From: Dan Cross <cross@math.psu.edu>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] USB weirdness.
Date: Wed, 15 Jan 2003 17:00:15 -0500 [thread overview]
Message-ID: <200301152200.h0FM0Fw21426@augusta.math.psu.edu> (raw)
In-Reply-To: Your message of "Wed, 15 Jan 2003 21:33:45 GMT." <HOEHIDJJJINMLFPOLFJCKEKACJAA.nigel@9fs.org>
> No, that's quite likely. If the device class of the device descriptor
> is set to 0, so will be the subclass, and most likely the protocol. It
> indicates that the real information is within the configuration.
>
> As it says in Table 9-7 of USB 1,1:
>
> If this field is reset to zero, each interface
> within a configuration specifies its own
> class information and the various
> interfaces operate independently.
>
> Configurations represent different operating modes of a device; this
> is often used to have a device which has behaviour according to the
> standard, and a proprietary mode as well. Quite a lot of proprietary
> devices pass the buck to the configuration descriptor.
Okay, that makes sense, I guess.
> Unfortunately, the Plan 9 arrangements don't express alternate
> configurations.
Bummer. So does this mean I'll have to open every device that's
``Enabled 0x000000'' and probe the configuration to find the device
I'm looking for? Hmm.... Okay.
- Dan C.
prev parent reply other threads:[~2003-01-15 22:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-15 21:11 Dan Cross
2003-01-15 21:33 ` Nigel Roles
2003-01-15 22:00 ` Dan Cross [this message]
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