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

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Date:   Mon, 3 Feb 2020 11:57:18 +0000
From:   Avi Shchislowski <Avi.Shchislowski@....com>
To:     Guenter Roeck <linux@...ck-us.net>
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



> -----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.
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.

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

> > Avi Shchislowski (5):
> >   scsi: ufs: Add ufs thermal support
> >   scsi: ufs: export ufshcd_enable_ee
> >   scsi: ufs: enable thermal exception event
> >   scsi: ufs-thermal: implement thermal file ops
> >   scsi: ufs: temperature atrributes add to ufs_sysfs
> 
> attributes