Re: [PATCH 2/3] PERF(kernel): Cleanup power events

[Arjan van de Ven <arjan@linux.intel.com>]

On 10/25/2010 7:36 AM, Thomas Renninger wrote:
>> I know that your new API tries to use "0" as exit, but 0 is already
>> taken (in all power terminology at least on x86 it is) for this.
> cpuidle indeed misuses C0 as "poll idle" state.
> That's really bad/misleading, but nothing that can be changed easily.
>
> I agree shifting C0 (cpuidle)<->  POLL_IDLE event
> and              "not idle"<->  real C0 (executing instructions)
> or however this gets mapped makes things even worse.
>
> Damn, it could be that easy and straight forward, but I agree that
> this kills the approach to trigger state 0 event if C0 is entered
> (C0 as defined as operational mode executing instructions).

ok so we have

"C0 idle"
and
"C0 no longer idle"

I'd propose using the number 0 for the first one (it makes the most 
logical sense, it's the least deep idle state etc etc)

we could use "-1" or "INT_MAX" for the later

but as a user of the API I rather like a separate "we're no longer idle" 
event... but if not, as long as things aren't ambigious I'll find a way 
to code around it.
basically with a separate event, I demultiplex based on event number 
between entry and exit.... with a special exit value I would just need a 
double demultiplex,
one on "idle" and then a second one on the state number to split between 
entry/exit.