Power off for PCI devices

Johannes Hofmann johannes.hofmann at gmx.de
Mon Sep 8 13:25:07 PDT 2008

Hasso Tepper <hasso at estpak.ee> wrote:
> http://leaf.dragonflybsd.org/~hasso/pci-detatch-powerdown.patch
> With this tiny patch power is turned off for PCI devices during detach 
> (ie. when you unload module). It makes is possible to preserve power in 
> laptops (and make them cooler) with unloading network and/or sound device 
> modules not in use and load them only if really needed.
> However, I'm really not sure about all consequences this patch might 
> cause, might knowledge about newbus and friends are still quite limited. 
> Any objections to commit this?
> Tested with em(4), ath(4) and snd_hda(4).

Nice! Do the modules have to be loaded (and then unloaded) for this to
take effect or is it enough to just not load them in the first place?


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