/*
 * 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/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";

/*
 * We can only handle 16 cables on one single endpoint, as cable numbers are
 * stored in 4-bit fields. And as the interface currently only holds one
 * single endpoint, this is the maximum number of ports we can allow.
 */
#define MAX_PORTS 16

/*
 * 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;
        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[MAX_PORTS];
        struct snd_rawmidi_substream *out_substream[MAX_PORTS];
        struct gmidi_in_port    *in_port[MAX_PORTS];

        unsigned long           out_triggered;
        struct tasklet_struct   tasklet;
        unsigned int in_ports;
        unsigned int out_ports;
        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(16);

/* 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 =      DYNAMIC */
};

/* 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 struct usb_ms_endpoint_descriptor_16 ms_out_desc = {
        /* .bLength =           DYNAMIC */
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   USB_MS_GENERAL,
        /* .bNumEmbMIDIJack =   DYNAMIC */
        /* .baAssocJackID =     DYNAMIC */
};

/* 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 struct usb_ms_endpoint_descriptor_16 ms_in_desc = {
        /* .bLength =           DYNAMIC */
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   USB_MS_GENERAL,
        /* .bNumEmbMIDIJack =   DYNAMIC */
        /* .baAssocJackID =     DYNAMIC */
};

/* 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;
        struct snd_rawmidi_substream *substream = midi->out_substream[cable];

        if (!substream)
                /* Nobody is listening - throw it on the floor. */
                return;

        if (!test_bit(cable, &midi->out_triggered))
                return;

        snd_rawmidi_receive(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_all_descriptors(f);
        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 << 4;

        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;
        int i;

        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;

        for (i = 0; i < MAX_PORTS; i++) {
                struct gmidi_in_port *port = midi->in_port[i];
                struct snd_rawmidi_substream *substream = midi->in_substream[i];

                if (!port || !port->active || !substream)
                        continue;

                while (req->length + 3 < midi->buflen) {
                        uint8_t b;
                        if (snd_rawmidi_transmit(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;

        if (!midi->in_port[substream->number])
                return -EINVAL;

        VDBG(midi, "%s()\n", __func__);
        midi->in_substream[substream->number] = substream;
        midi->in_port[substream->number]->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;

        if (!midi->in_port[substream->number])
                return;

        VDBG(midi, "%s() %d\n", __func__, up);
        midi->in_port[substream->number]->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;

        if (substream->number >= MAX_PORTS)
                return -EINVAL;

        VDBG(midi, "%s()\n", __func__);
        midi->out_substream[substream->number] = 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;
        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 */
        snd_component_add(card, "MIDI");
        err = snd_rawmidi_new(card, card->longname, 0,
                              midi->out_ports, midi->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_descriptor_header **midi_function;
        struct usb_midi_in_jack_descriptor jack_in_ext_desc[MAX_PORTS];
        struct usb_midi_in_jack_descriptor jack_in_emb_desc[MAX_PORTS];
        struct usb_midi_out_jack_descriptor_1 jack_out_ext_desc[MAX_PORTS];
        struct usb_midi_out_jack_descriptor_1 jack_out_emb_desc[MAX_PORTS];
        struct usb_composite_dev *cdev = c->cdev;
        struct f_midi *midi = func_to_midi(f);
        int status, n, jack = 1, i = 0;

        /* 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 */

        /* allocate temporary function list */
        midi_function = kcalloc((MAX_PORTS * 4) + 9, sizeof(*midi_function),
                                GFP_KERNEL);
        if (!midi_function) {
                status = -ENOMEM;
                goto fail;
        }

        /*
         * construct the function's descriptor set. As the number of
         * input and output MIDI ports is configurable, we have to do
         * it that way.
         */

        /* add the headers - these are always the same */
        midi_function[i++] = (struct usb_descriptor_header *) &ac_interface_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ac_header_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_interface_desc;

        /* calculate the header's wTotalLength */
        n = USB_DT_MS_HEADER_SIZE
                + (midi->in_ports + midi->out_ports) *
                        (USB_DT_MIDI_IN_SIZE + USB_DT_MIDI_OUT_SIZE(1));
        ms_header_desc.wTotalLength = cpu_to_le16(n);

        midi_function[i++] = (struct usb_descriptor_header *) &ms_header_desc;

        /* configure the external IN jacks, each linked to an embedded OUT jack */
        for (n = 0; n < midi->in_ports; n++) {
                struct usb_midi_in_jack_descriptor *in_ext = &jack_in_ext_desc[n];
                struct usb_midi_out_jack_descriptor_1 *out_emb = &jack_out_emb_desc[n];

                in_ext->bLength                 = USB_DT_MIDI_IN_SIZE;
                in_ext->bDescriptorType         = USB_DT_CS_INTERFACE;
                in_ext->bDescriptorSubtype      = USB_MS_MIDI_IN_JACK;
                in_ext->bJackType               = USB_MS_EXTERNAL;
                in_ext->bJackID                 = jack++;
                in_ext->iJack                   = 0;
                midi_function[i++] = (struct usb_descriptor_header *) in_ext;

                out_emb->bLength                = USB_DT_MIDI_OUT_SIZE(1);
                out_emb->bDescriptorType        = USB_DT_CS_INTERFACE;
                out_emb->bDescriptorSubtype     = USB_MS_MIDI_OUT_JACK;
                out_emb->bJackType              = USB_MS_EMBEDDED;
                out_emb->bJackID                = jack++;
                out_emb->bNrInputPins           = 1;
                out_emb->pins[0].baSourcePin    = 1;
                out_emb->pins[0].baSourceID     = in_ext->bJackID;
                out_emb->iJack                  = 0;
                midi_function[i++] = (struct usb_descriptor_header *) out_emb;

                /* link it to the endpoint */
                ms_in_desc.baAssocJackID[n] = out_emb->bJackID;
        }

        /* configure the external OUT jacks, each linked to an embedded IN jack */
        for (n = 0; n < midi->out_ports; n++) {
                struct usb_midi_in_jack_descriptor *in_emb = &jack_in_emb_desc[n];
                struct usb_midi_out_jack_descriptor_1 *out_ext = &jack_out_ext_desc[n];

                in_emb->bLength                 = USB_DT_MIDI_IN_SIZE;
                in_emb->bDescriptorType         = USB_DT_CS_INTERFACE;
                in_emb->bDescriptorSubtype      = USB_MS_MIDI_IN_JACK;
                in_emb->bJackType               = USB_MS_EMBEDDED;
                in_emb->bJackID                 = jack++;
                in_emb->iJack                   = 0;
                midi_function[i++] = (struct usb_descriptor_header *) in_emb;

                out_ext->bLength =              USB_DT_MIDI_OUT_SIZE(1);
                out_ext->bDescriptorType =      USB_DT_CS_INTERFACE;
                out_ext->bDescriptorSubtype =   USB_MS_MIDI_OUT_JACK;
                out_ext->bJackType =            USB_MS_EXTERNAL;
                out_ext->bJackID =              jack++;
                out_ext->bNrInputPins =         1;
                out_ext->iJack =                0;
                out_ext->pins[0].baSourceID =   in_emb->bJackID;
                out_ext->pins[0].baSourcePin =  1;
                midi_function[i++] = (struct usb_descriptor_header *) out_ext;

                /* link it to the endpoint */
                ms_out_desc.baAssocJackID[n] = in_emb->bJackID;
        }

        /* configure the endpoint descriptors ... */
        ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
        ms_out_desc.bNumEmbMIDIJack = midi->in_ports;

        ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
        ms_in_desc.bNumEmbMIDIJack = midi->out_ports;

        /* ... and add them to the list */
        midi_function[i++] = (struct usb_descriptor_header *) &bulk_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &bulk_in_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_in_desc;
        midi_function[i++] = NULL;

        /*
         * 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 */
        f->fs_descriptors = usb_copy_descriptors(midi_function);
        if (!f->fs_descriptors)
                goto fail_f_midi;

        if (gadget_is_dualspeed(c->cdev->gadget)) {
                bulk_in_desc.wMaxPacketSize = cpu_to_le16(512);
                bulk_out_desc.wMaxPacketSize = cpu_to_le16(512);
                f->hs_descriptors = usb_copy_descriptors(midi_function);
                if (!f->hs_descriptors)
                        goto fail_f_midi;
        }

        kfree(midi_function);

        return 0;

fail_f_midi:
        kfree(midi_function);
        usb_free_descriptors(f->hs_descriptors);
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 in_ports,
                              unsigned int out_ports,
                              unsigned int buflen,
                              unsigned int qlen)
{
        struct f_midi *midi;
        int status, i;

        /* sanity check */
        if (in_ports > MAX_PORTS || out_ports > MAX_PORTS)
                return -EINVAL;

        /* allocate and initialize one new instance */
        midi = kzalloc(sizeof *midi, GFP_KERNEL);
        if (!midi) {
                status = -ENOMEM;
                goto fail;
        }

        for (i = 0; i < in_ports; i++) {
                struct gmidi_in_port *port = kzalloc(sizeof(*port), GFP_KERNEL);
                if (!port) {
                        status = -ENOMEM;
                        goto setup_fail;
                }

                port->midi = midi;
                port->active = 0;
                port->cable = i;
                midi->in_port[i] = port;
        }

        midi->gadget = c->cdev->gadget;
        tasklet_init(&midi->tasklet, f_midi_in_tasklet, (unsigned long) midi);

        /* set up ALSA midi devices */
        midi->in_ports = in_ports;
        midi->out_ports = out_ports;
        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:
        for (--i; i >= 0; i--)
                kfree(midi->in_port[i]);
        kfree(midi);
fail:
        return status;
}