/*
 * Behringer BCD2000 driver
 *
 *   Copyright (C) 2014 Mario Kicherer (dev@kicherer.org)
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 */

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

static 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;

	strlcpy(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 not necessary, urb is aborted automatically */

	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;

	mutex_lock(&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) {
		mutex_unlock(&devices_mutex);
		return -ENOENT;
	}

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

	strncpy(card->driver, "snd-bcd2000", sizeof(card->driver));
	strncpy(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);

	mutex_unlock(&devices_mutex);
	return 0;

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

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

	if (!bcd2k)
		return;

	mutex_lock(&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);

	mutex_unlock(&devices_mutex);
}

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");