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, 2 insertions, 0 deletions

diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index 8348fc653009..a9e709368256 100644
--- a/drivers/misc/thinkpad_acpi.h
+++ b/drivers/misc/thinkpad_acpi.h
@@ -375,6 +375,8 @@ enum fan_control_commands {
                                                  * and also watchdog cmd */
 };
 
+static int fan_control_allowed;
+
 static enum fan_status_access_mode fan_status_access_mode;
 static enum fan_control_access_mode fan_control_access_mode;
 static enum fan_control_commands fan_control_commands;