USB physical ports

Chad J. Milios milios at
Fri Sep 11 14:44:25 UTC 2015

> On Sep 11, 2015, at 5:45 AM, Shane Ambler <FreeBSD at ShaneWare.Biz> wrote:
>> On 11/09/2015 09:18, Ernie Luzar wrote:
>> Dave wrote:
>>>> On Thursday 10 September 2015 11:43:03 Ernie Luzar wrote:
>>>> Hello List;
>>>> I have 6 physical ports on my PC box. The boot time messages seem to
>>>> say that one of those ports is 480Mbps High Speed USB v2.0.
>>>> How do I determine which physical USB port is the 480Mbps High Speed
>>>> port?
> I think inserting a device is the only way to identify which port it is
> inserted into, use usbconfig to see what is connected at what speed.

Yeah unfortunately there is little rhyme or reason between device tree the kernel enumerates as seen in dmesg output and physical ports on front/back/sides/inside computer. Some of the things FreeBSD sees may not be USB ports/hubs/devices at all, in the typical sense, and instead are certain features of your motherboard that just happen to be connected by USB at an electric and/or protocol level. And some of the real physical ports actually get shared by USB "hubs" built into the motherboard physically or simulated by mixtures of firmware and other types of bridges and busses.

Test what you need to test in order to be sure your system will run how you really intend. 480 Mbps or 5 Gbps on each port one at a time may work great but then down the road you discover you can only do a total of x bps to ports a thru b while simultaneously doing y bps thru ports c thru d and the combinations are endless. Many desktop/server mobos have numerous extra USB connectors on the mobo, minus the actual ports, (for ten cent adapters added once you need them or tiny devices meant for those internal connectors).

Good mobos from good manufacturers should have block diagrams you can trust but matching them up to actual kernel probes is not an exact or consistent science from product SKU to product SKU and you'd be darn lucky when the manufacturer doesn't mix it up between different batches of the same SKU.

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