Re: [lm-sensors] hwmon API update

[Matthew Garrett <mjg59@srcf.ucam.org>]

On Mon, Feb 14, 2011 at 11:33:55AM -0800, Guenter Roeck wrote:
> On Mon, Feb 14, 2011 at 02:05:57PM -0500, Matthew Garrett wrote:
> > The kernel has generic support for thermal management. Making it work 
> > for any device is just a matter of a driver generating the appropriate 
> > thermal and cooling devices and associating them. ACPI already works 
> > this way.
> > 
> Not sure what you suggest here. Thermal devices register as hwmon devices
> if so configured, so having hwmon devices register as thermal devices
> would not work, at least not without some serious thought to prevent
> registration loops.

That's really an implementation detail - the worst case at present is 
that you'd end up with the same sensor providing data twice, but that's 
fixable.

> If you are looking for thermal device support, maybe the drivers in question 
> should be implemented as thermal device drivers and provide hwmon functionality
> through the thermal subsystem. Did you consider that option ?

We could definitely change the existing hwmon drivers to be thermal 
drivers instead, but not everything they do fits into that model.

> Do you plan to use/utilize the thermal subsystem, or do you plan to duplicate
> that functionality in the GPU driver(s) ? Guess that was one of the reasons
> why Jean asked for a use case of the proposed API.

Use the thermal subsystem. That's why I made the ACPI thermal code 
generic in the first place.

> If you plan to use the thermal subsystem without having to rewrite hwmon drivers,
> did you consider means to interconnect the hwmon subsystem with the thermal subsystem,
> eg by creating a means for hwmon devices to register as thermal devices ?

As I said, we could rework the hwmon drivers into thermal devices
instead, but we'd still need a mechanism for providing the thermal 
device back to the registering device.

> > Because hardware control is the kernel's job, not userspace's. Having 
> > hardware melt just because userspace fell off a cliff isn't acceptable.
> > 
> The same argument would apply to system fan control, doesn't it ?

Yes, which is why it belongs in the kernel.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

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