Am Sonntag, 4. Februar 2007 17:07 schrieb Alan Stern:
> On Sat, 3 Feb 2007, Oliver Neukum wrote:
>
> > If you want simplicity, I'd suggest serialization. kmalloc for 4 bytes
> > is overkill. I think it is even faster if we block on the cases there's
> > a collision that go through kmalloc/kfree each time.
>
> On the other hand, the same routine calls usb_control_message() which does
> two kmallocs: one for the URB and one for the usb_ctrlrequest structure.
> Adding a third for the buffer wouldn't be so bad.
That is not a good reason to make matters even worse.
> Or we could pre-allocate everything; the ctrlrequest could even share the
> same cacheline as the I/O buffer. But most hubs are idle almost all the
> time, and it doesn't seem worthwhile to allocate permanently one URB per
> hub if it will hardly ever be used.
You've changed that with autosuspend.
Regards
Oliver
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