//*****************************************************************************
//
// Handles USB_EVENT_REQUEST_BUFFER for a receive buffer.
//
// \param psBuffer points to the buffer which is receiving the event.
// \param ui32Size is the size of the buffer requested.
// \param ppui8Buffer is a pointer which is to be written with a pointer to
// the returned buffer.
//
// This function is called by a low level driver that wishes to receive data
// automatically and write it directly to a memory buffer, either using
// software or DMA prior to issuing USB_EVENT_RX_AVAILABLE. The event is sent
// in advance of receiving data to provide storage for whatever is received
// next.
//
// If we have a contiguous block of space in the buffer of at least ui32Size
// bytes immediately in front of the current write pointer, we pass this back
// otherwise we send NULL indicating that the next packet should be notified
// using a standard USB_EVENT_RX_AVAILABLE event without being received
// automatically. Note that the USB_EVENT_REQUEST_BUFFER protocol allows us to
// return less than \e ui32Size bytes if we know how much data is expected next
// but this is not possible here since the USBBuffer knows nothing about the
// protocol whose data it is handling.
//
// \return Returns the number of bytes remaining to be processed.
//
//*****************************************************************************
static uint32_t
HandleRequestBuffer(tUSBBuffer *psBuffer, uint32_t ui32Size,
uint8_t **ppui8Buffer)
{
uint32_t ui32Space;
//
// How much contiguous space do we have available?
//
ui32Space = USBRingBufContigFree(&psBuffer->sPrivateData.sRingBuf);
//
// Is there enough space available to satisfy the request?
//
if(ui32Space >= ui32Size)
{
//
// Yes - return the current write pointer
//
*ppui8Buffer = psBuffer->sPrivateData.sRingBuf.pui8Buf +
psBuffer->sPrivateData.sRingBuf.ui32WriteIndex;
return(ui32Size);
}
else
{
//
// We do not have enough contiguous space following the current write
// pointer to satisfy the request so do not provide a buffer.
//
*ppui8Buffer = (uint8_t *)0;
return(0);
}
}
//*****************************************************************************
//
// Handles USB_EVENT_REQUEST_BUFFER for a receive buffer.
//
// \param psBuffer points to the buffer which is receiving the event.
// \param ulSize is the size of the buffer requested.
// \param ppucBuffer is a pointer which is to be written with a pointer to
// the returned buffer.
//
// This function is called by a low level driver that wishes to receive data
// automatically and write it directly to a memory buffer, either using
// software or DMA prior to issuing USB_EVENT_RX_AVAILABLE. The event is sent
// in advance of receiving data to provide storage for whatever is received
// next.
//
// If we have a contiguous block of space in the buffer of at least ulSize
// bytes immediately in front of the current write pointer, we pass this back
// otherwise we send NULL indicating that the next packet should be notified
// using a standard USB_EVENT_RX_AVAILABLE event without being received
// automatically. Note that the USB_EVENT_REQUEST_BUFFER protocol allows us to
// return less than \e ulSize bytes if we know how much data is expected next
// but this is not possible here since the USBBuffer knows nothing about the
// protocol whose data it is handling.
//
// \return Returns the number of bytes remaining to be processed.
//
//*****************************************************************************
static unsigned long
HandleRequestBuffer(tUSBBuffer *psBuffer, unsigned long ulSize,
unsigned char **ppucBuffer)
{
tUSBBufferVars *psVars;
unsigned long ulSpace;
//
// Get a pointer to our workspace variables.
//
psVars = psBuffer->pvWorkspace;
//
// How much contiguous space do we have available?
//
ulSpace = USBRingBufContigFree(&psVars->sRingBuf);
//
// Is there enough space available to satisfy the request?
//
if(ulSpace >= ulSize)
{
//
// Yes - return the current write pointer
//
*ppucBuffer = psVars->sRingBuf.pucBuf + psVars->sRingBuf.ulWriteIndex;
return(ulSize);
}
else
{
//
// We do not have enough contiguous space following the current write
// pointer to satisfy the request so do not provide a buffer.
//
*ppucBuffer = (unsigned char *)0;
return(0);
}
}
//*****************************************************************************
//
// Handles USB_EVENT_RX_AVAILABLE for a receive buffer.
//
// \param psBuffer points to the buffer which is receiving the event.
// \param ulSize is the size reported in the event.
// \param pucData is the pointer provided in the event.
//
// This function is responsible for reading data from the lower layer into
// the buffer or, if we had previously passed a section of the buffer to the
// lower layer for it to write into directly, updating the buffer write pointer
// to add the new data to the buffer.
//
// If the pointer provided is NULL, we call the low level pfnTransfer function
// to get the new data. If the pointer is not NULL and not within the existing
// ring buffer, we copy the data directly from the pointer to the buffer and
// return the number of bytes read.
//
// \return Returns the number of bytes read from the lower layer.
//
//*****************************************************************************
static unsigned long
HandleRxAvailable(tUSBBuffer *psBuffer, unsigned long ulSize,
unsigned char *pucData)
{
tUSBBufferVars *psVars;
unsigned long ulAvail, ulRead, ulPacket, ulRetCount;
//
// Get a pointer to our workspace variables.
//
psVars = psBuffer->pvWorkspace;
//
// Has the data already been read into memory?
//
if(pucData)
{
//
// Yes - is it already in our ring buffer?
//
if((pucData >= psBuffer->pcBuffer) &&
(pucData < psBuffer->pcBuffer + psBuffer->ulBufferSize))
{
//
// The data is already in our ring buffer so merely update the
// write pointer to add the new data.
//
USBRingBufAdvanceWrite(&psVars->sRingBuf, ulSize);
//
// In this case, we pass back 0 to indicate that the lower layer
// doesn't need to make any buffer pointer updates.
//
ulRetCount = 0;
}
else
{
//
// The data is not within our buffer so we need to copy it into
// the buffer.
//
// How much space does the buffer have available?
//
ulAvail = USBRingBufFree(&psVars->sRingBuf);
//
// How much should we copy?
//
ulRead = (ulAvail < ulSize) ? ulAvail : ulSize;
//
// Copy the data into the buffer.
//
USBRingBufWrite(&psVars->sRingBuf, pucData, ulRead);
//
// We need to return the number of bytes we read in this case
// since the buffer supplied to us was owned by the lower layer and
// it may need to update its read pointer.
//
ulRetCount = ulRead;
}
}
else
{
//
// We were passed a NULL pointer so the low level driver has not read
// the data into memory yet. We need to call the transfer function to
// get the packet.
//
// How big is the packet that we need to receive?
//
ulPacket = psBuffer->pfnAvailable(psBuffer->pvHandle);
//
// How much contiguous space do we have in the buffer?
//
ulAvail = USBRingBufContigFree(&psVars->sRingBuf);
//
// Get as much of the packet as we can in the available space.
//
ulRead = psBuffer->pfnTransfer(psBuffer->pvHandle,
(psVars->sRingBuf.pucBuf +
psVars->sRingBuf.ulWriteIndex),
ulAvail, true);
//
// Advance the ring buffer write pointer to add our new data.
//
if(ulRead)
{
USBRingBufAdvanceWrite(&psVars->sRingBuf, ulRead);
}
//
// Did we get the whole packet?
//
if(ulRead < ulPacket)
{
//
// No - how much space do we have in the buffer?
//
ulAvail = USBRingBufContigFree(&psVars->sRingBuf);
//
// If there is any space left, read as much of the remainder of
// the packet as we can.
//
if(ulAvail)
{
ulPacket =
psBuffer->pfnTransfer(psBuffer->pvHandle,
(psVars->sRingBuf.pucBuf +
psVars->sRingBuf.ulWriteIndex),
ulAvail, true);
//
// Update the write pointer after we read more data into the
// buffer.
//
if(ulPacket)
{
USBRingBufAdvanceWrite(&psVars->sRingBuf, ulPacket);
}
}
}
//
// We need to return 0 in this case to indicate that the lower layer
// need not perform any buffer maintenance as a result of the callback.
//
ulRetCount = 0;
}
//
// How much data do we have in the buffer?
//
ulAvail = USBRingBufUsed(&psVars->sRingBuf);
//
// Pass the event on to the client with the current read pointer and
// available data size. The client is expected to understand the ring
// structure and be able to deal with wrap if it wants to read the data
// directly from the buffer.
//
ulRead = psBuffer->pfnCallback(psBuffer->pvCBData,
USB_EVENT_RX_AVAILABLE,
ulAvail,
(psVars->sRingBuf.pucBuf +
psVars->sRingBuf.ulReadIndex));
//
// If the client read anything from the buffer, update the read pointer.
//
USBRingBufAdvanceRead(&psVars->sRingBuf, ulRead);
//
// Return the correct value to the low level driver.
//
return(ulRetCount);
}
