On Dec 12, 2016, at 6:11 PM, Scott Deandrea <sdeand...@apple.com> wrote:
> I decided to implement isochronous transfers today and changed the structure
> slightly:
> struct
> {
> // Control information
> uint32_t frameHeaderLength; // 28
>
> // Frame information
> uint32_t frameLength; // Amount of data sent/received this frame
> uint32_t frameStatus; // IOReturn result of the I/O this frame
> uint64_t frameNumber; // Frame number on which this was scheduled/executed
> by the controller
> uint64_t ioTimestamp; // Time in which the frame completed
> } __attribute__((packed, aligned (sizeof(uint32_t))));
>
> Therefore, the isochronous format for a request with type
> kAppleUSBHostPacketFilterRequestComplete is as follows:
> Link Header
> padding, if required to force 4-byte alignment
> Isochronous Frame[0] Header (frameHeaderLength bytes in length)
> Isochronous Frame[0] Data (frameLength bytes)
> …
> padding, if required to force 4-byte alignment
> Isochronous Frame[linkHeader.ioFrameCount - 1] Header (aligned to 4 bytes,
> frameHeaderLength bytes in length)
> Isochronous Frame[linkHeader.ioFrameCount - 1] Data (frameLength bytes)
>
> The isochronous format for a request with type
> kAppleUSBHostPacketFilterRequestSubmit is similar (no data following the
> isochronous frame header):
> Link Header
> padding, if required to force 4-byte alignment
> Isochronous Frame[0] Header (frameHeaderLength bytes in length)
> …
> padding, if required to force 4-byte alignment
> Isochronous Frame[linkHeader.ioFrameCount - 1] Header (aligned to 4 bytes,
> frameHeaderLength bytes in length)
So, for a "submit" request, the frameStatus fields are presumably not
meaningful, as they reports the status of the completed transfer, right?
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