<toc></toc>
-<chapter><title>Introduction</title>
+<chapter id="intro"><title>Introduction</title>
<para>This document presents a Linux-USB "Gadget"
kernel mode
<para>This is the lowest software level.
It is the only layer that talks to hardware,
through registers, fifos, dma, irqs, and the like.
- The <filename><linux/usb_gadget.h></filename> API abstracts
+ The <filename><linux/usb/gadget.h></filename> API abstracts
the peripheral controller endpoint hardware.
That hardware is exposed through endpoint objects, which accept
streams of IN/OUT buffers, and through callbacks that interact
<sect1 id="core"><title>Core Objects and Methods</title>
<para>These are declared in
-<filename><linux/usb_gadget.h></filename>,
+<filename><linux/usb/gadget.h></filename>,
and are used by gadget drivers to interact with
USB peripheral controller drivers.
</para>
unless the explanations are trivial.
-->
-!Iinclude/linux/usb_gadget.h
+!Iinclude/linux/usb/gadget.h
</sect1>
<sect1 id="utils"><title>Optional Utilities</title>
<!-- !Edrivers/usb/gadget/epautoconf.c -->
</sect1>
+<sect1 id="composite"><title>Composite Device Framework</title>
+
+<para>The core API is sufficient for writing drivers for composite
+USB devices (with more than one function in a given configuration),
+and also multi-configuration devices (also more than one function,
+but not necessarily sharing a given configuration).
+There is however an optional framework which makes it easier to
+reuse and combine functions.
+</para>
+
+<para>Devices using this framework provide a <emphasis>struct
+usb_composite_driver</emphasis>, which in turn provides one or
+more <emphasis>struct usb_configuration</emphasis> instances.
+Each such configuration includes at least one
+<emphasis>struct usb_function</emphasis>, which packages a user
+visible role such as "network link" or "mass storage device".
+Management functions may also exist, such as "Device Firmware
+Upgrade".
+</para>
+
+!Iinclude/linux/usb/composite.h
+!Edrivers/usb/gadget/composite.c
+
+</sect1>
+
+<sect1 id="functions"><title>Composite Device Functions</title>
+
+<para>At this writing, a few of the current gadget drivers have
+been converted to this framework.
+Near-term plans include converting all of them, except for "gadgetfs".
+</para>
+
+!Edrivers/usb/gadget/f_acm.c
+!Edrivers/usb/gadget/f_serial.c
+
+</sect1>
+
+
</chapter>
<chapter id="controllers"><title>Peripheral Controller Drivers</title>