Gentoo Archives: gentoo-user

From: Joshua Murphy <poisonbl@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Re: Which USB device on which controller?
Date: Fri, 27 Feb 2009 21:20:00
Message-Id: c30988c30902271319j607de2c2p323260de2536ae8a@mail.gmail.com
In Reply to: Re: [gentoo-user] Re: Which USB device on which controller? by Grant
1 On Fri, Feb 27, 2009 at 3:21 PM, Grant <emailgrant@×××××.com> wrote:
2 >>>> I'm looking at the box of one of the webcams and it says "USB 2.0
3 >>>> compatible".
4 >>>>
5 >>>
6 >>> A USB 1.1 device _is_ "USB 2.0 compatible" because a USB 2.0
7 >>> will slow down and run at 1.1 speed.  Does the device say it's
8 >>> "high speed" USB?  "USB 2.0 compatible" generally means it's a
9 >>> USB 1.1 device.
10 >>>
11 >>>
12 >>>> It's not a cable problem because the cable is built right into
13 >>>> the webcam.  I'm not trying to get the webcam to go faster
14 >>>> back and forth to the controller, I just need to make sure I
15 >>>> don't have both webcams on the same OHCI (1.1) USB controller.
16 >>>> I would think buying a USB expansion card would work, but I
17 >>>> have an EHCI (2.0) controller on this system and a second OHCI
18 >>>> (1.1) controller.
19 >>>>
20 >>>> Does anyone have any idea on this.  It really doesn't make sense.
21 >>>>
22 >>>
23 >>> Sounds like it's a 1.1 device to me.
24 >>>
25 >>>
26 >>
27 >> Yep, that's what it sounds like to me too.
28 >>
29 >> Dale
30 >
31 > But that's OK isn't it?  I don't need 2.0 speeds between each webcam
32 > and the controller, I just need the increased overall bandwidth of a
33 > 2.0 controller so one of the 1.1 webcams doesn't use all of it.  I get
34 > the feeling I have a misconception somewhere along the line here.
35 > Could someone straighten me out?
36 >
37 > - Grant
38
39 The controller itself has the full bandwidth of the 2.0 spec, it's
40 just only able to allocate the bandwidth of the 1.0/1.1 spec to each
41 of the cameras because they're being recognized as 1.1 capable only.
42 The controller, though, I'm pretty sure is able to allocate more than
43 enough overall bandwidth to the pair. Based on your original remarks
44 that "one of them isn't functioning", I worry more that there's a
45 problem with the driver for the camera itself that somehow breaks with
46 two of the same camera present, broken udev rule somewhere that's not
47 creating the device for the second camera, or... *something* more
48 along those lines, rather than an issue with the on-chip
49 implementation of your usb controller.
50
51 --
52 Poison [BLX]
53 Joshua M. Murphy