Re: [gentoo-user] Powering down the USB controller

[Paul Hartman]

On Fri, Dec 28, 2012 at 10:45 PM, Grant <emailgrant@×××××.com> wrote:
> I'm trying to get a USB sound card to behave in a certain way which
> requires it to think the computer has gone to sleep.  I'm told the
> specific signal the sound card looks for is if the USB controller has
> been physically powered down.  Should I unload a kernel module to
> accomplish this, or do I need to actually put the computer into sleep
> mode?

I don't think you can turn USB port off, at best you can suspend it,
which is not truly 100% powered-down. I think you might be able to
power off an entire hub (and never power it back on again until
reboot) but I'm not sure if that will be any better than just
unplugging the cable. You might be able to build some kind of simple
USB on/off switch. :)

Check out /sys/bus/usb/devices/[yourdevice]/power/level for current
status and you can echo different commands to that same file to
attempt to change its status. Check out the power management settings
and documentation in the linux kernel for your options.