ACPI: thinkpad-acpi: add a fan-control feature master toggle

Len Brown considers that an active by default fan control interface in
laptops may be too close to giving users enough rope.  There is a good
chance he is quite correct on this, especially if someone decides to use
that interface in applets and users are not aware of its risks.

This patch adds a master switch to thinkpad-acpi that enables or disables
the entire fan-control feature as a module parameter: "fan_control".  It
defaults to disabled.  Set it to non-zero to enable fan control.

Also, the patch removes the expermiental status from fan control, since it
is stable enough to not be called experimental, and the master switch makes
it safe enough to do so.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 29 insertions, 1 deletions

diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index c0a023cc5ded..7dc3a2206195 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -2935,6 +2935,9 @@ static ssize_t fan_fan_watchdog_store(struct device_driver *drv,
         if (parse_strtoul(buf, 120, &t))
                 return -EINVAL;
 
+        if (!fan_control_allowed)
+                return -EPERM;
+
         fan_watchdog_maxinterval = t;
         fan_watchdog_reset();
 
@@ -3046,6 +3049,14 @@ static int __init fan_init(struct ibm_init_struct *iibm)
                   fan_control_access_mode != TPACPI_FAN_WR_NONE),
                 fan_status_access_mode, fan_control_access_mode);
 
+        /* fan control master switch */
+        if (!fan_control_allowed) {
+                fan_control_access_mode = TPACPI_FAN_WR_NONE;
+                fan_control_commands = 0;
+                dbg_printk(TPACPI_DBG_INIT,
+                           "fan control features disabled by parameter\n");
+        }
+
         /* update fan_control_desired_level */
         if (fan_status_access_mode != TPACPI_FAN_NONE)
                 fan_get_status_safe(NULL);
@@ -3203,6 +3214,9 @@ static void fan_watchdog_reset(void)
 
 static int fan_set_level(int level)
 {
+        if (!fan_control_allowed)
+                return -EPERM;
+
         switch (fan_control_access_mode) {
         case TPACPI_FAN_WR_ACPI_SFAN:
                 if (level >= 0 && level <= 7) {
@@ -3242,6 +3256,9 @@ static int fan_set_level_safe(int level)
 {
         int rc;
 
+        if (!fan_control_allowed)
+                return -EPERM;
+
         rc = mutex_lock_interruptible(&fan_mutex);
         if (rc < 0)
                 return rc;
@@ -3262,6 +3279,9 @@ static int fan_set_enable(void)
         u8 s;
         int rc;
 
+        if (!fan_control_allowed)
+                return -EPERM;
+
         rc = mutex_lock_interruptible(&fan_mutex);
         if (rc < 0)
                 return rc;
@@ -3315,6 +3335,9 @@ static int fan_set_disable(void)
 {
         int rc;
 
+        if (!fan_control_allowed)
+                return -EPERM;
+
         rc = mutex_lock_interruptible(&fan_mutex);
         if (rc < 0)
                 return rc;
@@ -3351,6 +3374,9 @@ static int fan_set_speed(int speed)
 {
         int rc;
 
+        if (!fan_control_allowed)
+                return -EPERM;
+
         rc = mutex_lock_interruptible(&fan_mutex);
         if (rc < 0)
                 return rc;
@@ -3558,7 +3584,6 @@ static struct ibm_struct fan_driver_data = {
         .read = fan_read,
         .write = fan_write,
         .exit = fan_exit,
-        .flags.experimental = 1,
 };
 
 /****************************************************************************
@@ -3879,6 +3904,9 @@ module_param_named(debug, dbg_level, uint, 0);
 static int force_load;
 module_param(force_load, int, 0);
 
+static int fan_control_allowed;
+module_param_named(fan_control, fan_control_allowed, int, 0);
+
 #define IBM_PARAM(feature) \
         module_param_call(feature, set_ibm_param, NULL, NULL, 0)