CONFIG_USB_BANDWIDTH broken

[Lee Revell]

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?

Lee

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[Alan Stern]

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

[Lee Revell]

On Sun, 2005-12-25 at 22:58 -0500, Alan Stern wrote:
> 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).

Thanks, I'll try to get this info from the users.

So the solution for now is to educate users not to use it (and
especially, distros not to enable it).

Lee

[Alan Stern]

On Sun, 25 Dec 2005, Lee Revell wrote:

> On Sun, 2005-12-25 at 22:58 -0500, Alan Stern wrote:
> > 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.

> Thanks, I'll try to get this info from the users.

>
> So the solution for now is to educate users not to use it (and
> especially, distros not to enable it).

That's right.

Alan Stern