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Hi, Marc
Thx for your kindly help :-)
My question should be :  Is it possible to use SetDescriptor Request (but not GetDescriptor) to modify the Interface Descriptor. ? or is it recommended to do so ?
Here "modify" means to modify the content of an interface descriptor, e.g., bNumEndpoints field .

Another problem: According to the USB2.0 spec, only 1 device is in presence. But what's the factual situation?  What's the general solution? Do we need multiple device descriptors in case of OTG development, where CBI/Bulk Only/Still Image/etc. Class are all potential devices? Alllowing the Application Software to implement multiple Device Descriptors and select an approximate one to respond to the host ? or 1 single Device Descriptor with multiple Configuration/Interface Descriptors ?

Best Rgds,
-------------------------------
Joe

----- Original Message ----- 
From: "Marc Reinig" <mreinig@p...>
To: "Discussion list about free,open source USB IP core" <usb@o...>
Sent: Saturday, February 07, 2004 12:02 AM
Subject: RE: [usb] Help about 

> 
> Interface descriptors are transferred as part of the configuration
> descriptor.  GetDescriptor(configuration) is the way.
> 
> What do you mean "modify" the interface descriptor?
> 
> Set_Interface allows the host to select from alternate interfaces, if they
> exist, for a given configuration.  It is an optional command.
> 
> http://www.semiconductors.philips.com/acrobat/usermanuals/UM10028_1.pdf
> 
> might help for how to connect it.
> 
> Marc Reinig
> System Solutions
> Windows Driver and Embedded Product Consulting
> 
> > -----Original Message-----
> > From: usb-bounces@o...
> > [mailto:usb-bounces@o...]On Behalf Of Lifeng Chen
> > Sent: Thursday, February 05, 2004 7:45 PM
> > To: Discussion list about free,open source USB IP core
> > Subject: [usb] Help about
> >
> >
> > Hi all,
> > Can anyone help me out with these questions:
> >
> > 1. It's said in the USB2.0 spec section 9.6.5 (P267)
> > that,"Interface descriptors cannot be directly accessed with a
> > GetDescriptor() or SetDescriptor() request." So my question is:
> > can I access them indirectly? and how?
> >
> > e.g. if I wanna modify an Interface descriptor, call the
> > GetDescriptor() ? give me some details pls.
> >
> > 2.I'm developing an OTG device. which will interface USB bus via
> > philips ISP1301. However I can't find the datasheet at philips
> > website or anywhere else. Anyone has idea about the I2C
> > transceiver interface? and send me a copy of the datasheet?
> >
> >
> > many thx
> >
> >
> > Joe
> >
> > Feb 6th.
> >
> > _______________________________________________
> > http://www.opencores.org/mailman/listinfo/usb
> _______________________________________________
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