Re: [PATCH RESEND v1] thermal: core: fix blocking in unregistering zone

[Guenter Roeck <linux@roeck-us.net>]

On 4/4/26 10:38, Rafael J. Wysocki wrote:
> On Sat, Apr 4, 2026 at 4:02 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 4/4/26 05:58, Rafael J. Wysocki wrote:
>>> On Fri, Apr 3, 2026 at 4:20 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>>>
>>>> On 4/3/26 05:52, Rafael J. Wysocki wrote:
>>>> .[ ... ]
>>>>> It appears to work for me, but I'm not sure if having multiple hwmon class
>>>>> devices with the same value in the name attribute is fine.
>>>>
>>>> Like this ?
>>>>
>>>> $ cd /sys/class/hwmon
>>>> $ grep . */name
>>>> hwmon0/name:r8169_0_c00:00
>>>> hwmon1/name:nvme
>>>> hwmon2/name:nvme
>>>> hwmon3/name:nct6687
>>>> hwmon4/name:k10temp
>>>> hwmon5/name:spd5118
>>>> hwmon6/name:spd5118
>>>> hwmon7/name:spd5118
>>>> hwmon8/name:spd5118
>>>> hwmon9/name:mt7921_phy0
>>>
>>> Yes.
>>>
>>>> Names such as "r8169_0_c00:00" and "mt7921_phy0" are actually overkill
>>>> since the "sensors" command makes it
>>>>
>>>> r8169_0_c00:00-mdio-0
>>>> Adapter: MDIO adapter
>>>> temp1:        +36.0°C  (high = +120.0°C)
>>>>
>>>> mt7921_phy0-pci-0d00
>>>> Adapter: PCI adapter
>>>> temp1:        +30.0°C
>>>>
>>>> essentially duplicating the device index.
>>>
>>> Well, with the patch posted by me, the output of sensors from a test
>>> system looks like this:
>>>
>>> acpitz-acpi-0
>>> Adapter: ACPI interface
>>> temp1:        +16.8°C
>>>
>>> pch_cannonlake-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +33.0°C
>>>
>>> acpitz-acpi-0
>>> Adapter: ACPI interface
>>> temp1:        +27.8°C
>>>
>>> (some further data excluded), which is kind of confusing (note the
>>> duplicate acpitz-acpi-0 entries with different values of temp1).
>>>
>>
>> Yes, agreed, that is confusing. I would have expected the second one
>> to be identified as "acpitz-acpi-1". Do they both have the same parent ?
> 
> No, they don't.
> 
> The parent of each of them is a thermal zone device and both parents
> have the same "type" value.
> 
>>> That could be disambiguated by concatenating the thermal zone ID
>>> (possibly after a '_') to the name.  Or the "temp*" things for thermal
>>> zones of the same type could carry different numbers.
>>>
>>> A less attractive alternative would be to register a special virtual
>>> device serving as a parent for all hwmon interfaces registered
>>> automatically for thermal zones.
>>
>> If they all have the same parent, technically it should be a single
>> hwmon device with multiple sensors, as in:
>>
>> acpitz-acpi-0
>> Adapter: ACPI interface
>> temp1:        +16.8°C
>> temp2:        +27.8°C
> 
> So somebody tried to make it look like that by registering hwmon
> interfaces for all of the thermal zones of the same type under one of
> them, but that (quite obviously) doesn't work.

Not sure I understand why that doesn't work or why that is obvious,
but I'll take you by your word (I would agree that the current
_implementation_ looks problematic).

I looked into the source code of the "sensors" command. It indeed does
not index ACPI devices (nor virtual devices, for that matter) but
assumes that such devices are unique. My apologies for not realizing
this earlier.

So your only option is indeed to index the chip name if you want/need
more than one hwmon device with the same base name (here: acpitz)
instantiated from the thermal subsystem.

One comment to one of your earlier e-mails:

"However, it is more of a design issue IMV because putting temperature
  attributes for all of the (possibly unrelated) thermal zones of the
  same type under one hwmon interface is not particularly useful"

A single hardware monitoring device, by design, serves multiple
thermal zones. Anything else would not make sense for multi-channel
hardware monitoring chips. The hardware monitoring subsystem groups
sensors by chip, not by thermal zones.

Having said this: This discussion is not new. Certain subsystems
advocate for having one hardware monitoring device per sensor,
not per chip. One submitter went as far as telling me that I am
clueless. We don't need to repeat the exercise. I have my opinion,
you have yours, and all we can do is to agree to disagree.

Thanks,
Guenter