linux-kernel - Re: [PATCH 0/5] scsi: ufs: ufs device as a temperature sensor

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Date:   Mon, 3 Feb 2020 06:47:54 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Avi Shchislowski <Avi.Shchislowski@....com>
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <Avri.Altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH 0/5] scsi: ufs: ufs device as a temperature sensor

On 2/3/20 3:57 AM, Avi Shchislowski wrote:
> 
> 
>> -----Original Message-----
>> From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
>> Sent: Sunday, February 2, 2020 9:21 PM
>> To: Avi Shchislowski <Avi.Shchislowski@....com>
>> Cc: Alim Akhtar <alim.akhtar@...sung.com>; Avri Altman
>> <Avri.Altman@....com>; James E.J. Bottomley <jejb@...ux.ibm.com>;
>> Martin K. Petersen <martin.petersen@...cle.com>; linux-
>> kernel@...r.kernel.org; linux-scsi@...r.kernel.org
>> Subject: Re: [PATCH 0/5] scsi: ufs: ufs device as a temperature sensor
>>
>   
>> On Sun, Feb 02, 2020 at 12:46:54PM +0200, Avi Shchislowski wrote:
>>> UFS3.0 allows using the ufs device as a temperature sensor. The
>>> purpose of this feature is to provide notification to the host of the
>>> UFS device case temperature. It allows reading of a rough estimate
>>> (+-10 degrees centigrade) of the current case temperature, And setting
>>> a lower and upper temperature bounds, in which the device will trigger
>>> an applicable exception event.
>>>
>>> We added the capability of responding to such notifications, while
>>> notifying the kernel's thermal core, which further exposes the thermal
>>> zone attributes to user space. UFS temperature attributes are all
>>> read-only, so only thermal read ops (.get_xxx) can be implemented.
>>>
>>
>> Can you add an explanation why this can't be added to the just-introduced
>> 'drivetemp' driver in the hwmon subsystem, and why it make sense to have
>> proprietary attributes for temperature and temperature limits ?
>>
>> Thanks,
>> Guenter
>>
> Hi Guenter
> 
> Thank you for your comment
> 
> The ufs device is not a temperature sensor per-se.  It is, first and foremost, a storage device.

Huh ? Many non-temperature-sensor devices in the kernel report their temperature
through the hardware monitoring subsystem.

> Reporting the device case temperature is a feature added in a recently released UFS spec (UFS3.0).
> Therefore, adding a thermal-core module, in opposed to hwmon module, seemed more appropriate.
> Registering a hwmon device look excessive, as no other hw-monitoring attribute is available - aside temperature.
> 
Really ? Interesting position. Are you saying that instantiating a thermal core
module, plus providing non-standard sysfs attributes to report the temperature,
is less complex ? Are you sure ? Can you provide evidence that this is indeed
the case ?

> Using Martin's tree, I wasn't able to locate the 'drivetemp' module, nor any reference to  it in the hwmon documentation.
> 

You might want to consider looking in the mainline kernel.

Guenter