SPANS_BOUNDARY(9) Internal Functions SPANS_BOUNDARY(9)NAME
spans_boundary - Check a packet can be ISA DMA'd
SYNOPSIS
int spans_boundary(struct sk_buff * skb);
ARGUMENTS
skb
The buffer to check
DESCRIPTION
Returns true if the buffer cross a DMA boundary on a PC. The poor thing can only DMA within a 64K block not across the edges of it.
AUTHOR
Alan Cox <alan@lxorguk.ukuu.org.uk>
Author.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 SPANS_BOUNDARY(9)
Check Out this Related Man Page
USB_BUFFER_MAP_SG(9) USB Core APIs USB_BUFFER_MAP_SG(9)NAME
usb_buffer_map_sg - create scatterlist DMA mapping(s) for an endpoint
SYNOPSIS
int usb_buffer_map_sg(const struct usb_device * dev, int is_in, struct scatterlist * sg, int nents);
ARGUMENTS
dev
device to which the scatterlist will be mapped
is_in
mapping transfer direction
sg
the scatterlist to map
nents
the number of entries in the scatterlist
RETURN
Either < 0 (indicating no buffers could be mapped), or the number of DMA mapping array entries in the scatterlist.
NOTE
The caller is responsible for placing the resulting DMA addresses from the scatterlist into URB transfer buffer pointers, and for setting
the URB_NO_TRANSFER_DMA_MAP transfer flag in each of those URBs.
Top I/O rates come from queuing URBs, instead of waiting for each one to complete before starting the next I/O. This is particularly easy
to do with scatterlists. Just allocate and submit one URB for each DMA mapping entry returned, stopping on the first error or when all
succeed. Better yet, use the usb_sg_*() calls, which do that (and more) for you.
This call would normally be used when translating scatterlist requests, rather than usb_buffer_map, since on some hardware (with IOMMUs) it
may be able to coalesce mappings for improved I/O efficiency.
Reverse the effect of this call with usb_buffer_unmap_sg.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 USB_BUFFER_MAP_SG(9)
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