usb_buffer_map (9) - Linux Manuals

usb_buffer_map: create DMA mapping(s) for an urb

NAME

usb_buffer_map - create DMA mapping(s) for an urb

SYNOPSIS

struct urb * usb_buffer_map(struct urb * urb);

ARGUMENTS

urb

urb whose transfer_buffer/setup_packet will be mapped

DESCRIPTION

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.

RETURN

Either NULL (indicating no buffer could be mapped), or urb.

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