Re: [PATCH] dell-smm-hwmon.c: Additional temperature sensors

[Michele Sorcinelli <michelesr@autistici.org>]

As far as I know Dell won't help with fixing the SMM layer, they probably
changed something starting with firmware version 1.3.0 and they don't
wanna release information about it.

https://www.hwinfo.com/forum/Thread-Dell-XPS-15-9570-temperatures-not-named-anymore

I wonder if something can be done to force the discovery of the sensors in the driver,
maybe adding a module option to use i8k_get_temp() as probe method as a workaround,
or maybe just forcing that method for this specific model?

Let me know your thoughts.

Thanks,
Michele.

On 12/10/18 10:58 AM, Pali Rohár wrote:
> On Friday 07 December 2018 20:24:49 Guenter Roeck wrote:
>> Anyway, I would like to get some feedback if this can cause regressions
>> on systems which don't support that many sensors and maybe report something
>> completely different if one tries to read the high-numbered sensors.
>> I seem to recall that there was a reason for checking the type and not just
>> trying to read sensor values.
> 
> There can be also different problem for sensors which are turned off.
> E.g. on notebooks with switchable graphic cards which have included
> temperature sensors. When graphic card is turned off, then SMM returns
> error when asking for temperature value (for obvious reason). But
> temperature type still returns correct value "this is GPU sensors".
> 
> So we cannot replace temp_type check by temp_value check. It introduce
> race condition between "starting GPU" and initializing dell-smm hwmon.
> Now linux kernel has support for dynamic turning ON/OFF switchable GPU,
> so we need to care about these race conditions too.
>