usbport and zero length packet

Question

Hi,

In the USB 2.0 (5.6.4) spec written: 

"An isochronous IN endpoint must return a zero-length packet whenever data is requested at a faster interval
than the specified interval and data is not available."

The question: 

In case of zero-length packet received from the device, would the usbport driver try to receive the same packet again, or there would be a "hole" in the client URB buffer?

Answer 1

Yuri D wrote:

>

>In the USB 2.0 (5.6.4) spec written: 

>

>"An isochronous IN endpoint must return a zero-length packet whenever

>data is requested at a faster interval than the specified interval

>and data is not available."

>

>The question: 

>

>In case of zero-length packet received from the device, would the

>usbport driver try to receive the same packet again, or there

>would be a "hole" in the client URB buffer?

 

There will be a hole.  Each packet in an isochronous URB corresponds

exactly to one scheduling interval.  If your device misses one, the packet

will contain 0 bytes and an error code.

--

Tim Roberts, [e-mail]

Providenza & Boekelheide, Inc.

 

---

Tim Roberts, VC++ MVP Providenza & Boekelheide, Inc.

Answer 2

Tim,

Thanks a lot for an answer!