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hwmon: (acpi_power_meter) Fix 4.29 MW bug

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The ACPI specification says:

"If an error occurs while obtaining the meter reading or if the value
is not available then an Integer with all bits set is returned"

Since the "integer" is 32 bits in case of the ACPI power meter,
userspace will get a power reading of 2^32 * 1000 miliwatts (~4.29 MW)
in case of such an error. This was discovered due to a lm_sensors
bugreport (https://github.com/lm-sensors/lm-sensors/issues/460).
Fix this by returning -ENODATA instead.

Tested-by: <urbinek@gmail.com>
Fixes: de584afa5e ("hwmon driver for ACPI 4.0 power meters")
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20231124182747.13956-1-W_Armin@gmx.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Armin Wolf 2023-11-24 19:27:47 +01:00 committed by Guenter Roeck
parent 58ebe7fb6e
commit 1fefca6c57
1 changed files with 4 additions and 0 deletions
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4
drivers/hwmon/acpi_power_meter.c
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@ -31,6 +31,7 @@
#define POWER_METER_CAN_NOTIFY (1 << 3)
#define POWER_METER_IS_BATTERY (1 << 8)
#define UNKNOWN_HYSTERESIS 0xFFFFFFFF
#define UNKNOWN_POWER 0xFFFFFFFF
#define METER_NOTIFY_CONFIG 0x80
#define METER_NOTIFY_TRIP 0x81
@ -348,6 +349,9 @@ static ssize_t show_power(struct device *dev,
update_meter(resource);
mutex_unlock(&resource->lock);
if (resource->power == UNKNOWN_POWER)
return -ENODATA;
return sprintf(buf, "%llu\n", resource->power * 1000);
}