Re: PowerOp Design and working patch

Vitaly Wool
2006-08-01T19:28:53Z

On 8/1/06, Tim Bird <tim.bird@am.sony.com> wrote:
> david singleton wrote:
> > On Aug 1, 2006, at 3:09 AM, Matthew Locke wrote:
> >>Well, no one is suggesting a user define and install that info.
> >>Operating point creation will be done by someone who understands the
> >>system (system designer) regardless of the method used to get the
> >>operating points in the kernel.
> >
> > It sounds to me like they don't want to have to change kernel code and
> > recompile the kernel
> > to get a new operating point.
> >
> > It sounds like they are talking about a dynamic operating point as a
> > loadable
> > module, which would fit perfectly with the PowerOp scheme, since it's
> > the
> > system designer who would be creating the new dynamic operating point,
> > not the user.
>
> Often, in the embedded world, the person defining the operating
> states will not be a kernel developer, and may not be comfortable
> with, or capable of, creating a kernel module. (There are
> significant sections of the embedded space where modules are
> not used at all, and no module support is compiled into the
> kernel.) In these cases, requiring loadable module support
> for runtime OPs would be a problem.

In my understanding, runtime OPs should be registered via configfs.
Modules with definitions are worse yet acceptable.

> > The point of PowerOp is that the system designer creates (and validates)
> > the operating points that the hardware vendor supports, not the user.
> >
> > A system designer creating a new operating point as a loadable
> > module would satisfy this requirement, and the user would not
> > be able to put the system into an undefined state, either by accident
> > or maliciously.
> >
>
> OK, I think I understand better your objection to user-space
> created operating points. In embedded projects, it is often
> assumed that no one but the system designer has access to
> arbitrary user space programs. Hence, it sometimes doesn't
> register that an end user could or would utilize a particular
> interface, just because it existed.

Well, why Unix allows root to do 'rm -rf'? It can put the system in an
undefined state... :P

Speaking seriously, if restrictions are comprehensive, then only
correct OPs will be created run-time or whenever. And being able to
create OPs runtime is a very important requirement for PowerOP, for
many reasons.