Re: [PATCH 3/3] hwmon: (coretemp) Add temp%d_fault sysfs attribute

[sashiko-bot@kernel.org]

> The temp%d_input sysfs attribute reports the CPU core temperature
> regardless of the valid bit (bit 31) in IA32_[PACKAGE]_THERM_STATUS.
> Commit bf6ea084ebb5 ("hwmon: (coretemp) Do not return -EAGAIN for low
> temperatures") established this behavior after observing that some Intel
> CPUs do not set the valid bit while the temperature is too low to be
> measured. The value reported is of more use than an error. Changing this is
> not an option: the interface is long-established and userspace relies on
> it never failing.
> 
> Userspace, however, cannot distinguish a genuinely low temperature from
> one the CPU could not measure. Until that commit it could: reading
> temp%d_input returned -EAGAIN. That signal was removed and nothing
> replaced it. Report the inverse of the valid bit through the standard hwmon
> temp%d_fault attribute. Its documented meaning is that the measurement
> for that channel should not be trusted. Tools built on libsensors consume
> the standard attribute.
> 
> temp%d_input continues to ignore the valid bit. A new update_temp() helper
> refreshes the cached temperature and its fault state together, so both
> attributes are served from the same reading of the status register.
> 
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260924-coretemp-temp-fault-v1-0-1884f0ff97d5@linux.intel.com?part=3