Re: [PATCH 1/2] USB: EHCI: Move sysfs related bits into ehci-sysfs.c

[Alan Stern]

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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