Fighting for the power.

Alexander Motin mav at
Mon May 4 09:51:11 UTC 2009

Paul B. Mahol wrote:
> On 5/4/09, Alexander Motin <mav at> wrote:
>> 2. PCI devices
>> PCI bus provides method to control device power. For example, I have
>> completely no use for my FireWire controller and most of time - EHCI USB
>> controller. Disabling them allows me to save about 3W of power. To
>> disable all unneeded PCI devices you should build kernel without their
>> drivers and add to loader.conf:
>> hw.pci.do_power_nodriver=3
>> To enable devices back all you need to do is just load their drivers as
>> modules.
> Unloading modules doesnt put them back into into D3 state.
> You are forced to load some another module again to put wanted device
> into D3 state.

Yes. Resume also does not powers down unowned devices. Would be good to 
fix that also.

Alexander Motin

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