current powerstate and manually turn on/off?

[Nate Lawson]

M. Warner Losh wrote:
> In message: <41BDF6A7.3040702 at root.org>
>             Nate Lawson <nate at root.org> writes:
> : Warner Losh wrote:
> : >>By using sysctl, I do know what's the current powerstate
> : >>of each device. I wounder is there any command or sysctl
> : >>that can manually turn device on or off?
> : > 
> : > 
> : > Not really, no.
> : 
> : I think this is something the drivers should handle and we don't need to 
> : add user access to power states since it's probably the biggest way to 
> : shoot yourself in the foot.  We already power down devices with no 
> : driver attached and once drivers get smart about powering down devices 
> : that are idle, this would cover all scenarios.
> 
> It would be nice to have a way to say "This is a really strong hint
> that you are now idle, go to lowest power, highest latency to get out
> of it mode."

I believe the driver itself has best knowledge of this, based on 
refcount, recent I/O, etc.  You don't want the user turning off things 
without the driver's knowledge.

-- 
Nate