usb_sg_init — 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,
devthe usb device that will send or receive the data
pipeendpoint “pipe” used to transfer the data
periodpolling rate for interrupt endpoints, in frames or (for high speed endpoints) microframes; ignored for bulk
sgscatterlist entries
nentshow many entries in the scatterlist
lengthhow many bytes to send from the scatterlist, or zero to send every byte identified in the list.
mem_flagsSLAB_* flags affecting memory allocations in this call
Returns zero for success, else a negative errno value. 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.