usb_buffer_map - create DMA mapping(s) for an urb
2. SYNOPSIS ▲
struct urb * usb_buffer_map(struct urb * urb );
3. ARGUMENTS ▲
urb whose transfer_buffer/setup_packet will be mapped
4. DESCRIPTION ▲
Return value is either null (indicating no buffer could be mapped), or the parameter. URB_NO_TRANSFER_DMA_MAP is added to urb->transfer_flags if the operation succeeds. If the device is connected to this system through a non-DMA controller, this operation always succeeds.
This call would normally be used for an urb which is reused, perhaps as the target of a large periodic transfer, with usb_buffer_dmasync calls to synchronize memory and dma state.
Reverse the effect of this call with usb_buffer_unmap.
5. COPYRIGHT ▲