'\" t
.\"     Title: usb_get_descriptor
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: USB Core APIs
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "USB_GET_DESCRIPTOR" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "USB Core APIs"
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.SH "NAME"
usb_get_descriptor \- issues a generic GET_DESCRIPTOR request
.SH "SYNOPSIS"
.HP \w'int\ usb_get_descriptor('u
.BI "int usb_get_descriptor(struct\ usb_device\ *\ " "dev" ", unsigned\ char\ " "type" ", unsigned\ char\ " "index" ", void\ *\ " "buf" ", int\ " "size" ");"
.SH "ARGUMENTS"
.PP
\fIdev\fR
.RS 4
the device whose descriptor is being retrieved
.RE
.PP
\fItype\fR
.RS 4
the descriptor type (USB_DT_*)
.RE
.PP
\fIindex\fR
.RS 4
the number of the descriptor
.RE
.PP
\fIbuf\fR
.RS 4
where to put the descriptor
.RE
.PP
\fIsize\fR
.RS 4
how big is
\(lqbuf\(rq?
.RE
.SH "CONTEXT"
.PP
!in_interrupt ()
.SH "DESCRIPTION"
.PP
Gets a USB descriptor\&. Convenience functions exist to simplify getting some types of descriptors\&. Use
\fBusb_get_string\fR
or
\fBusb_string\fR
for USB_DT_STRING\&. Device (USB_DT_DEVICE) and configuration descriptors (USB_DT_CONFIG) are part of the device structure\&. In addition to a number of USB\-standard descriptors, some devices also use class\-specific or vendor\-specific descriptors\&.
.PP
This call is synchronous, and may not be used in an interrupt context\&.
.SH "RETURN"
.PP
The number of bytes received on success, or else the status code returned by the underlying
\fBusb_control_msg\fR
call\&.
.SH "COPYRIGHT"
.br