Re: How to understand USB displays in device manager
From: Doron Holan [MS] (doronh_at_nospam.microsoft.com)
Date: 03/09/05
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Date: Tue, 8 Mar 2005 23:15:34 -0800
let me remphasize what marc said. change the view in device manager to "By
Connection". All will become clear to you. Every hub has a fixed number of
ports. The ports themselves are not enumerated if they are empty. When
something is plugged in, the device that is plugged into the port is
enumerated, not the port itself. Think of an empty PCI slot. When there is
no device plugged into it, you do not see an "Empty PCI slot" device in
device manager. The same applies to an empty USB port on a USB hub.
Do not confuse device class with device functinality. Device class is used
for logical groupings, not functional groupings. Many usb devices install
under the usb class because there is no other appropriate class to be
installed under.
d
-- Please do not send e-mail directly to this alias. this alias is for newsgroup purposes only. This posting is provided "AS IS" with no warranties, and confers no rights. "Marc Reinig" <Marco@newsgroups.nospam> wrote in message news:u5%23C68DJFHA.2784@TK2MSFTNGP09.phx.gbl... >> 1) "USB Root Hub" is displayed to show empty USB ports. When USB device >> is connected to one of these ports, USB peripheral device driver will >> be displayed replacing "USB Root Hub" display because port is now >> connected. > > No, "USB Root Hubs" don't disappear, they are devices in themselves. Each > Host Controller will have it's own Root Hub. Each Root Hub represents one > individual USB bus (Universal Serial Bus bus?). > >> 2) If (1) is true, > > It's not. > >> when I connected my GreenHills USB probe, it didnot >> replace any of "USB Root Hub" > > It wouldn't, nothing would cause that. > >> but instead added a display entry under >> "Universal Serial Bus controllers". Curious, I looked into INF file and >> class=USB. > > Class, USB, includes USB host controllers and USB hubs, but not USB > peripherals. > >> So I dont understand how to interpret this. Probe is >> definitely a USB peripheral device. > Yes, a hub or host controller are USB devices, but they are also in a > special class as far as setup classes go and thus are treated differently. > The USB in the INF file identifies them as such. > >> 3)Are the number of USB ports available for device connection are same >> as "USB Root Hub" displayed? What about controllers? > > No, you can have a root hub with several ports. They are all on the same > bus. Devices connected to different root hubs are on different busses. > > In device manager, chose View/ Devices by Connection. You'll find the > controllers under ACPI .... /Microsoft ACPI-Compliant system/PCI bus. > > Marco > ________________________ > Marc Reinig > UCO/Lick Observatory > Laboratory for Adaptive Optics > >
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