USB: gmidi: New USB MIDI Gadget class driver.

This driver is glue between the USB gadget interface
and the ALSA MIDI interface. It allows us to appear
as a MIDI Streaming device to a host system on the
other end of a USB cable.

This includes linux/usb/audio.h and linux/usb/midi.h
containing definitions from the relevant USB specifications
for USB audio and USB MIDI devices.

The following changes have been made since the first RFC
posting:

* Bug fixes to endpoint handling.
* Workaround for USB_REQ_SET_CONFIGURATION handling,
  not understood yet.
* Added SND and SND_RAWMIDI dependencies in Kconfig.
* Moved usb_audio.h and usb_midi.h to usb/*.h
* Added module parameters for ALSA card index and id.
* Added module parameters for USB descriptor IDs and strings.
* Removed some unneeded stuff inherited from zero.c, more to go.
* Provide DECLARE_* macros for the variable-length structs.
* Use kmalloc instead of usb_ep_alloc_buffer.
* Limit source to 80 columns.
* Return actual error code instead of -ENOMEM in a few places.
Signed-off-by: Ben Williamson <ben.williamson@greyinnovation.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/Kconfig

@@ -404,6 +404,20 @@ config USB_G_SERIAL
 	  which includes instructions and a "driver info file" needed to
 	  make MS-Windows work with this driver.
 
+config USB_MIDI_GADGET
+	tristate "MIDI Gadget (EXPERIMENTAL)"
+	depends on SND && EXPERIMENTAL
+	select SND_RAWMIDI
+	help
+	  The MIDI Gadget acts as a USB Audio device, with one MIDI
+	  input and one MIDI output. These MIDI jacks appear as
+	  a sound "card" in the ALSA sound system. Other MIDI
+	  connections can then be made on the gadget system, using
+	  ALSA's aconnect utility etc.
+
+	  Say "y" to link the driver statically, or "m" to build a
+	  dynamically linked module called "g_midi".
+
 
 # put drivers that need isochronous transfer support (for audio
 # or video class gadget drivers), or specific hardware, here.

drivers/usb/gadget/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_USB_AT91)		+= at91_udc.o
 g_zero-objs			:= zero.o usbstring.o config.o epautoconf.o
 g_ether-objs			:= ether.o usbstring.o config.o epautoconf.o
 g_serial-objs			:= serial.o usbstring.o config.o epautoconf.o
+g_midi-objs			:= gmidi.o usbstring.o config.o epautoconf.o
 gadgetfs-objs			:= inode.o
 g_file_storage-objs		:= file_storage.o usbstring.o config.o \
 					epautoconf.o
@@ -28,4 +29,5 @@ obj-$(CONFIG_USB_ETH)		+= g_ether.o
 obj-$(CONFIG_USB_GADGETFS)	+= gadgetfs.o
 obj-$(CONFIG_USB_FILE_STORAGE)	+= g_file_storage.o
 obj-$(CONFIG_USB_G_SERIAL)	+= g_serial.o
+obj-$(CONFIG_USB_MIDI_GADGET)	+= g_midi.o
 

include/linux/usb/audio.h

+/*
+ * <linux/usb/audio.h> -- USB Audio definitions.
+ *
+ * Copyright (C) 2006 Thumtronics Pty Ltd.
+ * Developed for Thumtronics by Grey Innovation
+ * Ben Williamson <ben.williamson@greyinnovation.com>
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * License ("GPL") version 2, as published by the Free Software Foundation.
+ *
+ * This file holds USB constants and structures defined
+ * by the USB Device Class Definition for Audio Devices.
+ * Comments below reference relevant sections of that document:
+ *
+ * http://www.usb.org/developers/devclass_docs/audio10.pdf
+ */
+
+#ifndef __LINUX_USB_AUDIO_H
+#define __LINUX_USB_AUDIO_H
+
+#include <linux/types.h>
+
+/* A.2 Audio Interface Subclass Codes */
+#define USB_SUBCLASS_AUDIOCONTROL	0x01
+#define USB_SUBCLASS_AUDIOSTREAMING	0x02
+#define USB_SUBCLASS_MIDISTREAMING	0x03
+
+/* 4.3.2  Class-Specific AC Interface Descriptor */
+struct usb_ac_header_descriptor {
+	__u8  bLength;			// 8+n
+	__u8  bDescriptorType;		// USB_DT_CS_INTERFACE
+	__u8  bDescriptorSubtype;	// USB_MS_HEADER
+	__le16 bcdADC;			// 0x0100
+	__le16 wTotalLength;		// includes Unit and Terminal desc.
+	__u8  bInCollection;		// n
+	__u8  baInterfaceNr[];		// [n]
+} __attribute__ ((packed));
+
+#define USB_DT_AC_HEADER_SIZE(n)	(8+(n))
+
+/* As above, but more useful for defining your own descriptors: */
+#define DECLARE_USB_AC_HEADER_DESCRIPTOR(n) 			\
+struct usb_ac_header_descriptor_##n {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubtype;				\
+	__le16 bcdADC;						\
+	__le16 wTotalLength;					\
+	__u8  bInCollection;					\
+	__u8  baInterfaceNr[n];					\
+} __attribute__ ((packed))
+
+#endif

include/linux/usb/midi.h

+/*
+ * <linux/usb/midi.h> -- USB MIDI definitions.
+ *
+ * Copyright (C) 2006 Thumtronics Pty Ltd.
+ * Developed for Thumtronics by Grey Innovation
+ * Ben Williamson <ben.williamson@greyinnovation.com>
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * License ("GPL") version 2, as published by the Free Software Foundation.
+ *
+ * This file holds USB constants and structures defined
+ * by the USB Device Class Definition for MIDI Devices.
+ * Comments below reference relevant sections of that document:
+ *
+ * http://www.usb.org/developers/devclass_docs/midi10.pdf
+ */
+
+#ifndef __LINUX_USB_MIDI_H
+#define __LINUX_USB_MIDI_H
+
+#include <linux/types.h>
+
+/* A.1  MS Class-Specific Interface Descriptor Subtypes */
+#define USB_MS_HEADER		0x01
+#define USB_MS_MIDI_IN_JACK	0x02
+#define USB_MS_MIDI_OUT_JACK	0x03
+#define USB_MS_ELEMENT		0x04
+
+/* A.2  MS Class-Specific Endpoint Descriptor Subtypes */
+#define USB_MS_GENERAL		0x01
+
+/* A.3  MS MIDI IN and OUT Jack Types */
+#define USB_MS_EMBEDDED		0x01
+#define USB_MS_EXTERNAL		0x02
+
+/* 6.1.2.1  Class-Specific MS Interface Header Descriptor */
+struct usb_ms_header_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubtype;
+	__le16 bcdMSC;
+	__le16 wTotalLength;
+} __attribute__ ((packed));
+
+#define USB_DT_MS_HEADER_SIZE	7
+
+/* 6.1.2.2  MIDI IN Jack Descriptor */
+struct usb_midi_in_jack_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;		// USB_DT_CS_INTERFACE
+	__u8  bDescriptorSubtype;	// USB_MS_MIDI_IN_JACK
+	__u8  bJackType;		// USB_MS_EMBEDDED/EXTERNAL
+	__u8  bJackID;
+	__u8  iJack;
+} __attribute__ ((packed));
+
+#define USB_DT_MIDI_IN_SIZE	6
+
+struct usb_midi_source_pin {
+	__u8  baSourceID;
+	__u8  baSourcePin;
+} __attribute__ ((packed));
+
+/* 6.1.2.3  MIDI OUT Jack Descriptor */
+struct usb_midi_out_jack_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;		// USB_DT_CS_INTERFACE
+	__u8  bDescriptorSubtype;	// USB_MS_MIDI_OUT_JACK
+	__u8  bJackType;		// USB_MS_EMBEDDED/EXTERNAL
+	__u8  bJackID;
+	__u8  bNrInputPins;		// p
+	struct usb_midi_source_pin pins[]; // [p]
+	/*__u8  iJack;  -- ommitted due to variable-sized pins[] */
+} __attribute__ ((packed));
+
+#define USB_DT_MIDI_OUT_SIZE(p)	(7 + 2 * (p))
+
+/* As above, but more useful for defining your own descriptors: */
+#define DECLARE_USB_MIDI_OUT_JACK_DESCRIPTOR(p)			\
+struct usb_midi_out_jack_descriptor_##p {			\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubtype;				\
+	__u8  bJackType;					\
+	__u8  bJackID;						\
+	__u8  bNrInputPins;					\
+	struct usb_midi_source_pin pins[p];			\
+	__u8  iJack;						\
+} __attribute__ ((packed))
+
+/* 6.2.2  Class-Specific MS Bulk Data Endpoint Descriptor */
+struct usb_ms_endpoint_descriptor {
+	__u8  bLength;			// 4+n
+	__u8  bDescriptorType;		// USB_DT_CS_ENDPOINT
+	__u8  bDescriptorSubtype;	// USB_MS_GENERAL
+	__u8  bNumEmbMIDIJack;		// n
+	__u8  baAssocJackID[];		// [n]
+} __attribute__ ((packed));
+
+#define USB_DT_MS_ENDPOINT_SIZE(n)	(4 + (n))
+
+/* As above, but more useful for defining your own descriptors: */
+#define DECLARE_USB_MS_ENDPOINT_DESCRIPTOR(n)			\
+struct usb_ms_endpoint_descriptor_##n {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubtype;				\
+	__u8  bNumEmbMIDIJack;					\
+	__u8  baAssocJackID[n];					\
+} __attribute__ ((packed))
+
+#endif