2 files changed, 87 insertions, 3 deletions

diff --git a/Documentation/ibm-acpi.txt b/Documentation/ibm-acpi.txt
index cbd3a603a7ef..0132d363feb5 100644
--- a/Documentation/ibm-acpi.txt
+++ b/Documentation/ibm-acpi.txt
@@ -670,6 +670,26 @@ example:
 
         modprobe ibm_acpi hotkey=enable,0xffff video=auto_disable
 
+The ibm-acpi kernel driver can be programmed to revert the fan level
+to a safe setting if userspace does not issue one of the fan commands:
+"enable", "disable", "level" or "watchdog" within a configurable
+ammount of time.  To do this, use the "watchdog" command.
+
+        echo 'watchdog <interval>' > /proc/acpi/ibm/fan
+
+Interval is the ammount of time in seconds to wait for one of the
+above mentioned fan commands before reseting the fan level to a safe
+one.  If set to zero, the watchdog is disabled (default).  When the
+watchdog timer runs out, it does the exact equivalent of the "enable"
+fan command.
+
+Note that the watchdog timer stops after it enables the fan.  It will
+be rearmed again automatically (using the same interval) when one of
+the above mentioned fan commands is received.  The fan watchdog is,
+therefore, not suitable to protect against fan mode changes made
+through means other than the "enable", "disable", and "level" fan
+commands.
+
 
 Example Configuration
 ---------------------
diff --git a/drivers/acpi/ibm_acpi.c b/drivers/acpi/ibm_acpi.c
index 56743c5a0439..e5b8745b9070 100644
--- a/drivers/acpi/ibm_acpi.c
+++ b/drivers/acpi/ibm_acpi.c
@@ -82,6 +82,8 @@
 #include <linux/backlight.h>
 #include <asm/uaccess.h>
 #include <linux/dmi.h>
+#include <linux/jiffies.h>
+#include <linux/workqueue.h>
 
 #include <acpi/acpi_drivers.h>
 #include <acpi/acnamesp.h>
@@ -348,7 +350,8 @@ enum fan_control_access_mode {
 enum fan_control_commands {
         IBMACPI_FAN_CMD_SPEED   = 0x0001,       /* speed command */
         IBMACPI_FAN_CMD_LEVEL   = 0x0002,       /* level command  */
-        IBMACPI_FAN_CMD_ENABLE  = 0x0004,       /* enable/disable cmd */
+        IBMACPI_FAN_CMD_ENABLE  = 0x0004,       /* enable/disable cmd,
+                                                 * and also watchdog cmd */
 };
 
 enum {                                  /* Fan control constants */
@@ -1797,12 +1800,17 @@ static enum fan_control_commands fan_control_commands;
 static int fan_control_status_known;
 static u8 fan_control_initial_status;
 
+static void fan_watchdog_fire(void *ignored);
+static int fan_watchdog_maxinterval;
+static DECLARE_WORK(fan_watchdog_task, fan_watchdog_fire, NULL);
+
 static int fan_init(void)
 {
         fan_status_access_mode = IBMACPI_FAN_NONE;
         fan_control_access_mode = IBMACPI_FAN_WR_NONE;
         fan_control_commands = 0;
         fan_control_status_known = 1;
+        fan_watchdog_maxinterval = 0;
 
         if (gfan_handle) {
                 /* 570, 600e/x, 770e, 770x */
@@ -1934,6 +1942,31 @@ static int fan_get_speed(unsigned int *speed)
         return 0;
 }
 
+static void fan_exit(void)
+{
+        cancel_delayed_work(&fan_watchdog_task);
+        flush_scheduled_work();
+}
+
+static void fan_watchdog_reset(void)
+{
+        static int fan_watchdog_active = 0;
+
+        if (fan_watchdog_active)
+                cancel_delayed_work(&fan_watchdog_task);
+
+        if (fan_watchdog_maxinterval > 0) {
+                fan_watchdog_active = 1;
+                if (!schedule_delayed_work(&fan_watchdog_task,
+                                msecs_to_jiffies(fan_watchdog_maxinterval
+                                                 * 1000))) {
+                        printk(IBM_ERR "failed to schedule the fan watchdog, "
+                               "watchdog will not trigger\n");
+                }
+        } else
+                fan_watchdog_active = 0;
+}
+
 static int fan_read(char *p)
 {
         int len = 0;
@@ -2007,7 +2040,9 @@ static int fan_read(char *p)
         }
 
         if (fan_control_commands & IBMACPI_FAN_CMD_ENABLE)
-                len += sprintf(p + len, "commands:\tenable, disable\n");
+                len += sprintf(p + len, "commands:\tenable, disable\n"
+                               "commands:\twatchdog <timeout> (<timeout> is 0 (off), "
+                               "1-120 (seconds))\n");
 
         if (fan_control_commands & IBMACPI_FAN_CMD_SPEED)
                 len += sprintf(p + len, "commands:\tspeed <speed>"
@@ -2186,6 +2221,21 @@ static int fan_write_cmd_speed(const char *cmd, int *rc)
         return 1;
 }
 
+static int fan_write_cmd_watchdog(const char *cmd, int *rc)
+{
+        int interval;
+
+        if (sscanf(cmd, "watchdog %d", &interval) != 1)
+                return 0;
+
+        if (interval < 0 || interval > 120)
+                *rc = -EINVAL;
+        else
+                fan_watchdog_maxinterval = interval;
+
+        return 1;
+}
+
 static int fan_write(char *buf)
 {
         char *cmd;
@@ -2196,16 +2246,29 @@ static int fan_write(char *buf)
                       fan_write_cmd_level(cmd, &rc)) &&
                     !((fan_control_commands & IBMACPI_FAN_CMD_ENABLE) &&
                       (fan_write_cmd_enable(cmd, &rc) ||
-                       fan_write_cmd_disable(cmd, &rc))) &&
+                       fan_write_cmd_disable(cmd, &rc) ||
+                       fan_write_cmd_watchdog(cmd, &rc))) &&
                     !((fan_control_commands & IBMACPI_FAN_CMD_SPEED) &&
                       fan_write_cmd_speed(cmd, &rc))
                     )
                         rc = -EINVAL;
+                else if (!rc)
+                        fan_watchdog_reset();
         }
 
         return rc;
 }
 
+static void fan_watchdog_fire(void *ignored)
+{
+        printk(IBM_NOTICE "fan watchdog: enabling fan\n");
+        if (fan_set_enable()) {
+                printk(IBM_ERR "fan watchdog: error while enabling fan\n");
+                /* reschedule for later */
+                fan_watchdog_reset();
+        }
+}
+
 static struct ibm_struct ibms[] = {
         {
          .name = "driver",
@@ -2317,6 +2380,7 @@ static struct ibm_struct ibms[] = {
          .read = fan_read,
          .write = fan_write,
          .init = fan_init,
+         .exit = fan_exit,
          .experimental = 1,
          },
 };