On Sun, 18 Dec 2005, Tommi Niemi wrote:
> Hi, thanks for helping w/ this.
>
> Here is usbmon output when I connect plain HUB (There is embedded USB
> audio module inside monitor, but I'm not sure does it works at all)
...
> After this I connect mouse to the hub, no output at all.
>
> Here is usbmon output when I connect HUB (CF memory stick is connected
> to the hub)
... Essentially the same.
Okay, I see the problem.
In your previous email message, the system log included this line when you
plugged in the hub:
hub 3-1:1.0: no power switching (usb 1.0)
That information is confirmed by the usbmon data. It means the hub is
telling your computer that it cannot control the power supply to its ports
-- which means the power is always on.
But later in the usbmon output, when the computer asks for the port
status, the hub sends a reply indicating that the power is off. That's
why the devices you plug in don't get detected. Since there's no power to
the ports, the hub can't tell when you plug in a device.
When a device lies about its capabilities, you've got to expect that it
won't work right.
No doubt Windows tells the hub to turn on port power, in spite of the fact
that the hub says it's unable to control the power. Perhaps Linux should
do that also, perhaps not.
Anyway, if you want to change the kernel's behavior, you can do it by
editing the drivers/usb/core/hub.c source file. Find the subroutine named
hub_power_on, where it says:
/* if hub supports power switching, enable power on each port */
if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2) {
Change the "if" statement to something that will never fail, like:
if (1) {
That should get your hub going.
Alan Stern
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