Re: Weird Dell SMM bug since 6.18

[Armin Wolf <W_Armin@gmx.de>]

Am 22.03.26 um 11:18 schrieb Guy Boldon:

> Hi Guenter,
>
> Thank you for the explanations, much appreciated.
>
>
> On Thu Mar 19, 2026 at 4:52 PM CET, Guenter Roeck wrote:
>> The use of -ENODATA in hwmon to report that a value is not available is
>> relatively new and isn't even fully documented in the sysfs ABI (admittedly
>> a major oversight). The major driver for its use is that it more accurately
>> reflects reality as reported by the "sensors" command if an attribute value
>> is not available (sensors reports "N/A" instead of an error message if it
>> gets an -ENODATA error).
> Ah, it seemed somewhat new and that makes sense. -ENODATA converts to
> a clean N/A without an error message. We will adjust to handle -ENODATA
> going forward.

Nice, sounds like a good plan to me.

Thanks,
Armin Wolf

>>> As a related point: gpd_fan returns -EOPNOTSUPP rather than -ENODATA
>>> when in auto mode, and documents that behavior in the kernel docs. The
>> Please feel free to submit a patch to fix that.
> I'll submit a patch for that.
>
>> The best we can do is to find a means to improve consistency, but as you
>> can see here even that is difficult because different people will have
>> different opinions on how that consistency should look like. Error response
>> will vary, as will attribute visibility.
>>
>> If you would like to get actively involved, please feel free to submit patches
>> improving the documentation (Documentation/hwmon/sysfs-interface.rst,
>> Documentation/ABI/testing/sysfs-class-hwmon, and or driver specific
>> documentation) as well as driver patches to help improve consistency across
>> drivers.
> I agree and I would like to help improve consistency for the interface. I'll
> look at the docs as well. CoolerControl is a direct consumer of this interface
> across a large range of drivers, but improving consistency, I think, benefits
> anyone interacting with more than a handful of drivers.
>
> Thanks again,
> Guy
>
>