diff -r 578be2adaf3e -r 307f4279f433 Adaptation/GUID-6E89E787-749D-5AC5-957D-967B4B9ACD74.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Adaptation/GUID-6E89E787-749D-5AC5-957D-967B4B9ACD74.dita Fri Oct 15 14:32:18 2010 +0100 @@ -0,0 +1,121 @@ + + + + + +Using +the BIL InterfaceThis tutorial describes how to use the Buffer Interface Layer (BIL) +to read and write shared chunks form the client driver. +

The BIL +is a thin layer over the LDD APIs that removes the need for the class driver +to handle buffers directly. The BIL is consistent between different class +drivers and reduces the buffer related understanding needed to use the USBSc +LDD.

Using the BIL is optional to the class driver, but very highly +recommended.

Before completing these steps you must have followed +the procedure from + the beginning of the tutorial set through to +RDevUsbcScClient::FinalizeInterface()

 + + Open each endpoint +object. + +Use the function RDevUsbcScClient::OpenEndpoint() for +each endpoint object. +TEndpointBuffer iEpBuf; +const TUint KWriteEp = 1; + +gPort.OpenEndpoint(iEpBuf, KWriteEp); + OpenEndpoint() fills the provided endpoint buffer +(iEpBuf) for use with the given endpoint number (KWriteEp). +This endpoint will be opened on the current alternate interface setting. + + + Reading with an OUT endpoint. +To read with an endpoint call TEndpointBuffer::GetBuffer() to +request data from the BIL. +r = iEpBuf.GetBuffer(scReadData, readSize, readZlp, aStatus); +The first parameter passed to GetBuffer() can be either +a pointer to the transfer buffer or the offset of the transfer data within +the shared chunk. +This function allows the BIL to expire any previously retrieved transfer +on this endpoint so that it can be used again for new transfers. If the transfer +or the LDD are not ready then aStatus is set to pending. +If no transfer is available then the variable passed in the first parameter +is set to NULL or 0 depending on the API. Call this function again on completion, +to wait for data again. +The function GetBuffer() returns: + + + + KErrCompletion if data could be retrieved without +a pending request, + + + KErrNone if an asynchronous request was queued. This +function should be called again on completion, + + + KErrEof if the end of the data in the endpoint has +been reached, + + + KErrNotSupported if the endpoint is an IN endpoint. + + +If the host has changed to an alternate setting and you wish to continue +reading and writing data then you must Close() all endpoints +and go to step five Process the next alternate set of endpoints. Otherwise, +if you have finished then go to step four Close each endpoint object. + + + Writing with an IN endpoint. +After filling a shared chunk buffer with some data call TEndpointBuffer::WriteBuffer() to +write the data to endpoint hardware. + WriteBuffer() transmits the provided buffer on the +given endpoint asynchronously. More than one request may be outstanding at +any time. This reduces the time between buffer transfers. +r = iEpBuf.WriteBuffer(buffer, length, ETrue, aStatus); +The first parameter passed to WriteBuffer() can be +either a pointer to the transfer buffer or the offset of the transfer data +within the shared chunk. +If the host has changed to an alternate setting and you wish to continue +reading and writing data then you must Close() all endpoints +and go to step five Process the next alternate set of endpoints. Otherwise, +if you have finished then go to step four Close each endpoint object. + + + Close each endpoint object. +Each endpoint object opened with OpenEndpoint() must +be closed with TEndpointBuffer::Close(). +iEpBuf.Close(); +If the host has changed to an alternate setting and you wish to continue +reading and writing data then you must Close() all endpoints +and go to step five Process the next alternate set of endpoints. Otherwise, +if you have finished data transfer then Close +and Unload the Driver. +If you wish to continue reading and writing data but on an alternate +setting then call RDevUsbcScClient::StartNextOutAlternateSetting(). +Otherwise if you have finished then Close and Unload the Driver. + + + Process the next alternate set of endpoints. +Use the function RDevUsbcScClient::StartNextOutAlternateSetting() to +switch to the next set of endpoints. The alternate interfaces were initialised +with SetInterface(). See Set +the Interface Descriptors. +TInt r = StartNextOutAlternateSetting(ETrue); +Pass ETrue to the function to purge the buffers of any data unread for +the previous setting. + Note: All open endpoints (except EP0) must be closed before this is +called. + + +

When you have finished reading and writing Close +and Unload the Driver.

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