Re: Requesting for less than endpoint size in UsbBuildInterruptOrBulkTransferRequest

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If you KNOW that the device will send less data, you CAN request less that
endpoint max packet size. If the device sends more than your buffer size,
the transfer fails, the endpoint is stalled.

"Abhijit Mmirajkar" <abhijit.mirajkar@xxxxxxxxx> wrote in message
news:1137662906.627235.155570@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Hi,
>
> For some reason I want to submit a read request with a buffer length of
> 128 which is less than the BULK-IN endpoint size (512 bytes).
> When I put the TransferBufferLength as 128 in
> UsbBuildInterruptOrBulkTransferRequest and issued the request to host
> controller driver, it never returned back to me !
>
> I saw on the USB bus analyzer that the device responded with 512 bytes
> of data, but the host did not give any ACK (nor NAK) for it, and
> stopped issuing any further bulk INs.
>
> I was curious to know whethere there is any such restriction that if a
> client driver should issue a bulk request of at least endpoint size ?
> It is not documented anywhere it seems.
> Thanks,
>
> Regards,
> Abhijit
>


.

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