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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2006-11-24 08:47:14 -0500
committerLen Brown <len.brown@intel.com>2006-12-07 01:38:44 -0500
commit16663a87ad1df7022661bc8813b7a2e84e7f5e66 (patch)
treed78d869332bdfa8a5859134114eb145eb41b5dd3 /Documentation
parent778b4d742b210b9cac31f223527f30f1fc70312b (diff)
ACPI: ibm-acpi: implement fan watchdog command
This patch implements a fan control safety watchdog, by request of the authors of userspace fan control scripts. When the watchdog timer expires, the equivalent action of a "fan enable" command is executed. The watchdog timer is reset at every reception of a fan control command that could change the state of the fan itself. This command is meant to be used by userspace fan control daemons, to make sure the fan is never left set to an unsafe level because of userspace problems. Users of the X31/X40/X41 "speed" command are on their own, the current implementation of "speed" is just too incomplete to be used safely, anyway. Better to never use it, and just use the "level" command instead. The watchdog is programmed using echo "watchdog <number>" > fan, where number is the number of seconds to wait before doing an "enable", and zero disables the watchdog. Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ibm-acpi.txt20
1 files changed, 20 insertions, 0 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:
670 670
671 modprobe ibm_acpi hotkey=enable,0xffff video=auto_disable 671 modprobe ibm_acpi hotkey=enable,0xffff video=auto_disable
672 672
673The ibm-acpi kernel driver can be programmed to revert the fan level
674to a safe setting if userspace does not issue one of the fan commands:
675"enable", "disable", "level" or "watchdog" within a configurable
676ammount of time. To do this, use the "watchdog" command.
677
678 echo 'watchdog <interval>' > /proc/acpi/ibm/fan
679
680Interval is the ammount of time in seconds to wait for one of the
681above mentioned fan commands before reseting the fan level to a safe
682one. If set to zero, the watchdog is disabled (default). When the
683watchdog timer runs out, it does the exact equivalent of the "enable"
684fan command.
685
686Note that the watchdog timer stops after it enables the fan. It will
687be rearmed again automatically (using the same interval) when one of
688the above mentioned fan commands is received. The fan watchdog is,
689therefore, not suitable to protect against fan mode changes made
690through means other than the "enable", "disable", and "level" fan
691commands.
692
673 693
674Example Configuration 694Example Configuration
675--------------------- 695---------------------