Fighting for the power.

Alexander Motin mav at
Mon May 4 07:50:25 UTC 2009

Hans Petter Selasky 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.
> The new USB stack should turn off USB HC's automatically when not in use. At 
> least the schedules will get disabled. Did you do any research on this?

Sorry, I really was testing it only with previous USB stack. Now I can 
acknowledge, that new ehci module loading adds only 0.2W for me by 
default and almost nothing if I power down built-in USB2 web cam 
connected to it using `usbconfig -u 5 -a 2 power_off`.

Great! Thanks!

Alexander Motin

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