RE: [linux-usb] Re: USB device allocation

David Waite (mass@ufl.edu)
Thu, 7 Oct 1999 22:20:17 -0400


> If the bus has to be probed periodically, it can be triggered in
> userspace.
> I am not aware how this currently happens. USB/PCMCIA folks help here?

I believe on USB the hub driver does this, although I am not sure. I believe
it is the purpose of a 1 time/second interrupt, to probe for new hardware.

I see something like this (although I am whipping up an idea here off the
top of my head, so it will probably have major flaws):

1. Device gets added/removed
2. hardware driver gets notified, now knows to give file errors on
read/write.
3. userspace daemon is notified, removes file link.

on (re)insertion is more difficult:
1. hardware driver gets notified, processes any device info and tries to see
if there is a unique serial number.
2. device is temporarily mapped as a new device
2. driver notifies userspace daemon
3. userspace daemon processes configuration, decides if the device should be
considered the same as a previous device
4. device is either re-added (read/write work again), or left as a new
device.
5. userspace daemon adds file link

-David Waite

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