Re: 2.6.23.11 : ehci not working with a710 camera

On Wed, 19 Dec 2007, David Brownell wrote:

> 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.

Or it won't execute the Set-Address without doing a 
Get-Device-Descriptor first.  Or something like that.  I guess you 
could call this "goofing the reset".

Remember, the whole reason for implementing the "new scheme" was that 
some devices didn't work with the "old scheme".  This suggests 
modifying the new scheme may not be a good idea.

Likewise, I have avoided removing the old scheme entirely, because of
one or two reports that some devices appear to need it.  (Those reports
may not be very reliable; any device that doesn't work with the new
scheme probably doesn't work with Windows either.)

Alan Stern


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