[Bug 296710] Re: warning: ehci_hcd loaded AFTER uhci_hcd and ohci_hcd

[Scott James Remnant]

On Tue, 2009-04-07 at 18:02 +0000, Jeffrey Baker wrote:

> > Whether or not they're built in or modules, you can still disable
> > individual host control interfaces - the method is just slightly
> > different (though since the one that works for built-ins ALSO works for
> > modules, we should arguably be documenting that one instead of the
> > blacklist trick).
> 
> OK, I should research this.  A laptop user can save energy by
> unloading the hcd modules, which puts the corresponding PCI functions
> into D3.
> 
Actually, the same effect can be achieved by enabling autosuspend on the
USB devices (including the hub).  See:

http://www.lesswatts.org/projects/devices-power-management/usb.php

This is the kind of thing we can't turn on just before release, but I
suspect that's a good target for Karmic.

>   How can you achieve the same thing with the drivers
> built-in?
> 
You can disable the host controller itself by unbinding it from the
driver, for example:

# cd /sys/bus/pci/drivers/ehci_hcd
# ls
0000:00:1d.7  bind  module  new_id  uevent  unbind
# echo -n 0000:00:1d.7 > unbind
# ls
bind  module  new_id  uevent  unbind

Scott
-- 
Scott James Remnant
scott at canonical.com

-- 
warning: ehci_hcd loaded AFTER uhci_hcd and ohci_hcd
https://bugs.launchpad.net/bugs/296710
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