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

[Guenter Roeck]

On 2/3/20 3:57 AM, Avi Shchislowski wrote:
> > -----Original Message-----
> > From: Guenter Roeck <groeck7@xxxxxxxxx> On Behalf Of Guenter Roeck
> > Sent: Sunday, February 2, 2020 9:21 PM
> > To: Avi Shchislowski <Avi.Shchislowski@xxxxxxx>
> > Cc: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>; Avri Altman
> > <Avri.Altman@xxxxxxx>; James E.J. Bottomley <jejb@xxxxxxxxxxxxx>;
> > Martin K. Petersen <martin.petersen@xxxxxxxxxx>; linux-
> > kernel@xxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx
> > 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