On 5/13/2016 10:39 AM, Nicolas Pinault wrote:
Le 13/05/2016 à 15:10, Jeffrey Nichols a écrit :
On 5/13/2016 9:03 AM, Nicolas Pinault wrote:
Le 12/05/2016 à 17:15, Wander Lairson Costa a écrit :
2016-05-12 11:40 GMT-03:00 Nicolas Pinault<nicol...@aaton.com>:
Hi,
Is it possible to retrieve USB bus topology with PyUSB ?
Yes, you will need to use the Device object "port_number" and "bus" properties.
While it is enough for my application, I don't see how to
reconstruct the USB tree with just "port_number".
There's also "port_numbers", assuming you're using a somewhat recent
libusb-1.0 version as your backend. Combine that with the bus
attribute, and you can get a representation of the physical
attachment point of the device.
I already tried to use "port_numbers" but this field was always blank.
After updating libusb-1.0, this field is not blank anymore.
What I don't understand is that bus/port_number numbers are not unique.
On my system :
IdVendor8086 IdProduct=1E26 bus=1 Address=1 port=0
IdVendor8086 IdProduct=1E2D bus=2 Address=1 port=0
* IdVendor0204 IdProduct=6025 bus=1 Address=6 port=1 ports = (1, 6, 1)
IdVendor0424 IdProduct=2513 bus=1 Address=2 port=6 ports = (1, 6)
+ IdVendor046D IdProduct=C061 bus=2 Address=5 port=1 ports = (1, 1)
IdVendor0529 IdProduct=0001 bus=1 Address=4 port=5 ports = (1, 5)
IdVendor2CFF IdProduct=0002 bus=1 Address=5 port=2 ports = (1, 6, 2)
IdVendor413C IdProduct=2107 bus=2 Address=2 port=2 ports = (1, 2)
+ IdVendor8087 IdProduct=0024 bus=2 Address=4 port=1 ports = (1,)
* IdVendor8087 IdProduct=0024 bus=1 Address=3 port=1 ports = (1,)
IdVendor8564 IdProduct=4000 bus=3 Address=20 port=8 ports = (8,)
IdVendor8086 IdProduct=1E31 bus=3 Address=1 port=0
The lines marked with a + or a * contains same bus/port_number numbers.
Only port_numbers field is different.
What does this mean ?
When the bus is different, they're on totally different USB buses
(presumably this corresponds internally to USB root hubs, I'm not sure
of the technical details). That's always the first level of differentiation.
The port always corresponds to the final number in the ports tuple. It's
the port number on the last hub in the hierarchy. It's not unique enough
to use to distinguish positions in the hierarchy (even when combined
with bus), and not terribly useful in my opinion.
I use the tuple (bus, port_numbers) in my application to determine a
device's physical location, so when I tell a device to reboot into
bootloader mode I can find the new device in the same location (as a
device anywhere else could not be the one I'm looking for).
Jeff
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