// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Behringer BCD2000 driver
 *
 *   Copyright (C) 2014 Mario Kicherer (dev@kicherer.org)
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/bitmap.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <sound/core.h>
#include <sound/initval.h>
#include <sound/rawmidi.h>

#define PREFIX "snd-bcd2000: "
#define BUFSIZE 64

static const struct usb_device_id id_table[] = {
        { USB_DEVICE(0x1397, 0x00bd) },
        { },
};

static const unsigned char device_cmd_prefix[] = {0x03, 0x00};

static const unsigned char bcd2000_init_sequence[] = {
        0x07, 0x00, 0x00, 0x00, 0x78, 0x48, 0x1c, 0x81,
        0xc4, 0x00, 0x00, 0x00, 0x5e, 0x53, 0x4a, 0xf7,
        0x18, 0xfa, 0x11, 0xff, 0x6c, 0xf3, 0x90, 0xff,
        0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
        0x18, 0xfa, 0x11, 0xff, 0x14, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0xf2, 0x34, 0x4a, 0xf7,
        0x18, 0xfa, 0x11, 0xff
};

struct bcd2000 {
        struct usb_device *dev;
        struct snd_card *card;
        struct usb_interface *intf;
        int card_index;

        int midi_out_active;
        struct snd_rawmidi *rmidi;
        struct snd_rawmidi_substream *midi_receive_substream;
        struct snd_rawmidi_substream *midi_out_substream;

        unsigned char midi_in_buf[BUFSIZE];
        unsigned char midi_out_buf[BUFSIZE];

        struct urb *midi_out_urb;
        struct urb *midi_in_urb;

        struct usb_anchor anchor;
};

static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;

static DEFINE_MUTEX(devices_mutex);
static DECLARE_BITMAP(devices_used, SNDRV_CARDS);
static struct usb_driver bcd2000_driver;

#ifdef CONFIG_SND_DEBUG
static void bcd2000_dump_buffer(const char *prefix, const char *buf, int len)
{
        print_hex_dump(KERN_DEBUG, prefix,
                        DUMP_PREFIX_NONE, 16, 1,
                        buf, len, false);
}
#else
static void bcd2000_dump_buffer(const char *prefix, const char *buf, int len) {}
#endif

static int bcd2000_midi_input_open(struct snd_rawmidi_substream *substream)
{
        return 0;
}

static int bcd2000_midi_input_close(struct snd_rawmidi_substream *substream)
{
        return 0;
}

/* (de)register midi substream from client */
static void bcd2000_midi_input_trigger(struct snd_rawmidi_substream *substream,
                                                int up)
{
        struct bcd2000 *bcd2k = substream->rmidi->private_data;
        bcd2k->midi_receive_substream = up ? substream : NULL;
}

static void bcd2000_midi_handle_input(struct bcd2000 *bcd2k,
                                const unsigned char *buf, unsigned int buf_len)
{
        unsigned int payload_length, tocopy;
        struct snd_rawmidi_substream *midi_receive_substream;

        midi_receive_substream = READ_ONCE(bcd2k->midi_receive_substream);
        if (!midi_receive_substream)
                return;

        bcd2000_dump_buffer(PREFIX "received from device: ", buf, buf_len);

        if (buf_len < 2)
                return;

        payload_length = buf[0];

        /* ignore packets without payload */
        if (payload_length == 0)
                return;

        tocopy = min(payload_length, buf_len-1);

        bcd2000_dump_buffer(PREFIX "sending to userspace: ",
                                        &buf[1], tocopy);

        snd_rawmidi_receive(midi_receive_substream,
                                        &buf[1], tocopy);
}

static void bcd2000_midi_send(struct bcd2000 *bcd2k)
{
        int len, ret;
        struct snd_rawmidi_substream *midi_out_substream;

        BUILD_BUG_ON(sizeof(device_cmd_prefix) >= BUFSIZE);

        midi_out_substream = READ_ONCE(bcd2k->midi_out_substream);
        if (!midi_out_substream)
                return;

        /* copy command prefix bytes */
        memcpy(bcd2k->midi_out_buf, device_cmd_prefix,
                sizeof(device_cmd_prefix));

        /*
         * get MIDI packet and leave space for command prefix
         * and payload length
         */
        len = snd_rawmidi_transmit(midi_out_substream,
                                bcd2k->midi_out_buf + 3, BUFSIZE - 3);

        if (len < 0)
                dev_err(&bcd2k->dev->dev, "%s: snd_rawmidi_transmit error %d\n",
                                __func__, len);

        if (len <= 0)
                return;

        /* set payload length */
        bcd2k->midi_out_buf[2] = len;
        bcd2k->midi_out_urb->transfer_buffer_length = BUFSIZE;

        bcd2000_dump_buffer(PREFIX "sending to device: ",
                        bcd2k->midi_out_buf, len+3);

        /* send packet to the BCD2000 */
        ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_ATOMIC);
        if (ret < 0)
                dev_err(&bcd2k->dev->dev, PREFIX
                        "%s (%p): usb_submit_urb() failed, ret=%d, len=%d\n",
                        __func__, midi_out_substream, ret, len);
        else
                bcd2k->midi_out_active = 1;
}

static int bcd2000_midi_output_open(struct snd_rawmidi_substream *substream)
{
        return 0;
}

static int bcd2000_midi_output_close(struct snd_rawmidi_substream *substream)
{
        struct bcd2000 *bcd2k = substream->rmidi->private_data;

        if (bcd2k->midi_out_active) {
                usb_kill_urb(bcd2k->midi_out_urb);
                bcd2k->midi_out_active = 0;
        }

        return 0;
}

/* (de)register midi substream from client */
static void bcd2000_midi_output_trigger(struct snd_rawmidi_substream *substream,
                                                int up)
{
        struct bcd2000 *bcd2k = substream->rmidi->private_data;

        if (up) {
                bcd2k->midi_out_substream = substream;
                /* check if there is data userspace wants to send */
                if (!bcd2k->midi_out_active)
                        bcd2000_midi_send(bcd2k);
        } else {
                bcd2k->midi_out_substream = NULL;
        }
}

static void bcd2000_output_complete(struct urb *urb)
{
        struct bcd2000 *bcd2k = urb->context;

        bcd2k->midi_out_active = 0;

        if (urb->status)
                dev_warn(&urb->dev->dev,
                        PREFIX "output urb->status: %d\n", urb->status);

        if (urb->status == -ESHUTDOWN)
                return;

        /* check if there is more data userspace wants to send */
        bcd2000_midi_send(bcd2k);
}

static void bcd2000_input_complete(struct urb *urb)
{
        int ret;
        struct bcd2000 *bcd2k = urb->context;

        if (urb->status)
                dev_warn(&urb->dev->dev,
                        PREFIX "input urb->status: %i\n", urb->status);

        if (!bcd2k || urb->status == -ESHUTDOWN)
                return;

        if (urb->actual_length > 0)
                bcd2000_midi_handle_input(bcd2k, urb->transfer_buffer,
                                        urb->actual_length);

        /* return URB to device */
        ret = usb_submit_urb(bcd2k->midi_in_urb, GFP_ATOMIC);
        if (ret < 0)
                dev_err(&bcd2k->dev->dev, PREFIX
                        "%s: usb_submit_urb() failed, ret=%d\n",
                        __func__, ret);
}

static const struct snd_rawmidi_ops bcd2000_midi_output = {
        .open =    bcd2000_midi_output_open,
        .close =   bcd2000_midi_output_close,
        .trigger = bcd2000_midi_output_trigger,
};

static const struct snd_rawmidi_ops bcd2000_midi_input = {
        .open =    bcd2000_midi_input_open,
        .close =   bcd2000_midi_input_close,
        .trigger = bcd2000_midi_input_trigger,
};

static void bcd2000_init_device(struct bcd2000 *bcd2k)
{
        int ret;

        init_usb_anchor(&bcd2k->anchor);
        usb_anchor_urb(bcd2k->midi_out_urb, &bcd2k->anchor);
        usb_anchor_urb(bcd2k->midi_in_urb, &bcd2k->anchor);

        /* copy init sequence into buffer */
        memcpy(bcd2k->midi_out_buf, bcd2000_init_sequence, 52);
        bcd2k->midi_out_urb->transfer_buffer_length = 52;

        /* submit sequence */
        ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_KERNEL);
        if (ret < 0)
                dev_err(&bcd2k->dev->dev, PREFIX
                        "%s: usb_submit_urb() out failed, ret=%d: ",
                        __func__, ret);
        else
                bcd2k->midi_out_active = 1;

        /* pass URB to device to enable button and controller events */
        ret = usb_submit_urb(bcd2k->midi_in_urb, GFP_KERNEL);
        if (ret < 0)
                dev_err(&bcd2k->dev->dev, PREFIX
                        "%s: usb_submit_urb() in failed, ret=%d: ",
                        __func__, ret);

        /* ensure initialization is finished */
        usb_wait_anchor_empty_timeout(&bcd2k->anchor, 1000);
}

static int bcd2000_init_midi(struct bcd2000 *bcd2k)
{
        int ret;
        struct snd_rawmidi *rmidi;

        ret = snd_rawmidi_new(bcd2k->card, bcd2k->card->shortname, 0,
                                        1, /* output */
                                        1, /* input */
                                        &rmidi);

        if (ret < 0)
                return ret;

        strscpy(rmidi->name, bcd2k->card->shortname, sizeof(rmidi->name));

        rmidi->info_flags = SNDRV_RAWMIDI_INFO_DUPLEX;
        rmidi->private_data = bcd2k;

        rmidi->info_flags |= SNDRV_RAWMIDI_INFO_OUTPUT;
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
                                        &bcd2000_midi_output);

        rmidi->info_flags |= SNDRV_RAWMIDI_INFO_INPUT;
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT,
                                        &bcd2000_midi_input);

        bcd2k->rmidi = rmidi;

        bcd2k->midi_in_urb = usb_alloc_urb(0, GFP_KERNEL);
        bcd2k->midi_out_urb = usb_alloc_urb(0, GFP_KERNEL);

        if (!bcd2k->midi_in_urb || !bcd2k->midi_out_urb) {
                dev_err(&bcd2k->dev->dev, PREFIX "usb_alloc_urb failed\n");
                return -ENOMEM;
        }

        usb_fill_int_urb(bcd2k->midi_in_urb, bcd2k->dev,
                                usb_rcvintpipe(bcd2k->dev, 0x81),
                                bcd2k->midi_in_buf, BUFSIZE,
                                bcd2000_input_complete, bcd2k, 1);

        usb_fill_int_urb(bcd2k->midi_out_urb, bcd2k->dev,
                                usb_sndintpipe(bcd2k->dev, 0x1),
                                bcd2k->midi_out_buf, BUFSIZE,
                                bcd2000_output_complete, bcd2k, 1);

        /* sanity checks of EPs before actually submitting */
        if (usb_urb_ep_type_check(bcd2k->midi_in_urb) ||
            usb_urb_ep_type_check(bcd2k->midi_out_urb)) {
                dev_err(&bcd2k->dev->dev, "invalid MIDI EP\n");
                return -EINVAL;
        }

        bcd2000_init_device(bcd2k);

        return 0;
}

static void bcd2000_free_usb_related_resources(struct bcd2000 *bcd2k,
                                                struct usb_interface *interface)
{
        usb_kill_urb(bcd2k->midi_out_urb);
        usb_kill_urb(bcd2k->midi_in_urb);

        usb_free_urb(bcd2k->midi_out_urb);
        usb_free_urb(bcd2k->midi_in_urb);

        if (bcd2k->intf) {
                usb_set_intfdata(bcd2k->intf, NULL);
                bcd2k->intf = NULL;
        }
}

static int bcd2000_probe(struct usb_interface *interface,
                                const struct usb_device_id *usb_id)
{
        struct snd_card *card;
        struct bcd2000 *bcd2k;
        unsigned int card_index;
        char usb_path[32];
        int err;

        guard(mutex)(&devices_mutex);

        for (card_index = 0; card_index < SNDRV_CARDS; ++card_index)
                if (!test_bit(card_index, devices_used))
                        break;

        if (card_index >= SNDRV_CARDS)
                return -ENOENT;

        err = snd_card_new(&interface->dev, index[card_index], id[card_index],
                        THIS_MODULE, sizeof(*bcd2k), &card);
        if (err < 0)
                return err;

        bcd2k = card->private_data;
        bcd2k->dev = interface_to_usbdev(interface);
        bcd2k->card = card;
        bcd2k->card_index = card_index;
        bcd2k->intf = interface;

        snd_card_set_dev(card, &interface->dev);

        strscpy(card->driver, "snd-bcd2000", sizeof(card->driver));
        strscpy(card->shortname, "BCD2000", sizeof(card->shortname));
        usb_make_path(bcd2k->dev, usb_path, sizeof(usb_path));
        snprintf(bcd2k->card->longname, sizeof(bcd2k->card->longname),
                    "Behringer BCD2000 at %s",
                        usb_path);

        err = bcd2000_init_midi(bcd2k);
        if (err < 0)
                goto probe_error;

        err = snd_card_register(card);
        if (err < 0)
                goto probe_error;

        usb_set_intfdata(interface, bcd2k);
        set_bit(card_index, devices_used);

        return 0;

probe_error:
        dev_info(&bcd2k->dev->dev, PREFIX "error during probing");
        bcd2000_free_usb_related_resources(bcd2k, interface);
        snd_card_free(card);
        return err;
}

static void bcd2000_disconnect(struct usb_interface *interface)
{
        struct bcd2000 *bcd2k = usb_get_intfdata(interface);

        if (!bcd2k)
                return;

        guard(mutex)(&devices_mutex);

        /* make sure that userspace cannot create new requests */
        snd_card_disconnect(bcd2k->card);

        bcd2000_free_usb_related_resources(bcd2k, interface);

        clear_bit(bcd2k->card_index, devices_used);

        snd_card_free_when_closed(bcd2k->card);
}

static struct usb_driver bcd2000_driver = {
        .name =         "snd-bcd2000",
        .probe =        bcd2000_probe,
        .disconnect =   bcd2000_disconnect,
        .id_table =     id_table,
};

module_usb_driver(bcd2000_driver);

MODULE_DEVICE_TABLE(usb, id_table);
MODULE_AUTHOR("Mario Kicherer, dev@kicherer.org");
MODULE_DESCRIPTION("Behringer BCD2000 driver");
MODULE_LICENSE("GPL");