Update on DeviceKit

[Matthew Garrett]

On Thu, May 08, 2008 at 11:09:25PM +0200, Michael Biebl wrote:
> 2008/5/8 Matthew Garrett <mjg59 at srcf.ucam.org>:
> > On Thu, May 08, 2008 at 10:41:40PM +0200, Michael Biebl wrote:
> >> There are a lot of use cases.
> >
> > Yes. They're all wrong.
> 
> I'm not sure if you try to be funny. But I don't think use cases are
> wrong just because you say so.

Well, sure, I guess that "I need to heat my house up, and this laptop is 
the only thing I have" could be counted as a genuine use case. But 
really, the only effect of changing the governor is either to make your 
CPU consume more power or make your CPU generate less heat. I think we 
can agree that the first of these is not a use case we need to care 
about. I can think of two cases where that's interesting. The first is 
if the CPU is overheating. That's either bad hardware or a kernel bug, 
and we shouldn't be trying to fix either of those at the desktop level. 
There are better ways of handling it.

The second is to make the machine quieter, and like I said that's 
actually a much more complicated problem. The right way to deal with it 
isn't to play with the CPU governor, especially since on some machines 
that won't actually make it any quieter - it's easy to make your 
graphics chipset generate lots of heat without putting any significant 
load on the processor. Optimising for quietness is a system-wide issue 
that requires a great deal of knowledge of the hardware. Pushing that 
knowledge into desktop applications means duplication (KDE, GNOME, XFCE 
and so on all end up with their own acoustic daemon) and reduced 
functionality.

So, yes. Anything that wants to alter the cpufreq governor is either 
papering over bugs, doing things at the wrong level or simply doing the 
wrong thing entirely. Any use case that involves the user or desktop 
explicitly setting the cpu governor is therefore wrong. This isn't about 
giving users the freedom to use their computer as they want to, this is 
about not giving users a shotgun that's always aimed at their feet.

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