Re: DLT_ request

[Scott Deandrea <sdeandrea () apple com>]

Hi,

The bcdVersion field is interpreted as described by the bcdUSB field of the standard device descriptor in section 9.6.1:
The bcdUSB field contains a BCD version number. The value of the bcdUSB field is 0xJJMN for version JJ.M.N (JJ – major 
version number, M – minor version number, N – sub-minor version number), e.g., version 2.1.3 is represented with value 
0x0213 and version 2.0 is represented with a value of 0x0200.

Yes, for every USB request issued by the host there’s a kAppleUSBHostPacketFilterRequestSubmit packet emitted at 
request time and a kAppleUSBHostPacketFilterRequestComplete packet emitted when the request completes with the same 
ioID value.  For control endpoints, the submit packet also contains the setup data.  For all other endpoint types, the 
submit packet is only this header.  The complete packet contains any data that was transferred.

—scott


> On Dec 10, 2016, at 6:48 PM, Guy Harris <guy () alum mit edu> wrote:
>
> On Dec 9, 2016, at 6:40 PM, Scott Deandrea <sdeandrea () apple com> wrote:
>
> > For the initial release I’m planning to use 0x0100 for the bcdVersion. 
>
> So I'm guessing "bcd" implies that either octets or nibbles represent digits; is that the case?
>
> > tAppleUSBHostPacketFilterRequestType doesn’t exist in public domain at this point.  It tracks when a request was 
> > enqueued and when it completed and it is defined as follows:
> > enum tAppleUSBHostPacketFilterRequestType
> > {
> >   kAppleUSBHostPacketFilterRequestSubmit   = 0,
> >   kAppleUSBHostPacketFilterRequestComplete = 1
> > };
>
> So does that mean that, for every USB request issued by the host, there's a kAppleUSBHostPacketFilterRequestSubmit 
> packet emitted at request time and a kAppleUSBHostPacketFilterRequestComplete packet emitted when the request is 
> complete, with the same ioID value, and with each request getting its own ioID value (unless the system has been up 
> long enough to make more than 2^32 USB requests...)?
>
> > The additional information is indeed expected to increase the header length and bcdVersion should it ever be 
> > required.
>
> So if the bcdVersion is 0x0100, the length should always be 32?
>
> > Correct, the captured data would be the data field of a usb packet as described in section 8.3.4.
>
> So is there a way to determine whether the payload begins with Setup data?  Would that be the case for all submitted 
> requests with an endpointType of kEndpointTypeControl (0) and an endpointAddress with an endpoint number of 0 
> (Default Control Pipe)?

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