usb gadget: composite gadget core

Add <linux/usb/composite.h> interfaces for composite gadget drivers, and
basic implementation support behind it:

  - struct usb_function ... groups one or more interfaces into a function
    managed as one unit within a configuration, to which it's added by
    usb_add_function().

  - struct usb_configuration ... groups one or more such functions into
    a configuration managed as one unit by a driver, to which it's added
    by usb_add_config().  These operate at either high or full/low speeds
    and at a given bMaxPower.

  - struct usb_composite_driver ... groups one or more such configurations
    into a gadget driver, which may be registered or unregistered.

  - struct usb_composite_dev ... a usb_composite_driver manages this; it
    wraps the usb_gadget exposed by the controller driver.

This also includes some basic kerneldoc.

How to use it (the short version):  provide a usb_composite_driver with a
bind() that calls usb_add_config() for each of the needed configurations.
The configurations in turn have bind() calls, which will usb_add_function()
for each function required.  Each function's bind() allocates resources
needed to perform its tasks, like endpoints; sometimes configurations will
allocate resources too.

Separate patches will convert most gadget drivers to this infrastructure.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Documentation/DocBook/gadget.tmpl

@@ -524,6 +524,41 @@ These utilities include endpoint autoconfiguration.
 <!-- !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>
+
+</sect1>
+
+
 </chapter>
 
 <chapter id="controllers"><title>Peripheral Controller Drivers</title>

include/linux/usb/composite.h

+/*
+ * composite.h -- framework for usb gadgets which are composite devices
+ *
+ * Copyright (C) 2006-2008 David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef	__LINUX_USB_COMPOSITE_H
+#define	__LINUX_USB_COMPOSITE_H
+
+/*
+ * This framework is an optional layer on top of the USB Gadget interface,
+ * making it easier to build (a) Composite devices, supporting multiple
+ * functions within any single configuration, and (b) Multi-configuration
+ * devices, also supporting multiple functions but without necessarily
+ * having more than one function per configuration.
+ *
+ * Example:  a device with a single configuration supporting both network
+ * link and mass storage functions is a composite device.  Those functions
+ * might alternatively be packaged in individual configurations, but in
+ * the composite model the host can use both functions at the same time.
+ */
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+
+
+struct usb_configuration;
+
+/**
+ * struct usb_function - describes one function of a configuration
+ * @name: For diagnostics, identifies the function.
+ * @strings: tables of strings, keyed by identifiers assigned during bind()
+ *	and by language IDs provided in control requests
+ * @descriptors: Table of full (or low) speed descriptors, using interface and
+ *	string identifiers assigned during @bind().  If this pointer is null,
+ *	the function will not be available at full speed (or at low speed).
+ * @hs_descriptors: Table of high speed descriptors, using interface and
+ *	string identifiers assigned during @bind().  If this pointer is null,
+ *	the function will not be available at high speed.
+ * @config: assigned when @usb_add_function() is called; this is the
+ *	configuration with which this function is associated.
+ * @bind: Before the gadget can register, all of its functions bind() to the
+ *	available resources including string and interface identifiers used
+ *	in interface or class descriptors; endpoints; I/O buffers; and so on.
+ * @unbind: Reverses @bind; called as a side effect of unregistering the
+ *	driver which added this function.
+ * @set_alt: (REQUIRED) Reconfigures altsettings; function drivers may
+ *	initialize usb_ep.driver data at this time (when it is used).
+ *	Note that setting an interface to its current altsetting resets
+ *	interface state, and that all interfaces have a disabled state.
+ * @get_alt: Returns the active altsetting.  If this is not provided,
+ *	then only altsetting zero is supported.
+ * @disable: (REQUIRED) Indicates the function should be disabled.  Reasons
+ *	include host resetting or reconfiguring the gadget, and disconnection.
+ * @setup: Used for interface-specific control requests.
+ * @suspend: Notifies functions when the host stops sending USB traffic.
+ * @resume: Notifies functions when the host restarts USB traffic.
+ *
+ * A single USB function uses one or more interfaces, and should in most
+ * cases support operation at both full and high speeds.  Each function is
+ * associated by @usb_add_function() with a one configuration; that function
+ * causes @bind() to be called so resources can be allocated as part of
+ * setting up a gadget driver.  Those resources include endpoints, which
+ * should be allocated using @usb_ep_autoconfig().
+ *
+ * To support dual speed operation, a function driver provides descriptors
+ * for both high and full speed operation.  Except in rare cases that don't
+ * involve bulk endpoints, each speed needs different endpoint descriptors.
+ *
+ * Function drivers choose their own strategies for managing instance data.
+ * The simplest strategy just declares it "static', which means the function
+ * can only be activated once.  If the function needs to be exposed in more
+ * than one configuration at a given speed, it needs to support multiple
+ * usb_function structures (one for each configuration).
+ *
+ * A more complex strategy might encapsulate a @usb_function structure inside
+ * a driver-specific instance structure to allows multiple activations.  An
+ * example of multiple activations might be a CDC ACM function that supports
+ * two or more distinct instances within the same configuration, providing
+ * several independent logical data links to a USB host.
+ */
+struct usb_function {
+	const char			*name;
+	struct usb_gadget_strings	**strings;
+	struct usb_descriptor_header	**descriptors;
+	struct usb_descriptor_header	**hs_descriptors;
+
+	struct usb_configuration	*config;
+
+	/* REVISIT:  bind() functions can be marked __init, which
+	 * makes trouble for section mismatch analysis.  See if
+	 * we can't restructure things to avoid mismatching.
+	 * Related:  unbind() may kfree() but bind() won't...
+	 */
+
+	/* configuration management:  bind/unbind */
+	int			(*bind)(struct usb_configuration *,
+					struct usb_function *);
+	void			(*unbind)(struct usb_configuration *,
+					struct usb_function *);
+
+	/* runtime state management */
+	int			(*set_alt)(struct usb_function *,
+					unsigned interface, unsigned alt);
+	int			(*get_alt)(struct usb_function *,
+					unsigned interface);
+	void			(*disable)(struct usb_function *);
+	int			(*setup)(struct usb_function *,
+					const struct usb_ctrlrequest *);
+	void			(*suspend)(struct usb_function *);
+	void			(*resume)(struct usb_function *);
+
+	/* internals */
+	struct list_head		list;
+};
+
+int usb_add_function(struct usb_configuration *, struct usb_function *);
+
+int usb_interface_id(struct usb_configuration *, struct usb_function *);
+
+/**
+ * ep_choose - select descriptor endpoint at current device speed
+ * @g: gadget, connected and running at some speed
+ * @hs: descriptor to use for high speed operation
+ * @fs: descriptor to use for full or low speed operation
+ */
+static inline struct usb_endpoint_descriptor *
+ep_choose(struct usb_gadget *g, struct usb_endpoint_descriptor *hs,
+		struct usb_endpoint_descriptor *fs)
+{
+	if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
+		return hs;
+	return fs;
+}
+
+#define	MAX_CONFIG_INTERFACES		16	/* arbitrary; max 255 */
+
+/**
+ * struct usb_configuration - represents one gadget configuration
+ * @label: For diagnostics, describes the configuration.
+ * @strings: Tables of strings, keyed by identifiers assigned during @bind()
+ *	and by language IDs provided in control requests.
+ * @descriptors: Table of descriptors preceding all function descriptors.
+ *	Examples include OTG and vendor-specific descriptors.
+ * @bind: Called from @usb_add_config() to allocate resources unique to this
+ *	configuration and to call @usb_add_function() for each function used.
+ * @unbind: Reverses @bind; called as a side effect of unregistering the
+ *	driver which added this configuration.
+ * @setup: Used to delegate control requests that aren't handled by standard
+ *	device infrastructure or directed at a specific interface.
+ * @bConfigurationValue: Copied into configuration descriptor.
+ * @iConfiguration: Copied into configuration descriptor.
+ * @bmAttributes: Copied into configuration descriptor.
+ * @bMaxPower: Copied into configuration descriptor.
+ * @cdev: assigned by @usb_add_config() before calling @bind(); this is
+ *	the device associated with this configuration.
+ *
+ * Configurations are building blocks for gadget drivers structured around
+ * function drivers.  Simple USB gadgets require only one function and one
+ * configuration, and handle dual-speed hardware by always providing the same
+ * functionality.  Slightly more complex gadgets may have more than one
+ * single-function configuration at a given speed; or have configurations
+ * that only work at one speed.
+ *
+ * Composite devices are, by definition, ones with configurations which
+ * include more than one function.
+ *
+ * The lifecycle of a usb_configuration includes allocation, initialization
+ * of the fields described above, and calling @usb_add_config() to set up
+ * internal data and bind it to a specific device.  The configuration's
+ * @bind() method is then used to initialize all the functions and then
+ * call @usb_add_function() for them.
+ *
+ * Those functions would normally be independant of each other, but that's
+ * not mandatory.  CDC WMC devices are an example where functions often
+ * depend on other functions, with some functions subsidiary to others.
+ * Such interdependency may be managed in any way, so long as all of the
+ * descriptors complete by the time the composite driver returns from
+ * its bind() routine.
+ */
+struct usb_configuration {
+	const char			*label;
+	struct usb_gadget_strings	**strings;
+	const struct usb_descriptor_header **descriptors;
+
+	/* REVISIT:  bind() functions can be marked __init, which
+	 * makes trouble for section mismatch analysis.  See if
+	 * we can't restructure things to avoid mismatching...
+	 */
+
+	/* configuration management:  bind/unbind */
+	int			(*bind)(struct usb_configuration *);
+	void			(*unbind)(struct usb_configuration *);
+	int			(*setup)(struct usb_configuration *,
+					const struct usb_ctrlrequest *);
+
+	/* fields in the config descriptor */
+	u8			bConfigurationValue;
+	u8			iConfiguration;
+	u8			bmAttributes;
+	u8			bMaxPower;
+
+	struct usb_composite_dev	*cdev;
+
+	/* internals */
+	struct list_head	list;
+	struct list_head	functions;
+	u8			next_interface_id;
+	unsigned		highspeed:1;
+	unsigned		fullspeed:1;
+	struct usb_function	*interface[MAX_CONFIG_INTERFACES];
+};
+
+int usb_add_config(struct usb_composite_dev *,
+		struct usb_configuration *);
+
+/**
+ * struct usb_composite_driver - groups configurations into a gadget
+ * @name: For diagnostics, identifies the driver.
+ * @dev: Template descriptor for the device, including default device
+ *	identifiers.
+ * @strings: tables of strings, keyed by identifiers assigned during bind()
+ *	and language IDs provided in control requests
+ * @bind: (REQUIRED) Used to allocate resources that are shared across the
+ *	whole device, such as string IDs, and add its configurations using
+ *	@usb_add_config().  This may fail by returning a negative errno
+ *	value; it should return zero on successful initialization.
+ * @unbind: Reverses @bind(); called as a side effect of unregistering
+ *	this driver.
+ *
+ * Devices default to reporting self powered operation.  Devices which rely
+ * on bus powered operation should report this in their @bind() method.
+ *
+ * Before returning from @bind, various fields in the template descriptor
+ * may be overridden.  These include the idVendor/idProduct/bcdDevice values
+ * normally to bind the appropriate host side driver, and the three strings
+ * (iManufacturer, iProduct, iSerialNumber) normally used to provide user
+ * meaningful device identifiers.  (The strings will not be defined unless
+ * they are defined in @dev and @strings.)  The correct ep0 maxpacket size
+ * is also reported, as defined by the underlying controller driver.
+ */
+struct usb_composite_driver {
+	const char				*name;
+	const struct usb_device_descriptor	*dev;
+	struct usb_gadget_strings		**strings;
+
+	/* REVISIT:  bind() functions can be marked __init, which
+	 * makes trouble for section mismatch analysis.  See if
+	 * we can't restructure things to avoid mismatching...
+	 */
+
+	int			(*bind)(struct usb_composite_dev *);
+	int			(*unbind)(struct usb_composite_dev *);
+};
+
+extern int usb_composite_register(struct usb_composite_driver *);
+extern void usb_composite_unregister(struct usb_composite_driver *);
+
+
+/**
+ * struct usb_composite_device - represents one composite usb gadget
+ * @gadget: read-only, abstracts the gadget's usb peripheral controller
+ * @req: used for control responses; buffer is pre-allocated
+ * @bufsiz: size of buffer pre-allocated in @req
+ * @config: the currently active configuration
+ *
+ * One of these devices is allocated and initialized before the
+ * associated device driver's bind() is called.
+ *
+ * OPEN ISSUE:  it appears that some WUSB devices will need to be
+ * built by combining a normal (wired) gadget with a wireless one.
+ * This revision of the gadget framework should probably try to make
+ * sure doing that won't hurt too much.
+ *
+ * One notion for how to handle Wireless USB devices involves:
+ * (a) a second gadget here, discovery mechanism TBD, but likely
+ *     needing separate "register/unregister WUSB gadget" calls;
+ * (b) updates to usb_gadget to include flags "is it wireless",
+ *     "is it wired", plus (presumably in a wrapper structure)
+ *     bandgroup and PHY info;
+ * (c) presumably a wireless_ep wrapping a usb_ep, and reporting
+ *     wireless-specific parameters like maxburst and maxsequence;
+ * (d) configurations that are specific to wireless links;
+ * (e) function drivers that understand wireless configs and will
+ *     support wireless for (additional) function instances;
+ * (f) a function to support association setup (like CBAF), not
+ *     necessarily requiring a wireless adapter;
+ * (g) composite device setup that can create one or more wireless
+ *     configs, including appropriate association setup support;
+ * (h) more, TBD.
+ */
+struct usb_composite_dev {
+	struct usb_gadget		*gadget;
+	struct usb_request		*req;
+	unsigned			bufsiz;
+
+	struct usb_configuration	*config;
+
+	/* internals */
+	struct usb_device_descriptor	desc;
+	struct list_head		configs;
+	struct usb_composite_driver	*driver;
+	u8				next_string_id;
+
+	spinlock_t			lock;
+
+	/* REVISIT use and existence of lock ... */
+};
+
+extern int usb_string_id(struct usb_composite_dev *c);
+
+/* messaging utils */
+#define DBG(d, fmt, args...) \
+	dev_dbg(&(d)->gadget->dev , fmt , ## args)
+#define VDBG(d, fmt, args...) \
+	dev_vdbg(&(d)->gadget->dev , fmt , ## args)
+#define ERROR(d, fmt, args...) \
+	dev_err(&(d)->gadget->dev , fmt , ## args)
+#define WARN(d, fmt, args...) \
+	dev_warn(&(d)->gadget->dev , fmt , ## args)
+#define INFO(d, fmt, args...) \
+	dev_info(&(d)->gadget->dev , fmt , ## args)
+
+#endif	/* __LINUX_USB_COMPOSITE_H */