linux-kernel - Re: [PATCH v3 1/4] hwmon: (lm90) split set&show temp as common codes

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Message-ID: <51E6392E.5080906@nvidia.com>
Date:	Wed, 17 Jul 2013 14:26:54 +0800
From:	Wei Ni <wni@...dia.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Thierry Reding <thierry.reding@...il.com>,
	Jean Delvare <khali@...ux-fr.org>,
	"rui.zhang@...el.com" <rui.zhang@...el.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 1/4] hwmon: (lm90) split set&show temp as common codes

On 07/17/2013 01:14 PM, Guenter Roeck wrote:
> On Wed, Jul 17, 2013 at 06:26:20AM +0200, Thierry Reding wrote:
>> On Mon, Jul 15, 2013 at 09:24:15AM +0200, Jean Delvare wrote:
>>> On Mon, 15 Jul 2013 14:25:29 +0800, Wei Ni wrote:
>>>> On 07/12/2013 10:40 PM, Guenter Roeck wrote:
>>>>> On Fri, Jul 12, 2013 at 04:30:34PM +0200, Jean Delvare wrote:
>>>>>> If that means that for example the ACPI thermal zone is no longer
>>>>>> displayed by "sensors", then I strongly object - unless it is
>>>>>> explicitly registered as a separate hwmon device from now on, of course.
>>>>>
>>>>> If I recall correctly that was the idea. Of course, in practice that will mean
>>>>> that devices will _not_ get exposed as hwmon devices, as implementers won't
>>>>> bother doing both.
>>>>>
>>>>>> My idea was to make the bridge optional - you decide when you register
>>>>>> a thermal device if it should be exposed as hwmon or not.
>>>>>
>>>>> Yes, that would be a much better solution.
>>>>
>>>> I think we can decide it in the DT, we can add a dt property in the lm90
>>>> device node, such as:
>>>> sys-interface = SYS_HWMON;
>>>> or
>>>> sys-interface = SYS_THERMAL;
>>>> So we register it as the hwmon or thermal device
>>>
>>> This is an option, but please keep in mind that DT is not the only way
>>> to instantiate LM90-like devices, and we should not expose duplicate
>>> inputs by default. It is fine with me if the default is to create only a
>>> HWMON device (as the lm90 driver was doing so far), and only
>>> DT-instantiated devices have the choice.
>>
>> I don't think this information belongs in the device tree. Whether the
>> device is exposed as hwmon or thermal device (or both) is entirely a
>> software issue whereas DT is a means to describe the hardware.
>>
> Correct; this is exactly the type of information which does _not_ belong int
> devicetree.
> 
>> It seems to me that the earlier proposal of communicating to the bridge
>> whether or not a device should be exposed as hwmon device is the right
>> thing to do here.
>>
> Agreed..

Sorry, what's the "bridge" mean, does it mean we need to add a flag in
the thermal_zone_device_register() to indicate if we want to register
virtual hwmon device or not?

Thanks.
Wei.

> 
> Guenter
> 

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