Re: [linux-usb-devel] CONFIG_USB_BANDWIDTH broken

[Alan Stern <stern@rowland.harvard.edu>]

On Sun, 25 Dec 2005, Lee Revell wrote:

> CONFIG_USB_BANDWIDTH breaks USB audio.  This has been a problem for at
> least 6 months.
> 
> Typical bug report:
> 
> https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1642
> 
> (search bug tracker for CONFIG_USB_BANDWIDTH to see many more)
> 
> Is anyone working on fixing this?

The bug reports don't mention which USB host controller driver was being 
used.

	With ohci-hcd, bandwidth enforcement works okay.

	With ehci-hcd, there are problems involved with scheduling
	periodic transfers to a full-speed device connected through
	a high-speed hub.  These problems are slowly being fixed.

	With uhci-hcd, bandwidth enforcement has never worked.  New
	changes to the driver (accepted just a few days ago) will
	permit this to be fixed eventually.  It might take a few months
	(plus the time required for the changes to be added to the
	official distribution kernel).

Alan Stern

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