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Date: Tue, 13 Sep 2011 21:14:28 +0200
From: =?ISO-8859-15?Q?Frank_Sch=E4fer?= <fschaefer.oss@googlemail.com>
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To: Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: Question about USB interface index restriction in gspca
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Hi,

I have a question about the following code in gspca.c:

in function gspca_dev_probe(...):
     ...
     /* the USB video interface must be the first one */
     if (dev->config->desc.bNumInterfaces != 1
&& intf->cur_altsetting->desc.bInterfaceNumber != 0)
             return -ENODEV;
     ...


Is there a special reason for not allowing devices with USB interface 
index > 0 for video ?
I'm experimenting with a device that has the video interface at index 3 
and two audio interfaces at index 0 and 1 (index two is missing !).
And the follow-up question: can we assume that all device handled by the 
gspca-driver have vendor specific video interfaces ?
Then we could change the code to

     ...
     /* the USB video interface must be of class vendor */
     if (intf->cur_altsetting->desc.bInterfaceClass != 
USB_CLASS_VENDOR_SPEC)
             return -ENODEV;
      ...

Regards,
Frank