'\" t
.\"     Title: usb_sg_init
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: USB Core APIs
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "USB_SG_INIT" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "USB Core APIs"
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.SH "NAME"
usb_sg_init \- initializes scatterlist\-based bulk/interrupt I/O request
.SH "SYNOPSIS"
.HP \w'int\ usb_sg_init('u
.BI "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" ");"
.SH "ARGUMENTS"
.PP
\fIio\fR
.RS 4
request block being initialized\&. until
\fBusb_sg_wait\fR
returns, treat this as a pointer to an opaque block of memory,
.RE
.PP
\fIdev\fR
.RS 4
the usb device that will send or receive the data
.RE
.PP
\fIpipe\fR
.RS 4
endpoint
\(lqpipe\(rq
used to transfer the data
.RE
.PP
\fIperiod\fR
.RS 4
polling rate for interrupt endpoints, in frames or (for high speed endpoints) microframes; ignored for bulk
.RE
.PP
\fIsg\fR
.RS 4
scatterlist entries
.RE
.PP
\fInents\fR
.RS 4
how many entries in the scatterlist
.RE
.PP
\fIlength\fR
.RS 4
how many bytes to send from the scatterlist, or zero to send every byte identified in the list\&.
.RE
.PP
\fImem_flags\fR
.RS 4
SLAB_* flags affecting memory allocations in this call
.RE
.SH "DESCRIPTION"
.PP
This initializes a scatter/gather request, allocating resources such as I/O mappings and urb memory (except maybe memory used by USB controller drivers)\&.
.PP
The request must be issued using
\fBusb_sg_wait\fR, which waits for the I/O to complete (or to be canceled) and then cleans up all resources allocated by
\fBusb_sg_init\fR\&.
.PP
The request may be canceled with
\fBusb_sg_cancel\fR, either before or after
\fBusb_sg_wait\fR
is called\&.
.SH "RETURN"
.PP
Zero for success, else a negative errno value\&.
.SH "COPYRIGHT"
.br