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List:       freebsd-current
Subject:    Re: [PATCH] Fix for USB ugen panics
From:       Jay Cornwall <jay () evilrealms ! net>
Date:       2004-01-09 2:17:09
Message-ID: 3FFE0F25.3040201 () evilrealms ! net
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Martin wrote:

> or from a sourceforge-project:
> http://sourceforge.net/project/showfiles.php?group_id=10775&release_id=43893

> In section 7.5.3 "Bandwidth Management" it says something about
> "Set Configuration" request and the zero-setting. Maybe I 
> misunderstood the paragraph.

"...by providing a zero-bandwidth interface (alternate setting zero) and 16 
alternate settings interfaces wth 8Mbps down to 0.5Mbps bandwidth in 
descending 0.5Mbps steps."

These can be accessed through USB_SET_ALTINTERFACE with a value from 0 to 16.

"The default alternate setting zero (with zero bandwidth) selected by a Set 
Configuration request..."

I think this is the badly phrased sentence in question. What the author is 
trying to say is that alternate interface 0 will be selected by default upon 
USB_SET_CONFIGURATION - which seems a bit daft without explaining which 
configurations are available. Try a USB_SET_CONFIGURATION of 1, and see if the 
16 interfaces are available then.

> Perhaps you can tell me a second thing. In section 7.5.2 they say
> there are 0-length packets used for frame-sync. I have never seen
> a 0-length packet coming from the interface, but some packets are
> (irregulary) shorter. Is the FreeBSD ugen-driver supporting 0-length
> packets?

Now that, I'm not sure of. :)

But if their device does that, which is USB 1.1 compliant, it's probably in 
the spec and so probably supported by ugen. Probably, there's only one real 
way to find out. ;)

-- 
Cheers,
Jay

http://www.evilrealms.net/ - Systems Administrator & Developer
http://www.imperial.ac.uk/ - 3rd year CS student
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