hwmon: (acpi_power_meter) Check for 32-bit and 64-bit unknown ACPI values

According to the ACPI specification (Section 10.4), ACPI Power Meter
objects (_PMC capability fields, _PMM, _GHL, _PAI) report unknown or
unavailable integer values using an integer with all bits set, which can
be either U32_MAX (0xffffffff) or U64_MAX (0xffffffffffffffff) depending
on the DSDT revision.

Currently, only hwmon_power_average checks both 32-bit and 64-bit
unknown sentinels:
- power1_cap_hyst_show() only compares res->caps.hysteresis against the
  32-bit UNKNOWN_HYSTERESIS (0xffffffff), so a 64-bit U64_MAX sentinel
  bypasses the check, overflows when multiplied by 1000, and emits a
  bogus number instead of "unknown".
- power1_accuracy_show() does not check for unknown sentinels at all,
  formatting 0xffffffff as "4294967.295%".
- power_meter_read() does not check min_avg_interval, max_avg_interval,
  avg_interval, min_cap, max_cap, or cap for unknown sentinels, exposing
  scaled or overflowed values (or negative values when cast to signed
  long) to userspace instead of returning -ENODATA.
- get_power_alarm_state() does not check whether resource->cap is
  unknown before comparing resource->power > resource->cap.
- update_meter() passes an unknown caps.sampling_time directly to
  msecs_to_jiffies(), caching sensor readings for weeks on 64-bit builds.

Introduce acpi_power_meter_is_unknown() to check for both U32_MAX and
U64_MAX, and use it across sysfs attribute handlers and meter updates:
- Return -ENODATA in power_meter_read() when numeric power, interval, or
  cap attributes report an unknown value.
- Emit "unknown" in power1_cap_hyst_show() and power1_accuracy_show()
  when hysteresis or accuracy is unknown.
- Avoid comparing against an unknown cap in get_power_alarm_state(),
  returning 0 (no alarm, no error) unless a hardware capping
  notification was latched.
- Skip the sampling_time cache window in update_meter() when
  sampling_time is unknown.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: de584afa5e18 ("hwmon driver for ACPI 4.0 power meters")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions