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thermal: add sanity check for the passive attribute

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Values below 1000 milli-celsius don't make sense and can cause the
system to go into a thermal heart attack: the actual temperature
will always be lower and thus the system will be throttled down to
its lowest setting.

An additional problem is that values below 1000 will show as 0 in
/proc/acpi/thermal/TZx/trip_points:passive.

cat passive
0
echo -n 90 >passive
bash: echo: write error: Invalid argument
echo -n 90000 >passive
cat passive
90000

Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Frans Pop 2009-10-26 08:39:02 +01:00 committed by Len Brown
parent 7fb2616e24
commit 3d8e3ad879
2 changed files with 7 additions and 0 deletions
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1
Documentation/thermal/sysfs-api.txt
View file

@ -206,6 +206,7 @@ passive
passive trip point for the zone. Activation is done by polling with
an interval of 1 second.
Unit: millidegrees Celsius
Valid values: 0 (disabled) or greater than 1000
RW, Optional
*****************************

6
drivers/thermal/thermal_sys.c
View file

@ -225,6 +225,12 @@ passive_store(struct device *dev, struct device_attribute *attr,
if (!sscanf(buf, "%d\n", &state))
return -EINVAL;
/* sanity check: values below 1000 millicelcius don't make sense
* and can cause the system to go into a thermal heart attack
*/
if (state && state < 1000)
return -EINVAL;
if (state && !tz->forced_passive) {
mutex_lock(&thermal_list_lock);
list_for_each_entry(cdev, &thermal_cdev_list, node) {