On Tue, 21 Oct 2008
rliou@... wrote:
> I need to detect if my USB 2.0 device is connected through a USB 1.1
> hub so I can handle the device accordingly. The value of bcdUSB in
> the descriptor and device qualifier always shows me 200H(USB 2.0)
> with or without the hub. How do I get the actual USB speed for a
> device with a low/full speed hub in the middle?
I don't think there's any direct way to do it with libusb.
You can use an indirect technique. For example, if a device is running
at high speed then all Bulk endpoints must have a maxpacket size of
512, whereas at full speed all Bulk endpoints must have a maxpacket
size <= 64.
Or you could parse the contents of /proc/bus/usb/devices if you're
running on a Linux system. That file contains the actual speed of
each USB device (among a lot of other information). Or you can get the
speed through sysfs.
Alan Stern
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