current powerstate and manually turn on/off?

[M. Warner Losh]

CYIn message: <41BDF8C6.4030607 at root.org>
            Nate Lawson <nate at root.org> writes:
: 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.

I agree.  That's why I said 'strong hint' rather than 'command'.  

Warner