Am I correct in assuming that a specific USB device's bus/device allocation is nondeterministic?
Yes.
I have project I am working on in which several USB audio devices will be attached to a Linux PC, each device having a unique audio source. The software running on the machine must handle each audio source seperately and *know* which external source is feeding the device.
When I did some experimentation of unplugging/replugging devices on a specific bus, the device numbers were not reallocated (RHL9, 2.4.20-8). I'm imagining that if I have multiple devices attached to a hub on one of the busses that the order in which device numbers are allocated would be random-ish.
Yes, and could also change due to bus power glitches etc., e.g.
Is there something I'm missing (quite possible), or have I pretty much run into the basics of USB topology?
For Linux 2.6, you could consider using "udev" to see if it will help with persistent device naming (I'm not sure if it helps with all device types).
For Linux 2.4, you are pretty much stuck with reading /proc/bus/usb/devices. It contains topology information, but it
may not contain data to link a /dev/device to its topology info.
(Please note that this is outside the support of a device's serial number since that is not required by the USB 2.0 standard.)
-- ~Randy
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