Re: [linux-usb-devel] Re: EHCI TT bandwidth (was Re: [PATCH]USB_BANDWIDTH documentation change)

From: Lee Revell
Date: Fri Dec 30 2005 - 14:15:26 EST


On Fri, 2005-12-30 at 14:13 -0500, Dan Streetman wrote:
> On Thu, 29 Dec 2005, Lee Revell wrote:
>
> >How do I test them? Should this make USB audio work with
> >CONFIG_USB_BANDWIDTH?
>
> It won't have any effect on CONFIG_USB_BANDWIDTH, as the EHCI transaction
> translator scheudling code doesn't care about that config setting. This
> also won't have any effect on USB 2.0 devices (e.g. a highspeed Audio
> device).
>
> The updates will only help in the situation where there are multiple
> lowpseed or fullspeed devices with periodic endpoints, all connected to
> the same USB 2.0 (highspeed) hub. In that situation it's possible to
> "fill up" the USB 2.0 hub's transaction translator periodic schedule with
> only a few devices. The updates allow many more devices to fit in the
> TT's periodic schedule. The specific number of devices depends on how
> many periodic endpoints, those endpoint's poll rates, and their max packet
> sizes.
>

OK. For some reason I though that problem was fixed, I guess it was a
different issue. ALSA users previously reported that a full speed audio
device didn't work at all through a high speed hub at all but that it
was fixed a few months ago.

Lee

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