Re: 2.6.23.11 : ehci not working with a710 camera

[David Brownell <david-b@xxxxxxxxxxx>]

On Wednesday 19 December 2007, Alan Stern wrote:
> On Wed, 19 Dec 2007, David Brownell wrote:
> 
> > Here's that patch.  Please give it at try with USB_DEBUG enabled.
> > Note that the patch has two behavioral changes -- avoid the "what
> > maxpacket should I use?" dance that's not needed, and use a longer
> > delay at one point -- plus a diagnostic change to make EHCI report
> > what control transfers are making trouble.
> > 
> > We should at least be able to find out just what calls are making
> > the trouble (and at what point in the sequence), even if the behavior
> > changes don't help.  :)
> 
> I agree it's worth trying this.  For the future, however, I would be
> cautious about removing that "determine maxpacket" code for low- and
> high-speed devices.  Windows uses it always, regardless of the device
> speed, and quite likely some devices won't work without it.

I'm trying to understand the failure mode you imply:

	<reset>
   (a)
	Read device descriptor, 64 bytes worth (too big)
		--> returns 18 bytes "short" packet
	<reset>
   (b)
	Set address
	Read device desriptor, 18 byte worth
		--> returns 18 bytes "exact match"

What's removed is the stuff between (a) and (b) right?  So if a
device can notice a difference, it's because it goofs the reset.

- Dave

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