Re: [PATCH v5 00/33] New thermal OF code

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Guenter Roeck <linux@roeck-us.net>, Michael Walle <michael@walle.cc>
Cc: daniel.lezcano@linexp.org, abailon@baylibre.com,
	anarsoul@gmail.com, baolin.wang7@gmail.com,
	bjorn.andersson@linaro.org, broonie@kernel.org,
	damien.lemoal@opensource.wdc.com, digetx@gmail.com,
	f.fainelli@gmail.com, glaroque@baylibre.com,
	hayashi.kunihiko@socionext.com, heiko@sntech.de,
	j-keerthy@ti.com, jonathanh@nvidia.com, khilman@baylibre.com,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	lukasz.luba@arm.com, matthias.bgg@gmail.com,
	mcoquelin.stm32@gmail.com, mhiramat@kernel.org,
	miquel.raynal@bootlin.com, niklas.soderlund@ragnatech.se,
	rafael@kernel.org, rui.zhang@intel.com, shawnguo@kernel.org,
	talel@amazon.com, thierry.reding@gmail.com,
	tiny.windzz@gmail.com
Subject: Re: [PATCH v5 00/33] New thermal OF code
Date: Tue, 9 Aug 2022 17:37:17 +0200	[thread overview]
Message-ID: <53d33f48-1774-3a0e-a84e-a8027679ea5a@linaro.org> (raw)
In-Reply-To: <6318d099-268b-1bbe-fed8-4f4b356e90cb@roeck-us.net>

On 09/08/2022 16:32, Guenter Roeck wrote:
> On 8/9/22 01:53, Daniel Lezcano wrote:
>> Hi Guenter,
>>
>> On 08/08/2022 12:26, Guenter Roeck wrote:
>>
>> [ ... ]
>>
>>>> But I guess even if that is fixed, the driver will not probe due to the
>>>> missing trip points? Are they now mandatory? Does it mean we'd need to
>>>> update our device trees? But that will then mean older devices trees
>>>> don't work anymore.
>>>
>>> It would also mean that all hwmon drivers registering a thermal zone 
>>> sensor
>>> would fail to register unless such a thermal zone actually exists. 
>>
>> Probably missing something but if the thermal zone is not described, 
>> the hwmon driver won't initialize. And except if I'm wrong, that was 
>> already the case before these changes, no?
>>
> 
> In the hwmon source (you point to it below):
> 
>          if (IS_ERR(tzd)) {
>                  if (PTR_ERR(tzd) != -ENODEV)
>                          return PTR_ERR(tzd);
>                  dev_info(dev, "temp%d_input not attached to any thermal 
> zone\n",
>                           index + 1);
>                  devm_kfree(dev, tdata);
>                  return 0;
>          }
> 
> That contradicts "if the thermal zone is not described, the hwmon driver 
> won't initialize".
> Now I must be missing something, since you mention that yourself below, 
> and your new patch
> series fixes the problem, at least AFAICS. Confused.

Sorry for not being clear. Let me try to explain it differently.

The function hwmon_thermal_add_sensor() is calling:

Without "[PATCH v5 00/33] New thermal OF code":
-----------------------------------------------

   devm_thermal_zone_of_sensor_register(dev, index, ...);

If there is no thermal zone description or the 'dev' does not belong to 
any thermal zone then -ENODEV is returned -> OK and the hwmon thermal 
zone is _not_ created

With "[PATCH v5 00/33] New thermal OF code":
--------------------------------------------

  devm_thermal_of_zone_register(dev, index, ...);

If there is no thermal zone description or the 'dev' does not belong to 
any thermal zone then *-EINVAL* is returned -> NOK, error message, and 
hwmon thermal zone is _not_ created

With "[PATCH v5 00/33] New thermal OF code" + fixes:
----------------------------------------------------

  devm_thermal_of_zone_register(dev, index, ...);

If there is no thermal zone description or the 'dev' does not belong to 
any thermal zone then *-ENODEV* is returned -> OK and the hwmon thermal 
zone is _not_ created

Quoting your initial message:

"It would also mean that all hwmon drivers registering a thermal zone 
sensor would fail to register unless such a thermal zone actually 
exists. This would make the whole concept of having the hwmon core 
register thermal zone sensors impossible [...]"

The thermal zone must be described if the OF registering function 
variant is used. Except I'm wrong that was already the case before the 
changes.

Otherwise, nothing prevents a hwmon to register itself with the core 
code, that will create the thermal zone.

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