USB_BUFFER_MAP

Section: USB Core APIs (9)
Updated: February 2011
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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

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.  

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