[RFC] g_midi: New USB MIDI Gadget class driver.

[RFC] g_midi: New USB MIDI Gadget class driver.

[Ben Williamson]

[-- Attachment #1: Type: text/plain, Size: 1626 bytes --]

Hi all,

This patch adds a USB MIDI Gadget driver. This driver is glue between
the USB gadget interface and the ALSA MIDI interface. It allows an
embedded Linux system to appear as a class-compliant USB-MIDI device
to a host system on the other end of a USB cable.

Much of the code is borrowed from zero.c, usbmidi.c and usbaudio.c;
my thanks to David, Clemens and Takashi for their work.

Included are usb_audio.h and usb_midi.h containing definitions from
the relevant USB specifications for USB audio and USB MIDI devices.
The definitions of struct usb_ms_header_descriptor and struct
usb_ms_endpoint_descriptor are the same as those that appear in
sound/usb/usbmidi.c, with the intention of that file including
<linux/usb_midi.h> instead. I have not included that change here.

This patch is against v2.6.17. I have tested using dummy_hcd inside
user-mode linux, and using s3c2410_udc. Testing with user-mode linux
requires minor changes to a few Kconfig files in order to enable the
USB and sound subsystems with ARCH=um.

I have tested playing a midi file with aplaymidi at one end and dumping
the events with amidi at the other (in both directions) as well as
connecting to a Mac running a synth with Garage Band.

All comments are welcome. If the response is favourable then I'll submit
this driver to the USB folks for inclusion.

Cheers,

- Ben.


P.S. My apologies if it's inappropriate to cross-post to linux-usb-devel
and alsa-devel, I'm hoping you're both interested. :)

P.P.S. My first attempt at emailing a patch with Thunderbird. Whitespace
was munged when inline, so I hope a text/plain attachment is ok.


[-- Attachment #2: 0001-g_midi-New-USB-MIDI-Gadget-class-driver.txt --]
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---
 drivers/usb/gadget/Kconfig  |   13 
 drivers/usb/gadget/Makefile |    2 
 drivers/usb/gadget/gmidi.c  | 1292 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/usb_audio.h   |   52 ++
 include/linux/usb_midi.h    |  110 ++++
 5 files changed, 1469 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 363b2ad..6835649 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -404,6 +404,19 @@ 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 EXPERIMENTAL
+	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.
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index 5a28e61..e71e086 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -15,6 +15,7 @@ #
 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
 
diff --git a/drivers/usb/gadget/gmidi.c b/drivers/usb/gadget/gmidi.c
new file mode 100644
index 0000000..4fe6323
--- /dev/null
+++ b/drivers/usb/gadget/gmidi.c
@@ -0,0 +1,1292 @@
+/*
+ * gmidi.c -- USB MIDI Gadget Driver
+ *
+ * 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 code is based in part on:
+ *
+ * Gadget Zero driver, Copyright (C) 2003-2004 David Brownell.
+ * USB Audio driver, Copyright (C) 2002 by Takashi Iwai.
+ * USB MIDI driver, Copyright (C) 2002-2005 Clemens Ladisch.
+ *
+ * Refer to the USB Device Class Definition for MIDI Devices:
+ * http://www.usb.org/developers/devclass_docs/midi10.pdf
+ */
+
+#define DEBUG 1
+// #define VERBOSE
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/utsname.h>
+#include <linux/device.h>
+#include <linux/moduleparam.h>
+
+#include <sound/driver.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/rawmidi.h>
+#include <sound/asequencer.h>
+
+#include <linux/usb_ch9.h>
+#include <linux/usb_gadget.h>
+#include <linux/usb_audio.h>
+#include <linux/usb_midi.h>
+
+#include "gadget_chips.h"
+
+MODULE_AUTHOR("Ben Williamson");
+MODULE_LICENSE("GPL v2");
+
+#define DRIVER_VERSION "1.0"
+
+static const char shortname[] = "g_midi";
+static const char longname[] = "MIDI Gadget";
+
+/*
+ * this version autoconfigures as much as possible,
+ * which is reasonable for most "bulk-only" drivers.
+ */
+static const char *EP_IN_NAME;
+static const char *EP_OUT_NAME;
+
+
+/* big enough to hold our biggest descriptor */
+#define USB_BUFSIZ 256
+
+
+/* This is a gadget, and the IN/OUT naming is from the host's perspective.
+   USB -> OUT endpoint -> rawmidi
+   USB <- IN endpoint  <- rawmidi */
+struct gmidi_in_port {
+	struct gmidi_device* dev;
+	int active;
+	uint8_t cable;		/* cable number << 4 */
+	uint8_t state;
+#define STATE_UNKNOWN	0
+#define STATE_1PARAM	1
+#define STATE_2PARAM_1	2
+#define STATE_2PARAM_2	3
+#define STATE_SYSEX_0	4
+#define STATE_SYSEX_1	5
+#define STATE_SYSEX_2	6
+	uint8_t data[2];
+};
+
+struct gmidi_device {
+	spinlock_t		lock;
+	struct usb_gadget	*gadget;
+	struct usb_request	*req;		/* for control responses */
+
+	u8			config;
+	struct usb_ep		*in_ep, *out_ep;
+
+	struct snd_card 	*card;
+	struct snd_rawmidi	*rmidi;
+	struct snd_rawmidi_substream *in_substream;
+	struct snd_rawmidi_substream *out_substream;
+
+	/* For the moment we only support one port in
+	   each direction, but in_port is kept as a
+	   separate struct so we can have more later. */
+	struct gmidi_in_port	in_port;
+	unsigned long		out_triggered;
+	struct tasklet_struct	tasklet;
+};
+
+static void gmidi_transmit(struct gmidi_device* dev, struct usb_request* req);
+
+
+#define xprintk(d,level,fmt,args...) \
+	dev_printk(level , &(d)->gadget->dev , fmt , ## args)
+
+#ifdef DEBUG
+#define DBG(dev,fmt,args...) \
+	xprintk(dev , KERN_DEBUG , fmt , ## args)
+#else
+#define DBG(dev,fmt,args...) \
+	do { } while (0)
+#endif /* DEBUG */
+
+#ifdef VERBOSE
+#define VDBG	DBG
+#else
+#define VDBG(dev,fmt,args...) \
+	do { } while (0)
+#endif /* VERBOSE */
+
+#define ERROR(dev,fmt,args...) \
+	xprintk(dev , KERN_ERR , fmt , ## args)
+#define WARN(dev,fmt,args...) \
+	xprintk(dev , KERN_WARNING , fmt , ## args)
+#define INFO(dev,fmt,args...) \
+	xprintk(dev , KERN_INFO , fmt , ## args)
+
+
+static unsigned buflen = 256;
+static unsigned qlen = 32;
+
+module_param(buflen, uint, S_IRUGO);
+module_param(qlen, uint, S_IRUGO);
+
+
+/* Thanks to Grey Innovation for donating this product ID.
+ *
+ * DO NOT REUSE THESE IDs with a protocol-incompatible driver!!  Ever!!
+ * Instead:  allocate your own, using normal USB-IF procedures.
+ */
+#define DRIVER_VENDOR_NUM	0x17b3		/* Grey Innovation */
+#define DRIVER_PRODUCT_NUM	0x0004		/* Linux-USB "MIDI Gadget" */
+
+
+/*
+ * DESCRIPTORS ... most are static, but strings and (full)
+ * configuration descriptors are built on demand.
+ */
+
+#define STRING_MANUFACTURER	25
+#define STRING_PRODUCT		42
+#define STRING_SERIAL		101
+#define STRING_MIDI_GADGET	250
+
+/* We only have the one configuration, it's number 1. */
+#define	GMIDI_CONFIG		1
+
+/* We have two interfaces- AudioControl and MIDIStreaming */
+#define GMIDI_AC_INTERFACE	0
+#define GMIDI_MS_INTERFACE	1
+#define GMIDI_NUM_INTERFACES	2
+
+/* B.1  Device Descriptor */
+static struct usb_device_descriptor device_desc = {
+	.bLength =		USB_DT_DEVICE_SIZE,
+	.bDescriptorType =	USB_DT_DEVICE,
+	.bcdUSB =		__constant_cpu_to_le16(0x0200),
+	.bDeviceClass =		USB_CLASS_PER_INTERFACE,
+	.idVendor =		__constant_cpu_to_le16(DRIVER_VENDOR_NUM),
+	.idProduct =		__constant_cpu_to_le16(DRIVER_PRODUCT_NUM),
+	.iManufacturer =	STRING_MANUFACTURER,
+	.iProduct =		STRING_PRODUCT,
+	.iSerialNumber =	STRING_SERIAL,
+	.bNumConfigurations =	1,
+};
+
+/* B.2  Configuration Descriptor */
+static struct usb_config_descriptor config_desc = {
+	.bLength =		USB_DT_CONFIG_SIZE,
+	.bDescriptorType =	USB_DT_CONFIG,
+	/* compute wTotalLength on the fly */
+	.bNumInterfaces =	GMIDI_NUM_INTERFACES,
+	.bConfigurationValue =	GMIDI_CONFIG,
+	.iConfiguration =	STRING_MIDI_GADGET,
+	/*
+	 * FIXME: When embedding this driver in a device,
+	 * these need to be set to reflect the actual
+	 * power properties of the device. Is it selfpowered?
+	 */
+	.bmAttributes =		USB_CONFIG_ATT_ONE,
+	.bMaxPower =		1,
+};
+
+/* B.3.1  Standard AC Interface Descriptor */
+static const struct usb_interface_descriptor ac_interface_desc = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	.bInterfaceNumber =	GMIDI_AC_INTERFACE,
+	.bNumEndpoints =	0,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOCONTROL,
+	.iInterface =		STRING_MIDI_GADGET,
+};
+
+/* B.3.2  Class-Specific AC Interface Descriptor */
+static const struct USB_AC_HEADER_DESCRIPTOR(1) ac_header_desc = {
+	.bLength =		USB_DT_AC_HEADER_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_HEADER,
+	.bcdADC =		__constant_cpu_to_le16(0x0100),
+	.wTotalLength =		USB_DT_AC_HEADER_SIZE(1),
+	.bInCollection =	1,
+	.baInterfaceNr = {
+		[0] =		GMIDI_MS_INTERFACE,
+	}
+};
+
+/* B.4.1  Standard MS Interface Descriptor */
+static const struct usb_interface_descriptor ms_interface_desc = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	.bInterfaceNumber =	GMIDI_MS_INTERFACE,
+	.bNumEndpoints =	2,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_MIDISTREAMING,
+	.iInterface =		STRING_MIDI_GADGET,
+};
+
+/* B.4.2  Class-Specific MS Interface Descriptor */
+static const struct usb_ms_header_descriptor ms_header_desc = {
+	.bLength =		USB_DT_MS_HEADER_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_HEADER,
+	.bcdMSC =		__constant_cpu_to_le16(0x0100),
+	.wTotalLength =		USB_DT_MS_HEADER_SIZE + 2*USB_DT_MIDI_IN_SIZE + 2*USB_DT_MIDI_OUT_SIZE(1),
+};
+
+#define JACK_IN_EMB	1
+#define JACK_IN_EXT	2
+#define JACK_OUT_EMB	3
+#define JACK_OUT_EXT	4
+
+/* B.4.3  MIDI IN Jack Descriptors */
+static const struct usb_midi_in_jack_descriptor jack_in_emb_desc = {
+	.bLength =		USB_DT_MIDI_IN_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_MIDI_IN_JACK,
+	.bJackType =		USB_MS_EMBEDDED,
+	.bJackID =		JACK_IN_EMB,
+};
+
+static const struct usb_midi_in_jack_descriptor jack_in_ext_desc = {
+	.bLength =		USB_DT_MIDI_IN_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_MIDI_IN_JACK,
+	.bJackType =		USB_MS_EXTERNAL,
+	.bJackID =		JACK_IN_EXT,
+};
+
+/* B.4.4  MIDI OUT Jack Descriptors */
+static const struct USB_MIDI_OUT_JACK_DESCRIPTOR(1) jack_out_emb_desc = {
+	.bLength =		USB_DT_MIDI_OUT_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_MIDI_OUT_JACK,
+	.bJackType =		USB_MS_EMBEDDED,
+	.bJackID =		JACK_OUT_EMB,
+	.bNrInputPins =		1,
+	.pins = {
+		[0] = {
+			.baSourceID =	JACK_IN_EXT,
+			.baSourcePin =	1,
+		}
+	}
+};
+
+static const struct USB_MIDI_OUT_JACK_DESCRIPTOR(1) jack_out_ext_desc = {
+	.bLength =		USB_DT_MIDI_OUT_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_MIDI_OUT_JACK,
+	.bJackType =		USB_MS_EXTERNAL,
+	.bJackID =		JACK_OUT_EXT,
+	.bNrInputPins =		1,
+	.pins = {
+		[0] = {
+			.baSourceID =	JACK_IN_EMB,
+			.baSourcePin =	1,
+		}
+	}
+};
+
+/* B.5.1  Standard Bulk OUT Endpoint Descriptor */
+static struct usb_endpoint_descriptor bulk_out_desc = {
+	.bLength =		USB_DT_ENDPOINT_AUDIO_SIZE,
+	.bDescriptorType =	USB_DT_ENDPOINT,
+	.bEndpointAddress =	USB_DIR_OUT,
+	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
+};
+
+/* B.5.2  Class-specific MS Bulk OUT Endpoint Descriptor */
+static const struct USB_MS_ENDPOINT_DESCRIPTOR(1) ms_out_desc = {
+	.bLength =		USB_DT_MS_ENDPOINT_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_ENDPOINT,
+	.bDescriptorSubtype =	USB_MS_GENERAL,
+	.bNumEmbMIDIJack =	1,
+	.baAssocJackID = {
+		[0] =		JACK_IN_EMB,
+	}
+};
+
+/* B.6.1  Standard Bulk IN Endpoint Descriptor */
+static struct usb_endpoint_descriptor bulk_in_desc = {
+	.bLength =		USB_DT_ENDPOINT_AUDIO_SIZE,
+	.bDescriptorType =	USB_DT_ENDPOINT,
+	.bEndpointAddress =	USB_DIR_IN,
+	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
+};
+
+/* B.6.2  Class-specific MS Bulk IN Endpoint Descriptor */
+static const struct USB_MS_ENDPOINT_DESCRIPTOR(1) ms_in_desc = {
+	.bLength =		USB_DT_MS_ENDPOINT_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_ENDPOINT,
+	.bDescriptorSubtype =	USB_MS_GENERAL,
+	.bNumEmbMIDIJack =	1,
+	.baAssocJackID = {
+		[0] =		JACK_OUT_EMB,
+	}
+};
+
+static const struct usb_descriptor_header *gmidi_function [] = {
+	(struct usb_descriptor_header *)&ac_interface_desc,
+	(struct usb_descriptor_header *)&ac_header_desc,
+	(struct usb_descriptor_header *)&ms_interface_desc,
+
+	(struct usb_descriptor_header *)&ms_header_desc,
+	(struct usb_descriptor_header *)&jack_in_emb_desc,
+	(struct usb_descriptor_header *)&jack_in_ext_desc,
+	(struct usb_descriptor_header *)&jack_out_emb_desc,
+	(struct usb_descriptor_header *)&jack_out_ext_desc,
+	/* If you add more jacks, update ms_header_desc.wTotalLength */
+
+	(struct usb_descriptor_header *)&bulk_out_desc,
+	(struct usb_descriptor_header *)&ms_out_desc,
+	(struct usb_descriptor_header *)&bulk_in_desc,
+	(struct usb_descriptor_header *)&ms_in_desc,
+	NULL,
+};
+
+static char manufacturer[50];
+static char serial[40];
+
+/* static strings, in UTF-8 */
+static struct usb_string strings [] = {
+	{ STRING_MANUFACTURER, manufacturer, },
+	{ STRING_PRODUCT, longname, },
+	{ STRING_SERIAL, serial, },
+	{ STRING_MIDI_GADGET, longname, },
+	{  }			/* end of list */
+};
+
+static struct usb_gadget_strings stringtab = {
+	.language	= 0x0409,	/* en-us */
+	.strings	= strings,
+};
+
+static int config_buf(struct usb_gadget *gadget,
+		u8 *buf, u8 type, unsigned index)
+{
+	int len;
+
+	/* two configurations will always be index 0 and index 1 */
+	if (index > 1) {
+		return -EINVAL;
+	}
+
+	len = usb_gadget_config_buf(&config_desc,
+			buf, USB_BUFSIZ, gmidi_function);
+	if (len < 0) {
+		return len;
+	}
+	((struct usb_config_descriptor *)buf)->bDescriptorType = type;
+	return len;
+}
+
+static struct usb_request* alloc_ep_req(struct usb_ep *ep, unsigned length)
+{
+	struct usb_request	*req;
+
+	req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+	if (req) {
+		req->length = length;
+		req->buf = usb_ep_alloc_buffer(ep, length,
+				&req->dma, GFP_ATOMIC);
+		if (!req->buf) {
+			usb_ep_free_request(ep, req);
+			req = NULL;
+		}
+	}
+	return req;
+}
+
+static void free_ep_req(struct usb_ep *ep, struct usb_request *req)
+{
+	if (req->buf) {
+		usb_ep_free_buffer(ep, req->buf, req->dma, req->length);
+	}
+	usb_ep_free_request(ep, req);
+}
+
+static const uint8_t gmidi_cin_length[] = {
+	0, 0, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 2, 2, 3, 1
+};
+
+/*
+ * Receives a chunk of MIDI data.
+ */
+static void gmidi_read_data(struct usb_ep *ep, int cable,
+				   uint8_t* data, int length)
+{
+	struct gmidi_device *dev = ep->driver_data;
+	/* cable is ignored, because for now we only have one. */
+
+	if (!dev->out_substream) {
+		/* Nobody is listening - throw it on the floor. */
+		return;
+	}
+	if (!test_bit(dev->out_substream->number, &dev->out_triggered)) {
+		return;
+	}
+	snd_rawmidi_receive(dev->out_substream, data, length);
+}
+
+static void gmidi_handle_out_data(struct usb_ep *ep, struct usb_request *req)
+{
+	unsigned i;
+	u8 *buf = req->buf;
+
+	for (i = 0; i + 3 < req->actual; i += 4) {
+		if (buf[i] != 0) {
+			int cable = buf[i] >> 4;
+			int length = gmidi_cin_length[buf[i] & 0x0f];
+			gmidi_read_data(ep, cable, &buf[i + 1], length);
+		}
+	}
+}
+
+static void gmidi_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct gmidi_device *dev = ep->driver_data;
+	int status = req->status;
+
+	VDBG(dev, "in gmidi_complete %d bytes, status=%d\n", req->actual, status);
+	switch (status) {
+
+	case 0: 			/* normal completion */
+		if (ep == dev->out_ep) {
+			/* we received stuff.
+			   req is queued again, below */
+			gmidi_handle_out_data(ep, req);
+		} else {
+			/* our transmit completed.
+			   see if there's more to go.
+			   gmidi_transmit eats req, don't queue it again. */
+			gmidi_transmit(dev, req);
+			return;
+		}
+		break;
+
+	/* this endpoint is normally active while we're configured */
+	case -ECONNABORTED: 		/* hardware forced ep reset */
+	case -ECONNRESET:		/* request dequeued */
+	case -ESHUTDOWN:		/* disconnect from host */
+		VDBG(dev, "%s gone (%d), %d/%d\n", ep->name, status,
+				req->actual, req->length);
+		if (ep == dev->out_ep) {
+			gmidi_handle_out_data(ep, req);
+		}
+		free_ep_req(ep, req);
+		return;
+
+	case -EOVERFLOW:		/* buffer overrun on read means that
+					 * we didn't provide a big enough
+					 * buffer.
+					 */
+	default:
+		DBG(dev, "%s complete --> %d, %d/%d\n", ep->name,
+				status, req->actual, req->length);
+		break;
+	case -EREMOTEIO:		/* short read */
+		break;
+	}
+
+	status = usb_ep_queue(ep, req, GFP_ATOMIC);
+	if (status) {
+		ERROR(dev, "kill %s:  resubmit %d bytes --> %d\n",
+				ep->name, req->length, status);
+		usb_ep_set_halt(ep);
+		/* FIXME recover later ... somehow */
+	}
+}
+
+static int set_gmidi_config(struct gmidi_device *dev, gfp_t gfp_flags)
+{
+	int result = 0;
+	struct usb_ep *ep;
+	struct usb_gadget *gadget = dev->gadget;
+
+	gadget_for_each_ep(ep, gadget) {
+		const struct usb_endpoint_descriptor *d;
+
+		/* one endpoint writes data back IN to the host */
+		if (strcmp(ep->name, EP_IN_NAME) == 0) {
+			d = &bulk_in_desc;
+			result = usb_ep_enable(ep, d);
+			if (result == 0) {
+				ep->driver_data = dev;
+				dev->in_ep = ep;
+				continue;
+			}
+
+		/* one endpoint reads (sinks) anything out (from the host) */
+		} else if (strcmp(ep->name, EP_OUT_NAME) == 0) {
+			d = &bulk_out_desc;
+			result = usb_ep_enable(ep, d);
+			if (result == 0) {
+				ep->driver_data = dev;
+				dev->out_ep = ep;
+				continue;
+			}
+
+		/* ignore any other endpoints */
+		} else {
+			continue;
+		}
+
+		/* stop on error */
+		ERROR(dev, "can't start %s, result %d\n", ep->name, result);
+		break;
+	}
+
+	/* allocate a bunch of read buffers and queue them all at once.
+	 * we buffer at most 'qlen' transfers; fewer if any need more
+	 * than 'buflen' bytes each.
+	 */
+	if (result == 0) {
+		struct usb_request *req;
+		unsigned i;
+
+		ep = dev->out_ep;
+		for (i = 0; i < qlen && result == 0; i++) {
+			req = alloc_ep_req(ep, buflen);
+			if (req) {
+				req->complete = gmidi_complete;
+				result = usb_ep_queue(ep, req, GFP_ATOMIC);
+				if (result) {
+					DBG(dev, "%s queue req --> %d\n",
+							ep->name, result);
+				}
+			} else {
+				result = -ENOMEM;
+			}
+		}
+	}
+	if (result == 0) {
+		DBG (dev, "qlen %d, buflen %d\n", qlen, buflen);
+	}
+
+	/* caller is responsible for cleanup on error */
+	return result;
+}
+
+
+static void gmidi_reset_config(struct gmidi_device *dev)
+{
+	if (dev->config == 0) {
+		return;
+	}
+
+	DBG(dev, "reset config\n");
+
+	/* just disable endpoints, forcing completion of pending i/o.
+	 * all our completion handlers free their requests in this case.
+	 */
+	if (dev->in_ep) {
+		usb_ep_disable(dev->in_ep);
+		dev->in_ep = NULL;
+	}
+	if (dev->out_ep) {
+		usb_ep_disable(dev->out_ep);
+		dev->out_ep = NULL;
+	}
+	dev->config = 0;
+}
+
+/* change our operational config.  this code must agree with the code
+ * that returns config descriptors, and altsetting code.
+ *
+ * it's also responsible for power management interactions. some
+ * configurations might not work with our current power sources.
+ *
+ * note that some device controller hardware will constrain what this
+ * code can do, perhaps by disallowing more than one configuration or
+ * by limiting configuration choices (like the pxa2xx).
+ */
+static int
+gmidi_set_config(struct gmidi_device *dev, unsigned number, gfp_t gfp_flags)
+{
+	int result = 0;
+	struct usb_gadget *gadget = dev->gadget;
+
+	if (number == dev->config) {
+		return 0;
+	}
+
+	if (gadget_is_sa1100(gadget) && dev->config) {
+		/* tx fifo is full, but we can't clear it...*/
+		INFO(dev, "can't change configurations\n");
+		return -ESPIPE;
+	}
+	gmidi_reset_config(dev);
+
+	switch (number) {
+	case GMIDI_CONFIG:
+		result = set_gmidi_config(dev, gfp_flags);
+		break;
+	default:
+		result = -EINVAL;
+		/* FALL THROUGH */
+	case 0:
+		return result;
+	}
+
+	if (!result && (!dev->in_ep || !dev->out_ep)) {
+		result = -ENODEV;
+	}
+	if (result) {
+		gmidi_reset_config(dev);
+	} else {
+		char *speed;
+
+		switch (gadget->speed) {
+		case USB_SPEED_LOW:	speed = "low"; break;
+		case USB_SPEED_FULL:	speed = "full"; break;
+		case USB_SPEED_HIGH:	speed = "high"; break;
+		default: 		speed = "?"; break;
+		}
+
+		dev->config = number;
+		INFO(dev, "%s speed\n", speed);
+	}
+	return result;
+}
+
+
+static void gmidi_setup_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	if (req->status || req->actual != req->length) {
+		DBG((struct gmidi_device *) ep->driver_data,
+				"setup complete --> %d, %d/%d\n",
+				req->status, req->actual, req->length);
+	}
+}
+
+/*
+ * The setup() callback implements all the ep0 functionality that's
+ * not handled lower down, in hardware or the hardware driver (like
+ * device and endpoint feature flags, and their status).  It's all
+ * housekeeping for the gadget function we're implementing.  Most of
+ * the work is in config-specific setup.
+ */
+static int gmidi_setup(struct usb_gadget *gadget,
+			const struct usb_ctrlrequest *ctrl)
+{
+	struct gmidi_device *dev = get_gadget_data(gadget);
+	struct usb_request *req = dev->req;
+	int value = -EOPNOTSUPP;
+	u16 w_index = le16_to_cpu(ctrl->wIndex);
+	u16 w_value = le16_to_cpu(ctrl->wValue);
+	u16 w_length = le16_to_cpu(ctrl->wLength);
+
+	/* usually this stores reply data in the pre-allocated ep0 buffer,
+	 * but config change events will reconfigure hardware.
+	 */
+	req->zero = 0;
+	switch (ctrl->bRequest) {
+
+	case USB_REQ_GET_DESCRIPTOR:
+		if (ctrl->bRequestType != USB_DIR_IN) {
+			goto unknown;
+		}
+		switch (w_value >> 8) {
+
+		case USB_DT_DEVICE:
+			value = min(w_length, (u16) sizeof(device_desc));
+			memcpy(req->buf, &device_desc, value);
+			break;
+		case USB_DT_CONFIG:
+			value = config_buf(gadget, req->buf,
+					w_value >> 8,
+					w_value & 0xff);
+			if (value >= 0) {
+				value = min(w_length, (u16)value);
+			}
+			break;
+
+		case USB_DT_STRING:
+			/* wIndex == language code.
+			 * this driver only handles one language, you can
+			 * add string tables for other languages, using
+			 * any UTF-8 characters
+			 */
+			value = usb_gadget_get_string(&stringtab,
+					w_value & 0xff, req->buf);
+			if (value >= 0) {
+				value = min(w_length, (u16)value);
+			}
+			break;
+		}
+		break;
+
+	/* currently two configs, two speeds */
+	case USB_REQ_SET_CONFIGURATION:
+		if (ctrl->bRequestType != 0) {
+			goto unknown;
+		}
+		if (gadget->a_hnp_support) {
+			DBG(dev, "HNP available\n");
+		} else if (gadget->a_alt_hnp_support) {
+			DBG(dev, "HNP needs a different root port\n");
+		} else {
+			VDBG(dev, "HNP inactive\n");
+		}
+		spin_lock(&dev->lock);
+		value = gmidi_set_config(dev, w_value, GFP_ATOMIC);
+		spin_unlock(&dev->lock);
+		break;
+	case USB_REQ_GET_CONFIGURATION:
+		if (ctrl->bRequestType != USB_DIR_IN) {
+			goto unknown;
+		}
+		*(u8 *)req->buf = dev->config;
+		value = min(w_length, (u16)1);
+		break;
+
+	/* until we add altsetting support, or other interfaces,
+	 * only 0/0 are possible.  pxa2xx only supports 0/0 (poorly)
+	 * and already killed pending endpoint I/O.
+	 */
+	case USB_REQ_SET_INTERFACE:
+		if (ctrl->bRequestType != USB_RECIP_INTERFACE) {
+			goto unknown;
+		}
+		spin_lock(&dev->lock);
+		if (dev->config && w_index < GMIDI_NUM_INTERFACES && w_value == 0) {
+			u8		config = dev->config;
+
+			/* resets interface configuration, forgets about
+			 * previous transaction state (queued bufs, etc)
+			 * and re-inits endpoint state (toggle etc)
+			 * no response queued, just zero status == success.
+			 * if we had more than one interface we couldn't
+			 * use this "reset the config" shortcut.
+			 */
+			gmidi_reset_config(dev);
+			gmidi_set_config(dev, config, GFP_ATOMIC);
+			value = 0;
+		}
+		spin_unlock(&dev->lock);
+		break;
+	case USB_REQ_GET_INTERFACE:
+		if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE)) {
+			goto unknown;
+		}
+		if (!dev->config) {
+			break;
+		}
+		if (w_index >= GMIDI_NUM_INTERFACES) {
+			value = -EDOM;
+			break;
+		}
+		*(u8 *)req->buf = 0;
+		value = min(w_length, (u16)1);
+		break;
+
+	default:
+unknown:
+		VDBG(dev, "unknown control req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+	}
+
+	/* respond with data transfer before status phase? */
+	if (value >= 0) {
+		req->length = value;
+		req->zero = value < w_length;
+		value = usb_ep_queue(gadget->ep0, req, GFP_ATOMIC);
+		if (value < 0) {
+			DBG(dev, "ep_queue --> %d\n", value);
+			req->status = 0;
+			gmidi_setup_complete(gadget->ep0, req);
+		}
+	}
+
+	/* device either stalls (value < 0) or reports success */
+	return value;
+}
+
+static void gmidi_disconnect(struct usb_gadget *gadget)
+{
+	struct gmidi_device *dev = get_gadget_data(gadget);
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	gmidi_reset_config(dev);
+
+	/* a more significant application might have some non-usb
+	 * activities to quiesce here, saving resources like power
+	 * or pushing the notification up a network stack.
+	 */
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	/* next we may get setup() calls to enumerate new connections;
+	 * or an unbind() during shutdown (including removing module).
+	 */
+}
+
+static void __exit gmidi_unbind(struct usb_gadget *gadget)
+{
+	struct gmidi_device *dev = get_gadget_data(gadget);
+	struct snd_card* card;
+
+	DBG(dev, "unbind\n");
+
+	card = dev->card;
+	dev->card = NULL;
+	if (card) {
+		snd_card_free(card);
+	}
+
+	/* we've already been disconnected ... no i/o is active */
+	if (dev->req) {
+		dev->req->length = USB_BUFSIZ;
+		free_ep_req(gadget->ep0, dev->req);
+	}
+	kfree(dev);
+	set_gadget_data(gadget, NULL);
+}
+
+static int gmidi_snd_free(struct snd_device *device)
+{
+	return 0;
+}
+
+static void gmidi_transmit_packet(struct usb_request* req, uint8_t p0,
+					uint8_t p1, uint8_t p2, uint8_t p3)
+{
+	unsigned length = req->length;
+
+	uint8_t* buf = (uint8_t*)req->buf + length;
+	buf[0] = p0;
+	buf[1] = p1;
+	buf[2] = p2;
+	buf[3] = p3;
+	req->length = length + 4;
+}
+
+/*
+ * Converts MIDI commands to USB MIDI packets.
+ */
+static void gmidi_transmit_byte(struct usb_request* req,
+				struct gmidi_in_port* port, uint8_t b)
+{
+	uint8_t p0 = port->cable;
+
+	if (b >= 0xf8) {
+		gmidi_transmit_packet(req, p0 | 0x0f, b, 0, 0);
+	} else if (b >= 0xf0) {
+		switch (b) {
+		case 0xf0:
+			port->data[0] = b;
+			port->state = STATE_SYSEX_1;
+			break;
+		case 0xf1:
+		case 0xf3:
+			port->data[0] = b;
+			port->state = STATE_1PARAM;
+			break;
+		case 0xf2:
+			port->data[0] = b;
+			port->state = STATE_2PARAM_1;
+			break;
+		case 0xf4:
+		case 0xf5:
+			port->state = STATE_UNKNOWN;
+			break;
+		case 0xf6:
+			gmidi_transmit_packet(req, p0 | 0x05, 0xf6, 0, 0);
+			port->state = STATE_UNKNOWN;
+			break;
+		case 0xf7:
+			switch (port->state) {
+			case STATE_SYSEX_0:
+				gmidi_transmit_packet(req, p0 | 0x05, 0xf7, 0, 0);
+				break;
+			case STATE_SYSEX_1:
+				gmidi_transmit_packet(req, p0 | 0x06, port->data[0], 0xf7, 0);
+				break;
+			case STATE_SYSEX_2:
+				gmidi_transmit_packet(req, p0 | 0x07, port->data[0], port->data[1], 0xf7);
+				break;
+			}
+			port->state = STATE_UNKNOWN;
+			break;
+		}
+	} else if (b >= 0x80) {
+		port->data[0] = b;
+		if (b >= 0xc0 && b <= 0xdf)
+			port->state = STATE_1PARAM;
+		else
+			port->state = STATE_2PARAM_1;
+	} else { /* b < 0x80 */
+		switch (port->state) {
+		case STATE_1PARAM:
+			if (port->data[0] < 0xf0) {
+				p0 |= port->data[0] >> 4;
+			} else {
+				p0 |= 0x02;
+				port->state = STATE_UNKNOWN;
+			}
+			gmidi_transmit_packet(req, p0, port->data[0], b, 0);
+			break;
+		case STATE_2PARAM_1:
+			port->data[1] = b;
+			port->state = STATE_2PARAM_2;
+			break;
+		case STATE_2PARAM_2:
+			if (port->data[0] < 0xf0) {
+				p0 |= port->data[0] >> 4;
+				port->state = STATE_2PARAM_1;
+			} else {
+				p0 |= 0x03;
+				port->state = STATE_UNKNOWN;
+			}
+			gmidi_transmit_packet(req, p0, port->data[0], port->data[1], b);
+			break;
+		case STATE_SYSEX_0:
+			port->data[0] = b;
+			port->state = STATE_SYSEX_1;
+			break;
+		case STATE_SYSEX_1:
+			port->data[1] = b;
+			port->state = STATE_SYSEX_2;
+			break;
+		case STATE_SYSEX_2:
+			gmidi_transmit_packet(req, p0 | 0x04, port->data[0], port->data[1], b);
+			port->state = STATE_SYSEX_0;
+			break;
+		}
+	}
+}
+
+static void gmidi_transmit(struct gmidi_device* dev, struct usb_request* req)
+{
+	struct usb_ep* ep = dev->in_ep;
+	struct gmidi_in_port* port = &dev->in_port;
+
+	if (!req) {
+		req = alloc_ep_req(ep, buflen);
+	}
+	if (!req) {
+		ERROR(dev, "gmidi_transmit: alloc_ep_request failed\n");
+		return;
+	}
+	req->length = 0;
+	req->complete = gmidi_complete;
+
+	if (port->active) {
+		while (req->length + 3 < buflen) {
+			uint8_t b;
+			if (snd_rawmidi_transmit(dev->in_substream, &b, 1) != 1) {
+				port->active = 0;
+				break;
+			}
+			gmidi_transmit_byte(req, port, b);
+		}
+	}
+	if (req->length > 0) {
+		usb_ep_queue(ep, req, GFP_ATOMIC);
+	} else {
+		free_ep_req(ep, req);
+	}
+}
+
+static void gmidi_in_tasklet(unsigned long data)
+{
+	struct gmidi_device* dev = (struct gmidi_device*)data;
+
+	gmidi_transmit(dev, NULL);
+}
+
+static int gmidi_in_open(struct snd_rawmidi_substream *substream)
+{
+	struct gmidi_device* dev = substream->rmidi->private_data;
+
+	VDBG(dev, "gmidi_in_open\n");
+	dev->in_substream = substream;
+	dev->in_port.state = STATE_UNKNOWN;
+	return 0;
+}
+
+static int gmidi_in_close(struct snd_rawmidi_substream *substream)
+{
+	VDBG(dev, "gmidi_in_close\n");
+	return 0;
+}
+
+static void gmidi_in_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct gmidi_device* dev = substream->rmidi->private_data;
+
+	VDBG(dev, "gmidi_in_trigger %d\n", up);
+	dev->in_port.active = up;
+	if (up) {
+		tasklet_hi_schedule(&dev->tasklet);
+	}
+}
+
+static int gmidi_out_open(struct snd_rawmidi_substream *substream)
+{
+	struct gmidi_device* dev = substream->rmidi->private_data;
+
+	VDBG(dev, "gmidi_out_open\n");
+	dev->out_substream = substream;
+	return 0;
+}
+
+static int gmidi_out_close(struct snd_rawmidi_substream *substream)
+{
+	VDBG(dev, "gmidi_out_close\n");
+	return 0;
+}
+
+static void gmidi_out_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct gmidi_device* dev = substream->rmidi->private_data;
+
+	VDBG(dev, "gmidi_out_trigger %d\n", up);
+	if (up) {
+		set_bit(substream->number, &dev->out_triggered);
+	} else {
+		clear_bit(substream->number, &dev->out_triggered);
+	}
+}
+
+static struct snd_rawmidi_ops gmidi_in_ops = {
+	.open = gmidi_in_open,
+	.close = gmidi_in_close,
+	.trigger = gmidi_in_trigger,
+};
+
+static struct snd_rawmidi_ops gmidi_out_ops = {
+	.open = gmidi_out_open,
+	.close = gmidi_out_close,
+	.trigger = gmidi_out_trigger
+};
+
+/* register as a sound "card" */
+static int gmidi_register_card(struct gmidi_device *dev)
+{
+	struct snd_card *card;
+	struct snd_rawmidi *rmidi;
+	int err;
+	int out_ports = 1;
+	int in_ports = 1;
+	static struct snd_device_ops ops = {
+		.dev_free = gmidi_snd_free,
+	};
+
+	card = snd_card_new(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1, THIS_MODULE, 0);
+	if (!card) {
+		ERROR(dev, "snd_card_new failed\n");
+		goto enomem;
+	}
+	dev->card = card;
+
+	err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, dev, &ops);
+	if (err < 0) {
+		ERROR(dev, "snd_device_new failed: error %d\n", err);
+		goto enomem;
+	}
+
+	strcpy(card->driver, longname);
+	strcpy(card->longname, longname);
+	strcpy(card->shortname, shortname);
+
+	/* Set up rawmidi */
+	dev->in_port.dev = dev;
+	dev->in_port.active = 0;
+	snd_component_add(card, "MIDI");
+	err = snd_rawmidi_new(card, "USB MIDI Gadget", 0,
+			      out_ports, in_ports, &rmidi);
+	if (err < 0) {
+		ERROR(dev, "snd_rawmidi_new failed: error %d\n", err);
+		goto enomem;
+	}
+	dev->rmidi = rmidi;
+	strcpy(rmidi->name, card->shortname);
+	rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
+			    SNDRV_RAWMIDI_INFO_INPUT |
+			    SNDRV_RAWMIDI_INFO_DUPLEX;
+	rmidi->private_data = dev;
+
+	/* Yes, rawmidi OUTPUT = USB IN, and rawmidi INPUT = USB OUT.
+	   It's an upside-down world being a gadget. */
+	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &gmidi_in_ops);
+	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &gmidi_out_ops);
+
+	snd_card_set_dev(card, &dev->gadget->dev);
+
+	/* register it - we're ready to go */
+	if (snd_card_register(card) < 0) {
+		ERROR(dev, "snd_card_register failed\n");
+		goto enomem;
+	}
+
+	VDBG(dev, "gmidi_register_card finished ok\n");
+	return 0;
+
+enomem:
+	if (dev->card) {
+		snd_card_free(dev->card);
+		dev->card = NULL;
+	}
+	return -ENOMEM;
+}
+
+/*
+ * Creates an output endpoint, and initializes output ports.
+ */
+static int __init gmidi_bind(struct usb_gadget *gadget)
+{
+	struct gmidi_device *dev;
+	struct usb_ep *ep;
+	int gcnum;
+
+	/* Bulk-only drivers like this one SHOULD be able to
+	 * autoconfigure on any sane usb controller driver,
+	 * but there may also be important quirks to address.
+	 */
+	usb_ep_autoconfig_reset(gadget);
+	ep = usb_ep_autoconfig(gadget, &bulk_in_desc);
+	if (!ep) {
+autoconf_fail:
+		printk(KERN_ERR "%s: can't autoconfigure on %s\n",
+			shortname, gadget->name);
+		return -ENODEV;
+	}
+	EP_IN_NAME = ep->name;
+	ep->driver_data = ep;	/* claim */
+	
+	ep = usb_ep_autoconfig(gadget, &bulk_out_desc);
+	if (!ep) {
+		goto autoconf_fail;
+	}
+	EP_OUT_NAME = ep->name;
+	ep->driver_data = ep;	/* claim */
+
+	gcnum = usb_gadget_controller_number(gadget);
+	if (gcnum >= 0) {
+		device_desc.bcdDevice = cpu_to_le16(0x0200 + gcnum);
+	} else {
+		/* gadget zero is so simple (for now, no altsettings) that
+		 * it SHOULD NOT have problems with bulk-capable hardware.
+		 * so warn about unrcognized controllers, don't panic.
+		 *
+		 * things like configuration and altsetting numbering
+		 * can need hardware-specific attention though.
+		 */
+		printk(KERN_WARNING "%s: controller '%s' not recognized\n",
+			shortname, gadget->name);
+		device_desc.bcdDevice = __constant_cpu_to_le16(0x9999);
+	}
+
+
+	/* ok, we made sense of the hardware ... */
+	dev = kzalloc(sizeof(*dev), SLAB_KERNEL);
+	if (!dev) {
+		return -ENOMEM;
+	}
+	spin_lock_init(&dev->lock);
+	dev->gadget = gadget;
+	set_gadget_data(gadget, dev);
+	tasklet_init(&dev->tasklet, gmidi_in_tasklet, (unsigned long)dev);
+
+	/* preallocate control response and buffer */
+	dev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
+	if (!dev->req) {
+		goto enomem;
+	}
+	dev->req->buf = usb_ep_alloc_buffer(gadget->ep0, USB_BUFSIZ,
+				&dev->req->dma, GFP_KERNEL);
+	if (!dev->req->buf) {
+		goto enomem;
+	}
+
+	dev->req->complete = gmidi_setup_complete;
+
+	device_desc.bMaxPacketSize0 = gadget->ep0->maxpacket;
+
+	gadget->ep0->driver_data = dev;
+
+	INFO(dev, "%s, version: " DRIVER_VERSION "\n", longname);
+	INFO(dev, "using %s, OUT %s IN %s\n", gadget->name,
+		EP_OUT_NAME, EP_IN_NAME);
+
+	snprintf(manufacturer, sizeof manufacturer, "%s %s with %s",
+		system_utsname.sysname, system_utsname.release,
+		gadget->name);
+
+	/* register as an ALSA sound card */
+	if (0 > gmidi_register_card(dev)) {
+		goto enomem;
+	}
+
+	VDBG(dev, "gmidi_bind finished ok\n");
+	return 0;
+
+enomem:
+	gmidi_unbind(gadget);
+	return -ENOMEM;
+}
+
+
+static void gmidi_suspend(struct usb_gadget *gadget)
+{
+	struct gmidi_device *dev = get_gadget_data(gadget);
+
+	if (gadget->speed == USB_SPEED_UNKNOWN) {
+		return;
+	}
+
+	DBG(dev, "suspend\n");
+}
+
+static void gmidi_resume(struct usb_gadget *gadget)
+{
+	struct gmidi_device *dev = get_gadget_data(gadget);
+
+	DBG(dev, "resume\n");
+}
+
+
+static struct usb_gadget_driver gmidi_driver = {
+	.speed		= USB_SPEED_FULL,
+	.function	= (char *)longname,
+	.bind		= gmidi_bind,
+	.unbind		= __exit_p(gmidi_unbind),
+
+	.setup		= gmidi_setup,
+	.disconnect	= gmidi_disconnect,
+
+	.suspend	= gmidi_suspend,
+	.resume		= gmidi_resume,
+
+	.driver 	= {
+		.name		= (char *)shortname,
+		.owner		= THIS_MODULE,
+	},
+};
+
+static int __init gmidi_init(void)
+{
+	/* a real value would likely come through some id prom
+	 * or module option.  this one takes at least two packets.
+	 */
+	strlcpy(serial, "0123456789.0123456789.0123456789", sizeof serial);
+
+	return usb_gadget_register_driver(&gmidi_driver);
+}
+module_init(gmidi_init);
+
+static void __exit gmidi_cleanup(void)
+{
+	usb_gadget_unregister_driver(&gmidi_driver);
+}
+module_exit(gmidi_cleanup);
+
diff --git a/include/linux/usb_audio.h b/include/linux/usb_audio.h
new file mode 100644
index 0000000..997f915
--- /dev/null
+++ b/include/linux/usb_audio.h
@@ -0,0 +1,52 @@
+/*
+ * <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 USB_AC_HEADER_DESCRIPTOR(n) {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubtype;				\
+	__le16 bcdADC;						\
+	__le16 wTotalLength;					\
+	__u8  bInCollection;					\
+	__u8  baInterfaceNr[n];					\
+} __attribute__ ((packed))
+
+#endif
diff --git a/include/linux/usb_midi.h b/include/linux/usb_midi.h
new file mode 100644
index 0000000..86b630c
--- /dev/null
+++ b/include/linux/usb_midi.h
@@ -0,0 +1,110 @@
+/*
+ * <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 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 USB_MS_ENDPOINT_DESCRIPTOR(n) {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubtype;				\
+	__u8  bNumEmbMIDIJack;					\
+	__u8  baAssocJackID[n];					\
+} __attribute__ ((packed))
+
+#endif
-- 
1.4.0



[-- Attachment #3: Type: text/plain, Size: 300 bytes --]

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[-- Attachment #4: Type: text/plain, Size: 191 bytes --]

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Re: [RFC] g_midi: New USB MIDI Gadget class driver.

[Clemens Ladisch]

Ben Williamson wrote:
> This patch adds a USB MIDI Gadget driver. This driver is glue between
> the USB gadget interface and the ALSA MIDI interface.

Looks good.  (Not that I tested it.  ;-)

Some remarks below.

> +config USB_MIDI_GADGET
> +	tristate "MIDI Gadget (EXPERIMENTAL)"
> +	depends on EXPERIMENTAL

You need something like this:
	depends on SND
	select SND_RAWMIDI

> +#include <sound/asequencer.h>

This header isn't needed.

> +	card = snd_card_new(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1, THIS_MODULE, 0);

Other ALSA drivers have module options for index and id.

I could imagine that a synthesizer has another sound card for PCM
output; it would make sense for at least the index to be configurable.

> +enomem:
> +	...
> +	return -ENOMEM;

These error handlers could return err instead.


Regards,
Clemens

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Re: [RFC] g_midi: New USB MIDI Gadget class driver.

[David Brownell]

On Wednesday 05 July 2006 11:06 pm, Ben Williamson wrote:

> Included are usb_audio.h and usb_midi.h containing definitions from
> the relevant USB specifications for USB audio and USB MIDI devices.
> The definitions of struct usb_ms_header_descriptor and struct
> usb_ms_endpoint_descriptor are the same as those that appear in
> sound/usb/usbmidi.c, with the intention of that file including
> <linux/usb_midi.h> instead. I have not included that change here.

Make that <linux/usb/midi.h> or maybe <linux/usb/audio.h> ... in
fact, several pending patches move <linux/usb_*.h> files into that
subdirectory, so watch out when this is ready to submit.

Glad to see such a driver.  I won't comment on the MIDI bits, but
quick comments on other parts are below.

- Dave



This still have some debris left over from gadget zero, like mentions
of having two configurations, using endpoint names rather than just
the endpoints, and even comments describing itself as being gadget zero. 
Best to clean that stuff up more; gadget zero did a bunch of stuff
mostly to make sure that APIs get tested, or to work with earlier
versions of the gadget framework, and your driver can be smaller.

I don't think this is a case where usb_ep_alloc_buffer() and friends
are desired ... such buffers are normally not cacheable.

You should have driver code to support high speed controllers, e.g. the
high speed descriptors including the device qualifier.


> +static const struct USB_MIDI_OUT_JACK_DESCRIPTOR(1) jack_out_emb_desc = {

What's with the SHOUTING in a struct name?  Those are nasty macros.
All the struct names should be lowercase.


Note that this attachment got mangled a bit too (STATE_SYSEX_2 line wrapped).


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Re: [RFC] g_midi: New USB MIDI Gadget class driver.

[Ben Williamson]

Clemens Ladisch wrote:
> You need something like this:
> 	depends on SND
> 	select SND_RAWMIDI

Thanks, will do.

>> +	card = snd_card_new(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1, THIS_MODULE, 0);
> 
> Other ALSA drivers have module options for index and id.

How's this?

static int index = SNDRV_DEFAULT_IDX1;
static char *id = SNDRV_DEFAULT_STR1;

module_param(index, int, 0444);
MODULE_PARM_DESC(index, "Index value for the USB MIDI Gadget adapter.");
module_param(id, charp, 0444);
MODULE_PARM_DESC(id, "ID string for the USB MIDI Gadget adapter.");

	card = snd_card_new(index, id, THIS_MODULE, 0);

I see lots of drivers with arrays for those, but I think I can use the excuse that
there is at most once instance of gmidi. As far as I can tell, the gadget subsystem
only handles one udc interface, at least for now.

Thanks for the feedback, I'll post another version when I can incorporating all the
suggestions.

Cheers,

- Ben.



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Re: [RFC] g_midi: New USB MIDI Gadget class driver.

[David Brownell]

> I see lots of drivers with arrays for those, but I think I can use the excuse that
> there is at most once instance of gmidi. As far as I can tell, the gadget subsystem
> only handles one udc interface, at least for now.

One UDC, yes -- that's a very basic USB definition thing.  But surely one
MIDI gadget can support multiple channels, one interface each?

- Dave


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Re: [RFC] g_midi: New USB MIDI Gadget class driver.

[Ben Williamson]

David Brownell wrote:
> One UDC, yes -- that's a very basic USB definition thing.  But surely one
> MIDI gadget can support multiple channels, one interface each?

Actually I was wondering if you plan to support plugging in multiple NetChip UDC
cards, but I can't imagine it would be all that useful.

At this stage g_midi only support one MIDI in jack and one MIDI out jack, because
that's all I need for now. In order to support more than that one would need to
add more jack descriptors and corresponding rawmidi substreams, none of which
should be too tough. But I think it would make the most sense for all that to
still appear under the one ALSA "card", with a single index and id as Clemens
suggested, at least as I understand it.

- Ben.

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