I have a remote system with a USB device that apparently is prone to
locking up such that it needs to be power cycled (or unplugged and
plugged back in). A reboot of the system is not adequate to bring it
back to life, because the device (apparently) retains power during the
reboot. Does the USB controller in the net4801 permit power to the
devices to be switched off under software control? And if so, do the
Linux drivers support this? I fear the answer is no to at least one
of those questions, because lsusb -v shows this under the hub
descriptor:
No power switching (usb 1.0)
But of course I might be missing something. I do have a
/sys/bus/usb/devices/usb1/power directory, with the following files:
-rw-r--r-- 1 root root 4096 2008-05-04 14:12 autosuspend
-rw-r--r-- 1 root root 0 2008-05-04 14:15 level
-rw-r--r-- 1 root root 4096 2008-05-04 14:12 wakeup
I have tried echo'ing "suspend" into level, as described in the kernel
docs, but I just get a write error. That does work for suspending a
device connected to the hub, but when the device I'm having problems
with locks up, it is no longer even recognized by the system, so
there's no entry in /sys/bus/usb/devices for it for me to try to
suspend it. What I need is a way to get the hub to actually cut power
to the port, not just suspend the device.
So am I missing something, or is this impossible? I wonder also if
there is any way to remotely power cycle the net4801 itself, without
one of those networked power strips designed for that task -- but I
don't remember the BIOS have any option to automatically power-on at a
certain time or anything like that. For that matter, I don't remember
being able to actually power the net4801 off (rather than just halting
the system) any way other than pulling the power cable.
Somebody really needs to come up with an inexpensive ($30) remote
power switch with a USB interface instead of having its own
(expensive) network interface and server firmware -- I'm imagining one
that it would be on by default, and if you gave it a signal via USB,
it would turn off for 30 seconds and then back on again -- this would
allow the host to power cycle itself. Maybe even integrate that with
a watchdog for automatic power cycling if the host doesn't
continuously "ping" the device over the USB link.
TIA for any information.
--
Randall
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