Re: [patch 2/2] libata: power off unused ports

[Kristen Carlson Accardi <kristen.c.accardi@intel.com>]

On 28 Mar 2008 08:43:40 +0100
Andi Kleen <andi@firstfloor.org> wrote:

> Kristen Carlson Accardi <kristen.c.accardi@intel.com> writes:
> 
> > If a port doesn't support hot plug, there's no reason to keep the phy powered
> > on unoccupied ports.  
> 
> Would it be possible to add some writable sysfs attribute for this too?
> 
> A lot of ports support hot plug, but the users knows they will never actually
> hot plug anything there. Exposing it to sysfs would make sense so 
> someone could make a conscious decision to save these watts by sacrifying
> hotplug-support.
> 
> -Andi
> 

I had thought about extending the sysfs interface for link power 
management to include a new value: off.  Right now we have
min_power, medium_power, and max_performance - we could add
a value for just "off" which means the port is inactive -
but then we'd have to change all the sysfs stuff to check
and see if the user is turning the port back on after it's
been off and then re-init everything, so it might be a large
effort, so if we did that I'd say it should be a separate
effort from this patch series.