USB_SG_INIT(9)                            USB Core APIs                            USB_SG_INIT(9)



NAME
       usb_sg_init - initializes scatterlist-based bulk/interrupt I/O request

SYNOPSIS
       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);

ARGUMENTS
       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

DESCRIPTION
       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.

RETURN
       Zero for success, else a negative errno value.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                            USB_SG_INIT(9)