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SubjectRe: [PATCH 1/2] USB: EHCI: Move sysfs related bits into ehci-sysfs.c
On Wed, 29 Jun 2011, Kirill Smelkov wrote:

> > Also, when decreasing the schedule limit, do you think it is really
> > necessary to check that the current allocation doesn't exceed the new
> > limit? I think it would be sufficient to apply the new limit just to
> > new bandwidth allocation requests. After all, this API is meant for
> > experts only.
>
> I think yes, it is needed. E.g. because there is this check in
> periodic_usecs():
>
> #ifdef DEBUG
> if (usecs > ehci->uframe_periodic_max)
> ehci_err (ehci, "uframe %d sched overrun: %d usecs\n",
> frame * 8 + uframe, usecs);
> #endif
> return usecs;
> }
>
> and periodic_usecs() is called in e.g. this chain:
>
> itd_submit
> iso_stream_schedule
> itd_slot_ok
> periodic_usecs
>
> and others.

That won't matter unless DEBUG is defined.

> I'd leave this check as is - to me it would be useful in debug mode to
> verify that we've not overallocated a period.
>
> Also, even if this knob would be useful only to experts, it would be
> better to put feedback onto the knob so that people could know whether
> thir request could be served or not.
>
> What do you think?

Can you make that check conditional on DEBUG being set?

Alan Stern



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