Initializes scatterlist-based bulk/interrupt i/o request
int usb_sg_init(struct usb_sg_request * io, struct usb_device * dev, unsigned pipe, unsigned period, struct scatterlist * sg, int nents, size_t length, gfp_t mem_flags);
io
request block being initialized. until usb_sg_wait returns, treat this as a pointer to an opaque block of memory,
dev
the usb device that will send or receive the data
pipe
endpoint “pipe” used to transfer the data
period
polling rate for interrupt endpoints, in frames or (for high speed endpoints) microframes; ignored for bulk
sg
scatterlist entries
nents
how many entries in the scatterlist
length
how many bytes to send from the scatterlist, or zero to send every byte identified in the list.
mem_flags
SLAB_* flags affecting memory allocations in this call
This initializes a scatter/gather request, allocating resources such as I/O mappings and urb memory (except maybe memory used by USB controller drivers).
The request must be issued using usb_sg_wait, which waits for the I/O to complete (or to be canceled) and then cleans up all resources allocated by usb_sg_init.
The request may be canceled with usb_sg_cancel, either before or after usb_sg_wait is called.
Zero for success, else a negative errno value.