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-rw-r--r--Documentation/laptops/thinkpad-acpi.txt10
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index f2ff638cce8..0d5e91379ae 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1269,7 +1269,7 @@ Fan control and monitoring: fan speed, fan enable/disable
procfs: /proc/acpi/ibm/fan
sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
- pwm1_enable
+ pwm1_enable, fan2_input
sysfs hwmon driver attributes: fan_watchdog
NOTE NOTE NOTE: fan control operations are disabled by default for
@@ -1282,6 +1282,9 @@ from the hardware registers of the embedded controller. This is known
to work on later R, T, X and Z series ThinkPads but may show a bogus
value on other models.
+Some Lenovo ThinkPads support a secondary fan. This fan cannot be
+controlled separately, it shares the main fan control.
+
Fan levels:
Most ThinkPad fans work in "levels" at the firmware interface. Level 0
@@ -1412,6 +1415,11 @@ hwmon device attribute fan1_input:
which can take up to two minutes. May return rubbish on older
ThinkPads.
+hwmon device attribute fan2_input:
+ Fan tachometer reading, in RPM, for the secondary fan.
+ Available only on some ThinkPads. If the secondary fan is
+ not installed, will always read 0.
+
hwmon driver attribute fan_watchdog:
Fan safety watchdog timer interval, in seconds. Minimum is
1 second, maximum is 120 seconds. 0 disables the watchdog.