USB: gadget: midi: add midi function driver

This patch adds f_midi.c to implement a USB gadget function that works
with the composite framework, so it can be combined with other USB
functions.

The code for the ALSA/MIDI logic was taken from the midi device gadget,
other parts have been rewritten to benefit from the dynamic descriptor
allocation features.

This was successfully tested on an OMAP3 board.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 923 insertions, 0 deletions

diff --git a/drivers/usb/gadget/f_midi.c b/drivers/usb/gadget/f_midi.c
new file mode 100644
index 000000000000..5064ea4efbed
--- /dev/null
+++ b/drivers/usb/gadget/f_midi.c
@@ -0,0 +1,923 @@
+/*
+ * f_midi.c -- USB MIDI class function driver
+ *
+ * Copyright (C) 2006 Thumtronics Pty Ltd.
+ * Developed for Thumtronics by Grey Innovation
+ * Ben Williamson <ben.williamson@greyinnovation.com>
+ *
+ * Rewritten for the composite framework
+ *   Copyright (C) 2011 Daniel Mack <zonque@gmail.com>
+ *
+ * Based on drivers/usb/gadget/f_audio.c,
+ *   Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
+ *   Copyright (C) 2008 Analog Devices, Inc
+ *
+ * and drivers/usb/gadget/midi.c,
+ *   Copyright (C) 2006 Thumtronics Pty Ltd.
+ *   Ben Williamson <ben.williamson@greyinnovation.com>
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/utsname.h>
+#include <linux/device.h>
+
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/rawmidi.h>
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/audio.h>
+#include <linux/usb/midi.h>
+
+MODULE_AUTHOR("Ben Williamson");
+MODULE_LICENSE("GPL v2");
+
+static const char f_midi_shortname[] = "f_midi";
+static const char f_midi_longname[] = "MIDI Gadget";
+
+/*
+ * 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 f_midi *midi;
+	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 f_midi {
+	struct usb_function	func;
+	struct usb_gadget	*gadget;
+	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;
+	int index;
+	char *id;
+	unsigned int buflen, qlen;
+};
+
+static inline struct f_midi *func_to_midi(struct usb_function *f)
+{
+	return container_of(f, struct f_midi, func);
+}
+
+static void f_midi_transmit(struct f_midi *midi, struct usb_request *req);
+
+DECLARE_UAC_AC_HEADER_DESCRIPTOR(1);
+DECLARE_USB_MIDI_OUT_JACK_DESCRIPTOR(1);
+DECLARE_USB_MS_ENDPOINT_DESCRIPTOR(1);
+
+/* B.3.1  Standard AC Interface Descriptor */
+static struct usb_interface_descriptor ac_interface_desc __initdata = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	/* .bInterfaceNumber =	DYNAMIC */
+	/* .bNumEndpoints =	DYNAMIC */
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOCONTROL,
+	/* .iInterface =	DYNAMIC */
+};
+
+/* B.3.2  Class-Specific AC Interface Descriptor */
+static struct uac1_ac_header_descriptor_1 ac_header_desc __initdata = {
+	.bLength =		UAC_DT_AC_HEADER_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_HEADER,
+	.bcdADC =		cpu_to_le16(0x0100),
+	.wTotalLength =		cpu_to_le16(UAC_DT_AC_HEADER_SIZE(1)),
+	.bInCollection =	1,
+	/* .baInterfaceNr =	DYNAMIC */
+};
+
+/* B.4.1  Standard MS Interface Descriptor */
+static struct usb_interface_descriptor ms_interface_desc __initdata = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	/* .bInterfaceNumber =	DYNAMIC */
+	.bNumEndpoints =	2,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_MIDISTREAMING,
+	/* .iInterface =	DYNAMIC */
+};
+
+/* B.4.2  Class-Specific MS Interface Descriptor */
+static struct usb_ms_header_descriptor ms_header_desc __initdata = {
+	.bLength =		USB_DT_MS_HEADER_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	USB_MS_HEADER,
+	.bcdMSC =		cpu_to_le16(0x0100),
+	.wTotalLength =		cpu_to_le16(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 struct usb_descriptor_header *midi_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,
+};
+
+/* string IDs are assigned dynamically */
+
+#define STRING_FUNC_IDX			0
+
+static struct usb_string midi_string_defs[] = {
+	[STRING_FUNC_IDX].s = "MIDI function",
+	{  } /* end of list */
+};
+
+static struct usb_gadget_strings midi_stringtab = {
+	.language	= 0x0409,	/* en-us */
+	.strings	= midi_string_defs,
+};
+
+static struct usb_gadget_strings *midi_strings[] = {
+	&midi_stringtab,
+	NULL,
+};
+
+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 = kmalloc(length, 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)
+{
+	kfree(req->buf);
+	usb_ep_free_request(ep, req);
+}
+
+static const uint8_t f_midi_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 f_midi_read_data(struct usb_ep *ep, int cable,
+			     uint8_t *data, int length)
+{
+	struct f_midi *midi = ep->driver_data;
+	/* cable is ignored, because for now we only have one. */
+
+	if (!midi->out_substream)
+		/* Nobody is listening - throw it on the floor. */
+		return;
+
+	if (!test_bit(midi->out_substream->number, &midi->out_triggered))
+		return;
+
+	snd_rawmidi_receive(midi->out_substream, data, length);
+}
+
+static void f_midi_handle_out_data(struct usb_ep *ep, struct usb_request *req)
+{
+	unsigned int 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 = f_midi_cin_length[buf[i] & 0x0f];
+			f_midi_read_data(ep, cable, &buf[i + 1], length);
+		}
+}
+
+static void
+f_midi_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_midi *midi = ep->driver_data;
+	struct usb_composite_dev *cdev = midi->func.config->cdev;
+	int status = req->status;
+
+	switch (status) {
+	case 0:			 /* normal completion */
+		if (ep == midi->out_ep) {
+			/* We received stuff. req is queued again, below */
+			f_midi_handle_out_data(ep, req);
+		} else if (ep == midi->in_ep) {
+			/* Our transmit completed. See if there's more to go.
+			 * f_midi_transmit eats req, don't queue it again. */
+			f_midi_transmit(midi, 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(cdev, "%s gone (%d), %d/%d\n", ep->name, status,
+				req->actual, req->length);
+		if (ep == midi->out_ep)
+			f_midi_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(cdev, "%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(cdev, "kill %s:  resubmit %d bytes --> %d\n",
+				ep->name, req->length, status);
+		usb_ep_set_halt(ep);
+		/* FIXME recover later ... somehow */
+	}
+}
+
+static int f_midi_start_ep(struct f_midi *midi,
+			   struct usb_function *f,
+			   struct usb_ep *ep)
+{
+	int err;
+	struct usb_composite_dev *cdev = f->config->cdev;
+
+	if (ep->driver_data)
+		usb_ep_disable(ep);
+
+	err = config_ep_by_speed(midi->gadget, f, ep);
+	if (err) {
+		ERROR(cdev, "can't configure %s: %d\n", ep->name, err);
+		return err;
+	}
+
+	err = usb_ep_enable(ep);
+	if (err) {
+		ERROR(cdev, "can't start %s: %d\n", ep->name, err);
+		return err;
+	}
+
+	ep->driver_data = midi;
+
+	return 0;
+}
+
+static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+	struct f_midi *midi = func_to_midi(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+	unsigned i;
+	int err;
+
+	err = f_midi_start_ep(midi, f, midi->in_ep);
+	if (err)
+		return err;
+
+	err = f_midi_start_ep(midi, f, midi->out_ep);
+	if (err)
+		return err;
+
+	if (midi->out_ep->driver_data)
+		usb_ep_disable(midi->out_ep);
+
+	err = config_ep_by_speed(midi->gadget, f, midi->out_ep);
+	if (err) {
+		ERROR(cdev, "can't configure %s: %d\n",
+		      midi->out_ep->name, err);
+		return err;
+	}
+
+	err = usb_ep_enable(midi->out_ep);
+	if (err) {
+		ERROR(cdev, "can't start %s: %d\n",
+		      midi->out_ep->name, err);
+		return err;
+	}
+
+	midi->out_ep->driver_data = midi;
+
+	/* allocate a bunch of read buffers and queue them all at once. */
+	for (i = 0; i < midi->qlen && err == 0; i++) {
+		struct usb_request *req =
+			alloc_ep_req(midi->out_ep, midi->buflen);
+		if (req == NULL)
+			return -ENOMEM;
+
+		req->complete = f_midi_complete;
+		err = usb_ep_queue(midi->out_ep, req, GFP_ATOMIC);
+		if (err) {
+			ERROR(midi, "%s queue req: %d\n",
+				    midi->out_ep->name, err);
+		}
+	}
+
+	return 0;
+}
+
+static void f_midi_disable(struct usb_function *f)
+{
+	struct f_midi *midi = func_to_midi(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+
+	DBG(cdev, "disable\n");
+
+	/*
+	 * just disable endpoints, forcing completion of pending i/o.
+	 * all our completion handlers free their requests in this case.
+	 */
+	usb_ep_disable(midi->in_ep);
+	usb_ep_disable(midi->out_ep);
+}
+
+static void f_midi_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev *cdev = f->config->cdev;
+	struct f_midi *midi = func_to_midi(f);
+	struct snd_card *card;
+
+	DBG(cdev, "unbind\n");
+
+	/* just to be sure */
+	f_midi_disable(f);
+
+	card = midi->card;
+	midi->card = NULL;
+	if (card)
+		snd_card_free(card);
+
+	kfree(midi->id);
+	midi->id = NULL;
+
+	usb_free_descriptors(f->descriptors);
+	kfree(midi);
+}
+
+static int f_midi_snd_free(struct snd_device *device)
+{
+	return 0;
+}
+
+static void f_midi_transmit_packet(struct usb_request *req, uint8_t p0,
+					uint8_t p1, uint8_t p2, uint8_t p3)
+{
+	unsigned length = req->length;
+	u8 *buf = (u8 *)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 f_midi_transmit_byte(struct usb_request *req,
+				 struct gmidi_in_port *port, uint8_t b)
+{
+	uint8_t p0 = port->cable;
+
+	if (b >= 0xf8) {
+		f_midi_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:
+			f_midi_transmit_packet(req, p0 | 0x05, 0xf6, 0, 0);
+			port->state = STATE_UNKNOWN;
+			break;
+		case 0xf7:
+			switch (port->state) {
+			case STATE_SYSEX_0:
+				f_midi_transmit_packet(req,
+					p0 | 0x05, 0xf7, 0, 0);
+				break;
+			case STATE_SYSEX_1:
+				f_midi_transmit_packet(req,
+					p0 | 0x06, port->data[0], 0xf7, 0);
+				break;
+			case STATE_SYSEX_2:
+				f_midi_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;
+			}
+			f_midi_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;
+			}
+			f_midi_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:
+			f_midi_transmit_packet(req,
+				p0 | 0x04, port->data[0], port->data[1], b);
+			port->state = STATE_SYSEX_0;
+			break;
+		}
+	}
+}
+
+static void f_midi_transmit(struct f_midi *midi, struct usb_request *req)
+{
+	struct usb_ep *ep = midi->in_ep;
+	struct gmidi_in_port *port = &midi->in_port;
+
+	if (!ep)
+		return;
+
+	if (!req)
+		req = alloc_ep_req(ep, midi->buflen);
+
+	if (!req) {
+		ERROR(midi, "gmidi_transmit: alloc_ep_request failed\n");
+		return;
+	}
+	req->length = 0;
+	req->complete = f_midi_complete;
+
+	if (port->active) {
+		while (req->length + 3 < midi->buflen) {
+			uint8_t b;
+			if (snd_rawmidi_transmit(midi->in_substream, &b, 1) != 1) {
+				port->active = 0;
+				break;
+			}
+			f_midi_transmit_byte(req, port, b);
+		}
+	}
+
+	if (req->length > 0)
+		usb_ep_queue(ep, req, GFP_ATOMIC);
+	else
+		free_ep_req(ep, req);
+}
+
+static void f_midi_in_tasklet(unsigned long data)
+{
+	struct f_midi *midi = (struct f_midi *) data;
+	f_midi_transmit(midi, NULL);
+}
+
+static int f_midi_in_open(struct snd_rawmidi_substream *substream)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s()\n", __func__);
+	midi->in_substream = substream;
+	midi->in_port.state = STATE_UNKNOWN;
+	return 0;
+}
+
+static int f_midi_in_close(struct snd_rawmidi_substream *substream)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s()\n", __func__);
+	return 0;
+}
+
+static void f_midi_in_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s() %d\n", __func__, up);
+	midi->in_port.active = up;
+	if (up)
+		tasklet_hi_schedule(&midi->tasklet);
+}
+
+static int f_midi_out_open(struct snd_rawmidi_substream *substream)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s()\n", __func__);
+	midi->out_substream = substream;
+	return 0;
+}
+
+static int f_midi_out_close(struct snd_rawmidi_substream *substream)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s()\n", __func__);
+	return 0;
+}
+
+static void f_midi_out_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct f_midi *midi = substream->rmidi->private_data;
+
+	VDBG(midi, "%s()\n", __func__);
+
+	if (up)
+		set_bit(substream->number, &midi->out_triggered);
+	else
+		clear_bit(substream->number, &midi->out_triggered);
+}
+
+static struct snd_rawmidi_ops gmidi_in_ops = {
+	.open = f_midi_in_open,
+	.close = f_midi_in_close,
+	.trigger = f_midi_in_trigger,
+};
+
+static struct snd_rawmidi_ops gmidi_out_ops = {
+	.open = f_midi_out_open,
+	.close = f_midi_out_close,
+	.trigger = f_midi_out_trigger
+};
+
+/* register as a sound "card" */
+static int f_midi_register_card(struct f_midi *midi)
+{
+	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 = f_midi_snd_free,
+	};
+
+	err = snd_card_create(midi->index, midi->id, THIS_MODULE, 0, &card);
+	if (err < 0) {
+		ERROR(midi, "snd_card_create() failed\n");
+		goto fail;
+	}
+	midi->card = card;
+
+	err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, midi, &ops);
+	if (err < 0) {
+		ERROR(midi, "snd_device_new() failed: error %d\n", err);
+		goto fail;
+	}
+
+	strcpy(card->driver, f_midi_longname);
+	strcpy(card->longname, f_midi_longname);
+	strcpy(card->shortname, f_midi_shortname);
+
+	/* Set up rawmidi */
+	midi->in_port.midi = midi;
+	midi->in_port.active = 0;
+	snd_component_add(card, "MIDI");
+	err = snd_rawmidi_new(card, card->longname, 0,
+			      out_ports, in_ports, &rmidi);
+	if (err < 0) {
+		ERROR(midi, "snd_rawmidi_new() failed: error %d\n", err);
+		goto fail;
+	}
+	midi->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 = midi;
+
+	/*
+	 * 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, &midi->gadget->dev);
+
+	/* register it - we're ready to go */
+	err = snd_card_register(card);
+	if (err < 0) {
+		ERROR(midi, "snd_card_register() failed\n");
+		goto fail;
+	}
+
+	VDBG(midi, "%s() finished ok\n", __func__);
+	return 0;
+
+fail:
+	if (midi->card) {
+		snd_card_free(midi->card);
+		midi->card = NULL;
+	}
+	return err;
+}
+
+/* MIDI function driver setup/binding */
+
+static int __init
+f_midi_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	struct f_midi *midi = func_to_midi(f);
+	int status;
+
+	/* maybe allocate device-global string ID */
+	if (midi_string_defs[0].id == 0) {
+		status = usb_string_id(c->cdev);
+		if (status < 0)
+			goto fail;
+		midi_string_defs[0].id = status;
+	}
+
+	/* We have two interfaces, AudioControl and MIDIStreaming */
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	ac_interface_desc.bInterfaceNumber = status;
+
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	ms_interface_desc.bInterfaceNumber = status;
+	ac_header_desc.baInterfaceNr[0] = status;
+
+	status = -ENODEV;
+
+	/* allocate instance-specific endpoints */
+	midi->in_ep = usb_ep_autoconfig(cdev->gadget, &bulk_in_desc);
+	if (!midi->in_ep)
+		goto fail;
+	midi->in_ep->driver_data = cdev;	/* claim */
+
+	midi->out_ep = usb_ep_autoconfig(cdev->gadget, &bulk_out_desc);
+	if (!midi->out_ep)
+		goto fail;
+	midi->out_ep->driver_data = cdev;	/* claim */
+
+	/*
+	 * support all relevant hardware speeds... we expect that when
+	 * hardware is dual speed, all bulk-capable endpoints work at
+	 * both speeds
+	 */
+	/* copy descriptors, and track endpoint copies */
+	if (gadget_is_dualspeed(c->cdev->gadget)) {
+		c->highspeed = true;
+		bulk_in_desc.wMaxPacketSize = cpu_to_le16(512);
+		bulk_out_desc.wMaxPacketSize = cpu_to_le16(512);
+		f->hs_descriptors = usb_copy_descriptors(midi_function);
+	} else {
+		f->descriptors = usb_copy_descriptors(midi_function);
+	}
+
+	return 0;
+
+fail:
+	/* we might as well release our claims on endpoints */
+	if (midi->out_ep)
+		midi->out_ep->driver_data = NULL;
+	if (midi->in_ep)
+		midi->in_ep->driver_data = NULL;
+
+	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
+
+	return status;
+}
+
+/**
+ * f_midi_bind_config - add USB MIDI function to a configuration
+ * @c: the configuration to supcard the USB audio function
+ * @index: the soundcard index to use for the ALSA device creation
+ * @id: the soundcard id to use for the ALSA device creation
+ * @buflen: the buffer length to use
+ * @qlen the number of read requests to pre-allocate
+ * Context: single threaded during gadget setup
+ *
+ * Returns zero on success, else negative errno.
+ */
+int __init f_midi_bind_config(struct usb_configuration *c,
+			      int index, char *id,
+			      unsigned int buflen,
+			      unsigned int qlen)
+{
+	struct f_midi *midi;
+	int status;
+
+	/* allocate and initialize one new instance */
+	midi = kzalloc(sizeof *midi, GFP_KERNEL);
+	if (!midi) {
+		status = -ENOMEM;
+		goto fail;
+	}
+
+	midi->gadget = c->cdev->gadget;
+	tasklet_init(&midi->tasklet, f_midi_in_tasklet, (unsigned long) midi);
+
+	/* set up ALSA midi devices */
+	status = f_midi_register_card(midi);
+	if (status < 0)
+		goto setup_fail;
+
+	midi->func.name        = "gmidi function";
+	midi->func.strings     = midi_strings;
+	midi->func.bind        = f_midi_bind;
+	midi->func.unbind      = f_midi_unbind;
+	midi->func.set_alt     = f_midi_set_alt;
+	midi->func.disable     = f_midi_disable;
+
+	midi->id = kstrdup(id, GFP_KERNEL);
+	midi->index = index;
+	midi->buflen = buflen;
+	midi->qlen = qlen;
+
+	status = usb_add_function(c, &midi->func);
+	if (status)
+		goto setup_fail;
+
+	return 0;
+
+setup_fail:
+	kfree(midi);
+fail:
+	return status;
+}
+