) {
                  /* Card does not like what we've done to it */
                  outb_p(0x00, pcwd_private.io_addr + 2);
                  udelay(1200);     /* Spec says wait 1ms */
                  outb_p(0x00, pcwd_private.io_addr + 2);
                  udelay(ISA_COMMAND_TIMEOUT);
            }
            count++;
      }
      spin_unlock(&pcwd_private.io_lock);
      pcwd_private.command_mode = found;

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "command_mode=%d\n",
                        pcwd_private.command_mode);

      return(found);
}

static void unset_command_mode(void)
{
      /* Set the card into normal mode */
      spin_lock(&pcwd_private.io_lock);
      outb_p(0x00, pcwd_private.io_addr + 2);
      udelay(ISA_COMMAND_TIMEOUT);
      spin_unlock(&pcwd_private.io_lock);

      pcwd_private.command_mode = 0;

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "command_mode=%d\n",
                        pcwd_private.command_mode);
}

static inline void pcwd_check_temperature_support(void)
{
      if (inb(pcwd_private.io_addr) != 0xF0)
            pcwd_private.supports_temp = 1;
}

static inline void pcwd_get_firmware(void)
{
      int one, ten, hund, minor;

      strcpy(pcwd_private.fw_ver_str, "ERROR");

      if (set_command_mode()) {
            one = send_isa_command(CMD_ISA_VERSION_INTEGER);
            ten = send_isa_command(CMD_ISA_VERSION_TENTH);
            hund = send_isa_command(CMD_ISA_VERSION_HUNDRETH);
            minor = send_isa_command(CMD_ISA_VERSION_MINOR);
            sprintf(pcwd_private.fw_ver_str, "%c.%c%c%c", one, ten, hund, minor);
      }
      unset_command_mode();

      return;
}

static inline int pcwd_get_option_switches(void)
{
      int option_switches=0;

      if (set_command_mode()) {
            /* Get switch settings */
            option_switches = send_isa_command(CMD_ISA_SWITCH_SETTINGS);
      }

      unset_command_mode();
      return(option_switches);
}

static void pcwd_show_card_info(void)
{
      int option_switches;

      /* Get some extra info from the hardware (in command/debug/diag mode) */
      if (pcwd_private.revision == PCWD_REVISION_A)
            printk(KERN_INFO PFX "ISA-PC Watchdog (REV.A) detected at port 0x%04x\n", pcwd_private.io_addr);
      else if (pcwd_private.revision == PCWD_REVISION_C) {
            pcwd_get_firmware();
            printk(KERN_INFO PFX "ISA-PC Watchdog (REV.C) detected at port 0x%04x (Firmware version: %s)\n",
                  pcwd_private.io_addr, pcwd_private.fw_ver_str);
            option_switches = pcwd_get_option_switches();
            printk(KERN_INFO PFX "Option switches (0x%02x): Temperature Reset Enable=%s, Power On Delay=%s\n",
                  option_switches,
                  ((option_switches & 0x10) ? "ON" : "OFF"),
                  ((option_switches & 0x08) ? "ON" : "OFF"));

            /* Reprogram internal heartbeat to 2 seconds */
            if (set_command_mode()) {
                  send_isa_command(CMD_ISA_DELAY_TIME_2SECS);
                  unset_command_mode();
            }
      }

      if (pcwd_private.supports_temp)
            printk(KERN_INFO PFX "Temperature Option Detected\n");

      if (pcwd_private.boot_status & WDIOF_CARDRESET)
            printk(KERN_INFO PFX "Previous reboot was caused by the card\n");

      if (pcwd_private.boot_status & WDIOF_OVERHEAT) {
            printk(KERN_EMERG PFX "Card senses a CPU Overheat. Panicking!\n");
            printk(KERN_EMERG PFX "CPU Overheat\n");
      }

      if (pcwd_private.boot_status == 0)
            printk(KERN_INFO PFX "No previous trip detected - Cold boot or reset\n");
}

static void pcwd_timer_ping(unsigned long data)
{
      int wdrst_stat;

      /* If we got a heartbeat pulse within the WDT_INTERVAL
       * we agree to ping the WDT */
      if(time_before(jiffies, pcwd_private.next_heartbeat)) {
            /* Ping the watchdog */
            spin_lock(&pcwd_private.io_lock);
            if (pcwd_private.revision == PCWD_REVISION_A) {
                  /*  Rev A cards are reset by setting the WD_WDRST bit in register 1 */
                  wdrst_stat = inb_p(pcwd_private.io_addr);
                  wdrst_stat &= 0x0F;
                  wdrst_stat |= WD_WDRST;

                  outb_p(wdrst_stat, pcwd_private.io_addr + 1);
            } else {
                  /* Re-trigger watchdog by writing to port 0 */
                  outb_p(0x00, pcwd_private.io_addr);
            }

            /* Re-set the timer interval */
            mod_timer(&pcwd_private.timer, jiffies + WDT_INTERVAL);

            spin_unlock(&pcwd_private.io_lock);
      } else {
            printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
      }
}

static int pcwd_start(void)
{
      int stat_reg;

      pcwd_private.next_heartbeat = jiffies + (heartbeat * HZ);

      /* Start the timer */
      mod_timer(&pcwd_private.timer, jiffies + WDT_INTERVAL);

      /* Enable the port */
      if (pcwd_private.revision == PCWD_REVISION_C) {
            spin_lock(&pcwd_private.io_lock);
            outb_p(0x00, pcwd_private.io_addr + 3);
            udelay(ISA_COMMAND_TIMEOUT);
            stat_reg = inb_p(pcwd_private.io_addr + 2);
            spin_unlock(&pcwd_private.io_lock);
            if (stat_reg & WD_WDIS) {
                  printk(KERN_INFO PFX "Could not start watchdog\n");
                  return -EIO;
            }
      }

      if (debug >= VERBOSE)
            printk(KERN_DEBUG PFX "Watchdog started\n");

      return 0;
}

static int pcwd_stop(void)
{
      int stat_reg;

      /* Stop the timer */
      del_timer(&pcwd_private.timer);

      /*  Disable the board  */
      if (pcwd_private.revision == PCWD_REVISION_C) {
            spin_lock(&pcwd_private.io_lock);
            outb_p(0xA5, pcwd_private.io_addr + 3);
            udelay(ISA_COMMAND_TIMEOUT);
            outb_p(0xA5, pcwd_private.io_addr + 3);
            udelay(ISA_COMMAND_TIMEOUT);
            stat_reg = inb_p(pcwd_private.io_addr + 2);
            spin_unlock(&pcwd_private.io_lock);
            if ((stat_reg & WD_WDIS) == 0) {
                  printk(KERN_INFO PFX "Could not stop watchdog\n");
                  return -EIO;
            }
      }

      if (debug >= VERBOSE)
            printk(KERN_DEBUG PFX "Watchdog stopped\n");

      return 0;
}

static int pcwd_keepalive(void)
{
      /* user land ping */
      pcwd_private.next_heartbeat = jiffies + (heartbeat * HZ);

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "Watchdog keepalive signal send\n");

      return 0;
}

static int pcwd_set_heartbeat(int t)
{
      if ((t < 2) || (t > 7200)) /* arbitrary upper limit */
            return -EINVAL;

      heartbeat = t;

      if (debug >= VERBOSE)
            printk(KERN_DEBUG PFX "New heartbeat: %d\n",
                   heartbeat);

      return 0;
}

static int pcwd_get_status(int *status)
{
      int control_status;

      *status=0;
      spin_lock(&pcwd_private.io_lock);
      if (pcwd_private.revision == PCWD_REVISION_A)
            /* Rev A cards return status information from
             * the base register, which is used for the
             * temperature in other cards. */
            control_status = inb(pcwd_private.io_addr);
      else {
            /* Rev C cards return card status in the base
             * address + 1 register. And use different bits
             * to indicate a card initiated reset, and an
             * over-temperature condition. And the reboot
             * status can be reset. */
            control_status = inb(pcwd_private.io_addr + 1);
      }
      spin_unlock(&pcwd_private.io_lock);

      if (pcwd_private.revision == PCWD_REVISION_A) {
            if (control_status & WD_WDRST)
                  *status |= WDIOF_CARDRESET;

            if (control_status & WD_T110) {
                  *status |= WDIOF_OVERHEAT;
                  if (temp_panic) {
                        printk(KERN_INFO PFX "Temperature overheat trip!\n");
                        kernel_power_off();
                        /* or should we just do a: panic(PFX "Temperature overheat trip!\n"); */
                  }
            }
      } else {
            if (control_status & WD_REVC_WTRP)
                  *status |= WDIOF_CARDRESET;

            if (control_status & WD_REVC_TTRP) {
                  *status |= WDIOF_OVERHEAT;
                  if (temp_panic) {
                        printk(KERN_INFO PFX "Temperature overheat trip!\n");
                        kernel_power_off();
                        /* or should we just do a: panic(PFX "Temperature overheat trip!\n"); */
                  }
            }
      }

      return 0;
}

static int pcwd_clear_status(void)
{
      int control_status;

      if (pcwd_private.revision == PCWD_REVISION_C) {
            spin_lock(&pcwd_private.io_lock);

            if (debug >= VERBOSE)
                  printk(KERN_INFO PFX "clearing watchdog trip status\n");

            control_status = inb_p(pcwd_private.io_addr + 1);

            if (debug >= DEBUG) {
                  printk(KERN_DEBUG PFX "status was: 0x%02x\n", control_status);
                  printk(KERN_DEBUG PFX "sending: 0x%02x\n",
                        (control_status & WD_REVC_R2DS));
            }

            /* clear reset status & Keep Relay 2 disable state as it is */
            outb_p((control_status & WD_REVC_R2DS), pcwd_private.io_addr + 1);

            spin_unlock(&pcwd_private.io_lock);
      }
      return 0;
}

static int pcwd_get_temperature(int *temperature)
{
      /* check that port 0 gives temperature info and no command results */
      if (pcwd_private.command_mode)
            return -1;

      *temperature = 0;
      if (!pcwd_private.supports_temp)
            return -ENODEV;

      /*
       * Convert celsius to fahrenheit, since this was
       * the decided 'standard' for this return value.
       */
      spin_lock(&pcwd_private.io_lock);
      *temperature = ((inb(pcwd_private.io_addr)) * 9 / 5) + 32;
      spin_unlock(&pcwd_private.io_lock);

      if (debug >= DEBUG) {
            printk(KERN_DEBUG PFX "temperature is: %d F\n",
                  *temperature);
      }

      return 0;
}

/*
 *    /dev/watchdog handling
 */

static int pcwd_ioctl(struct inode *inode, struct file *file,
                  unsigned int cmd, unsigned long arg)
{
      int rv;
      int status;
      int temperature;
      int new_heartbeat;
      int __user *argp = (int __user *)arg;
      static struct watchdog_info ident = {
            .options =        WDIOF_OVERHEAT |
                              WDIOF_CARDRESET |
                              WDIOF_KEEPALIVEPING |
                              WDIOF_SETTIMEOUT |
                              WDIOF_MAGICCLOSE,
            .firmware_version =     1,
            .identity =       "PCWD",
      };

      switch(cmd) {
      default:
            return -ENOTTY;

      case WDIOC_GETSUPPORT:
            if(copy_to_user(argp, &ident, sizeof(ident)))
                  return -EFAULT;
            return 0;

      case WDIOC_GETSTATUS:
            pcwd_get_status(&status);
            return put_user(status, argp);

      case WDIOC_GETBOOTSTATUS:
            return put_user(pcwd_private.boot_status, argp);

      case WDIOC_GETTEMP:
            if (pcwd_get_temperature(&temperature))
                  return -EFAULT;

            return put_user(temperature, argp);

      case WDIOC_SETOPTIONS:
            if (pcwd_private.revision == PCWD_REVISION_C)
            {
                  if(copy_from_user(&rv, argp, sizeof(int)))
                        return -EFAULT;

                  if (rv & WDIOS_DISABLECARD)
                  {
                        return pcwd_stop();
                  }

                  if (rv & WDIOS_ENABLECARD)
                  {
                        return pcwd_start();
                  }

                  if (rv & WDIOS_TEMPPANIC)
                  {
                        temp_panic = 1;
                  }
            }
            return -EINVAL;

      case WDIOC_KEEPALIVE:
            pcwd_keepalive();
            return 0;

      case WDIOC_SETTIMEOUT:
            if (get_user(new_heartbeat, argp))
                  return -EFAULT;

            if (pcwd_set_heartbeat(new_heartbeat))
                  return -EINVAL;

            pcwd_keepalive();
            /* Fall */

      case WDIOC_GETTIMEOUT:
            return put_user(heartbeat, argp);
      }

      return 0;
}

static ssize_t pcwd_write(struct file *file, const char __user *buf, size_t len,
                    loff_t *ppos)
{
      if (len) {
            if (!nowayout) {
                  size_t i;

                  /* In case it was set long ago */
                  expect_close = 0;

                  for (i = 0; i != len; i++) {
                        char c;

                        if (get_user(c, buf + i))
                              return -EFAULT;
                        if (c == 'V')
                              expect_close = 42;
                  }
            }
            pcwd_keepalive();
      }
      return len;
}

static int pcwd_open(struct inode *inode, struct file *file)
{
      if (!atomic_dec_and_test(&open_allowed) ) {
            if (debug >= VERBOSE)
                  printk(KERN_ERR PFX "Attempt to open already opened device.\n");
            atomic_inc( &open_allowed );
            return -EBUSY;
      }

      if (nowayout)
            __module_get(THIS_MODULE);

      /* Activate */
      pcwd_start();
      pcwd_keepalive();
      return nonseekable_open(inode, file);
}

static int pcwd_close(struct inode *inode, struct file *file)
{
      if (expect_close == 42) {
            pcwd_stop();
      } else {
            printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
            pcwd_keepalive();
      }
      expect_close = 0;
      atomic_inc( &open_allowed );
      return 0;
}

/*
 *    /dev/temperature handling
 */

static ssize_t pcwd_temp_read(struct file *file, char __user *buf, size_t count,
                   loff_t *ppos)
{
      int temperature;

      if (pcwd_get_temperature(&temperature))
            return -EFAULT;

      if (copy_to_user(buf, &temperature, 1))
            return -EFAULT;

      return 1;
}

static int pcwd_temp_open(struct inode *inode, struct file *file)
{
      if (!pcwd_private.supports_temp)
            return -ENODEV;

      return nonseekable_open(inode, file);
}

static int pcwd_temp_close(struct inode *inode, struct file *file)
{
      return 0;
}

/*
 *    Kernel Interfaces
 */

static const struct file_operations pcwd_fops = {
      .owner            = THIS_MODULE,
      .llseek           = no_llseek,
      .write            = pcwd_write,
      .ioctl            = pcwd_ioctl,
      .open       = pcwd_open,
      .release    = pcwd_close,
};

static struct miscdevice pcwd_miscdev = {
      .minor =    WATCHDOG_MINOR,
      .name =           "watchdog",
      .fops =           &pcwd_fops,
};

static const struct file_operations pcwd_temp_fops = {
      .owner            = THIS_MODULE,
      .llseek           = no_llseek,
      .read       = pcwd_temp_read,
      .open       = pcwd_temp_open,
      .release    = pcwd_temp_close,
};

static struct miscdevice temp_miscdev = {
      .minor =    TEMP_MINOR,
      .name =           "temperature",
      .fops =           &pcwd_temp_fops,
};

/*
 *    Init & exit routines
 */

static inline int get_revision(void)
{
      int r = PCWD_REVISION_C;

      spin_lock(&pcwd_private.io_lock);
      /* REV A cards use only 2 io ports; test
       * presumes a floating bus reads as 0xff. */
      if ((inb(pcwd_private.io_addr + 2) == 0xFF) ||
          (inb(pcwd_private.io_addr + 3) == 0xFF))
            r=PCWD_REVISION_A;
      spin_unlock(&pcwd_private.io_lock);

      return r;
}

/*
 *  The ISA cards have a heartbeat bit in one of the registers, which
 *  register is card dependent.  The heartbeat bit is monitored, and if
 *  found, is considered proof that a Berkshire card has been found.
 *  The initial rate is once per second at board start up, then twice
 *  per second for normal operation.
 */
static int __devinit pcwd_isa_match(struct device *dev, unsigned int id)
{
      int base_addr=pcwd_ioports[id];
      int port0, last_port0;  /* Reg 0, in case it's REV A */
      int port1, last_port1;  /* Register 1 for REV C cards */
      int i;
      int retval;

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "pcwd_isa_match id=%d\n",
                  id);

      if (!request_region (base_addr, 4, "PCWD")) {
            printk(KERN_INFO PFX "Port 0x%04x unavailable\n", base_addr);
            return 0;
      }

      retval = 0;

      port0 = inb_p(base_addr);     /* For REV A boards */
      port1 = inb_p(base_addr + 1); /* For REV C boards */
      if (port0 != 0xff || port1 != 0xff) {
            /* Not an 'ff' from a floating bus, so must be a card! */
            for (i = 0; i < 4; ++i) {

                  msleep(500);

                  last_port0 = port0;
                  last_port1 = port1;

                  port0 = inb_p(base_addr);
                  port1 = inb_p(base_addr + 1);

                  /* Has either hearbeat bit changed?  */
                  if ((port0 ^ last_port0) & WD_HRTBT ||
                      (port1 ^ last_port1) & WD_REVC_HRBT) {
                        retval = 1;
                        break;
                  }
            }
      }
      release_region (base_addr, 4);

      return retval;
}

static int __devinit pcwd_isa_probe(struct device *dev, unsigned int id)
{
      int ret;

      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "pcwd_isa_probe id=%d\n",
                  id);

      cards_found++;
      if (cards_found == 1)
            printk(KERN_INFO PFX "v%s Ken Hollis (kenji@bitgate.com)\n", WD_VER);

      if (cards_found > 1) {
            printk(KERN_ERR PFX "This driver only supports 1 device\n");
            return -ENODEV;
      }

      if (pcwd_ioports[id] == 0x0000) {
            printk(KERN_ERR PFX "No I/O-Address for card detected\n");
            return -ENODEV;
      }
      pcwd_private.io_addr = pcwd_ioports[id];

      spin_lock_init(&pcwd_private.io_lock);

      /* Check card's revision */
      pcwd_private.revision = get_revision();

      if (!request_region(pcwd_private.io_addr, (pcwd_private.revision == PCWD_REVISION_A) ? 2 : 4, "PCWD")) {
            printk(KERN_ERR PFX "I/O address 0x%04x already in use\n",
                  pcwd_private.io_addr);
            ret=-EIO;
            goto error_request_region;
      }

      /* Initial variables */
      pcwd_private.supports_temp = 0;
      temp_panic = 0;
      pcwd_private.boot_status = 0x0000;

      /* get the boot_status */
      pcwd_get_status(&pcwd_private.boot_status);

      /* clear the "card caused reboot" flag */
      pcwd_clear_status();

      setup_timer(&pcwd_private.timer, pcwd_timer_ping, 0);

      /*  Disable the board  */
      pcwd_stop();

      /*  Check whether or not the card supports the temperature device */
      pcwd_check_temperature_support();

      /* Show info about the card itself */
      pcwd_show_card_info();

      /* If heartbeat = 0 then we use the heartbeat from the dip-switches */
      if (heartbeat == 0)
            heartbeat = heartbeat_tbl[(pcwd_get_option_switches() & 0x07)];

      /* Check that the heartbeat value is within it's range ; if not reset to the default */
      if (pcwd_set_heartbeat(heartbeat)) {
            pcwd_set_heartbeat(WATCHDOG_HEARTBEAT);
            printk(KERN_INFO PFX "heartbeat value must be 2<=heartbeat<=7200, using %d\n",
                  WATCHDOG_HEARTBEAT);
      }

      if (pcwd_private.supports_temp) {
            ret = misc_register(&temp_miscdev);
            if (ret) {
                  printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
                        TEMP_MINOR, ret);
                  goto error_misc_register_temp;
            }
      }

      ret = misc_register(&pcwd_miscdev);
      if (ret) {
            printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
                  WATCHDOG_MINOR, ret);
            goto error_misc_register_watchdog;
      }

      printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
            heartbeat, nowayout);

      return 0;

error_misc_register_watchdog:
      if (pcwd_private.supports_temp)
            misc_deregister(&temp_miscdev);
error_misc_register_temp:
      release_region(pcwd_private.io_addr, (pcwd_private.revision == PCWD_REVISION_A) ? 2 : 4);
error_request_region:
      pcwd_private.io_addr = 0x0000;
      cards_found--;
      return ret;
}

static int __devexit pcwd_isa_remove(struct device *dev, unsigned int id)
{
      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "pcwd_isa_remove id=%d\n",
                  id);

      if (!pcwd_private.io_addr)
            return 1;

      /*  Disable the board  */
      if (!nowayout)
            pcwd_stop();

      /* Deregister */
      misc_deregister(&pcwd_miscdev);
      if (pcwd_private.supports_temp)
            misc_deregister(&temp_miscdev);
      release_region(pcwd_private.io_addr, (pcwd_private.revision == PCWD_REVISION_A) ? 2 : 4);
      pcwd_private.io_addr = 0x0000;
      cards_found--;

      return 0;
}

static void pcwd_isa_shutdown(struct device *dev, unsigned int id)
{
      if (debug >= DEBUG)
            printk(KERN_DEBUG PFX "pcwd_isa_shutdown id=%d\n",
                  id);

      pcwd_stop();
}

static struct isa_driver pcwd_isa_driver = {
      .match            = pcwd_isa_match,
      .probe            = pcwd_isa_probe,
      .remove           = __devexit_p(pcwd_isa_remove),
      .shutdown   = pcwd_isa_shutdown,
      .driver           = {
            .owner      = THIS_MODULE,
            .name = WATCHDOG_NAME,
      },
};

static int __init pcwd_init_module(void)
{
      return isa_register_driver(&pcwd_isa_driver, PCWD_ISA_NR_CARDS);
}

static void __exit pcwd_cleanup_module(void)
{
      isa_unregister_driver(&pcwd_isa_driver);
      printk(KERN_INFO PFX "Watchdog Module Unloaded.\n");
}

module_init(pcwd_init_module);
module_exit(pcwd_cleanup_module);

MODULE_AUTHOR("Ken Hollis <kenji@bitgate.com>, Wim Van Sebroeck <wim@iguana.be>");
MODULE_DESCRIPTION("Berkshire ISA-PC Watchdog driver");
MODULE_VERSION(WATCHDOG_VERSION);
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS_MISCDEV(TEMP_MINOR);

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