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I see multiple USB controllers in prtconf output for my USB2.0 PCI card. How does this really work?

April 26, 2017card controllers output PCI prtconf USB usb2.0

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I see multiple USB controllers in prtconf output for my USB2.0 PCI card. How does this really work?

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A USB 2.0 controller in fact has 3 (or more) controllers. An ehci controller for USB 2.0 support and 2 ohci or uhci controllers for usb1.x support. If ehci is enabled, it first enumerates the device and if it finds a usb1.x device, it will cause a disconnect and reconnect for one of its companion controllers (ohci or uhci). This is all done in hardware.