[v6] MIDI driver for Behringer BCD2000 USB device
diff mbox

Message ID 1392909089-6242-1-git-send-email-dev@kicherer.org
State Changes Requested
Delegated to: Takashi Iwai
Headers show

Commit Message

Mario Kicherer Feb. 20, 2014, 3:11 p.m. UTC
This patch adds initial support for the Behringer BCD2000 USB DJ controller.
At the moment, only the MIDI part of the device is working, i.e. knobs,
buttons and LEDs.

I also plan to add support for the audio part, but I assume that this will
require more effort than the rather simple MIDI interface. Progress can be
tracked at https://github.com/anyc/snd-usb-bcd2000.

Changes since v5:
	- use kernel bitmap functions for devices_used

Changes since v4:
	- devices_used as array to support arbitrary number of SNDRV_CARDS
	- removed unused array "enable"

Changes since v3:
        - applied style and snd_printk changes as suggested by Daniel Mack

Changes since v2:
        - applied more changes from Daniel Mack and Clemens Ladisch

Changes since v1:
        - fixed the various code style issues, thanks to Daniel Mack and
          checkpatch.pl.

Signed-off-by: Mario Kicherer <dev@kicherer.org>
---
 sound/usb/Kconfig           |  13 ++
 sound/usb/Makefile          |   2 +-
 sound/usb/bcd2000/Makefile  |   3 +
 sound/usb/bcd2000/bcd2000.c | 488 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 505 insertions(+), 1 deletion(-)
 create mode 100644 sound/usb/bcd2000/Makefile
 create mode 100644 sound/usb/bcd2000/bcd2000.c

Comments

Clemens Ladisch Feb. 23, 2014, 8:24 p.m. UTC | #1
Mario Kicherer wrote:
> +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
> +};

I wonder how much of this is the actual init sequence, and how much is
random garbage.  :-)

> +	/*
> +	 * Packet structure: mm nn oo (pp)
> +	 *	mm: payload length
> +	 *	nn: MIDI command or note
> +	 *	oo: note or velocity
> +	 *	pp: velocity

The device often sends data as single-byte packets, so the structure
actually is "length data...".

> +	/* copy the "set LED" command bytes */
> +	memcpy(bcd2k->midi_out_buf, device_cmd_prefix,
> +		sizeof(device_cmd_prefix));

This is also used for data request and input selection, so it's not
"set LED" but just "MIDI output".

> +static void bcd2000_input_complete(struct urb *urb)
> +{
> +	if (urb->status) {
> +		dev_warn(dev, PREFIX "input urb->status: %i\n", urb->status);
> +		return;
> +	}

This will stop the input even on transient errors.

> +	/* acknowledge received packet */
> +	ret = usb_submit_urb(bcd2k->midi_in_urb, GFP_ATOMIC);
> +	if (ret < 0)
> +		dev_err(dev, "unable to submit urb. OOM!?\n");

Don't guess, just show ret.  :)

> +	strcpy(card->driver, DEVICE_NAME);
> +	strcpy(card->shortname, DEVICE_SHORTNAME);
> +	usb_make_path(bcd2k->dev, usb_path, sizeof(usb_path));
> +	snprintf(bcd2k->card->longname, sizeof(bcd2k->card->longname),
> +			DEVICE_NAME ", at %s",
> +			usb_path);

$ cat /proc/asound/cards
...
18 [bcd2000        ]: Behringer BCD200bcd2000 - bcd2000
                      Behringer BCD2000, at usb-0000:00:13.1-3

The driver name just identifies the driver, it does not need the vendor
name.  (And it should not overflow its buffer.)

The short name is shown to the user in many places, so it should be
properly capitalized.

The long name does not need the comma.

> +	dev_info(&bcd2k->dev->dev, PREFIX "%s", bcd2k->card->longname);

What use does this message have in the log?


Regards,
Clemens
Mario Kicherer Feb. 24, 2014, 8:05 p.m. UTC | #2
On 23.02.2014 21:24, Clemens Ladisch wrote:
> I wonder how much of this is the actual init sequence, and how much is
> random garbage.  :-)

Me too, but I want to make sure the module works before I start 
experimenting and risk modifying/damaging my device. Some bytes in
between stay the same, some seem to change randomly everytime I plug in
the device.

> The device often sends data as single-byte packets, so the structure
> actually is "length data...".

Yeah, it's a bit misleading here. I'll change this part.

>> +static void bcd2000_input_complete(struct urb *urb)
>> +{
>> +	if (urb->status) {
>> +		dev_warn(dev, PREFIX "input urb->status: %i\n", urb->status);
>> +		return;
>> +	}
>
> This will stop the input even on transient errors.

Hm, so, it is important to send the "acknowledge" urb afterwards
nonetheless?

> $ cat /proc/asound/cards
> ...
> 18 [bcd2000        ]: Behringer BCD200bcd2000 - bcd2000
>                        Behringer BCD2000, at usb-0000:00:13.1-3
>
> The driver name just identifies the driver, it does not need the vendor
> name.  (And it should not overflow its buffer.)
>
> The short name is shown to the user in many places, so it should be
> properly capitalized.
>
> The long name does not need the comma.

I removed the macros and just placed the names in there directly as
that's the only place they're used anyway.

Do you actually own a BCD2000?

>> +	dev_info(&bcd2k->dev->dev, PREFIX "%s", bcd2k->card->longname);
>
> What use does this message have in the log?

I saw this in another driver and thought this is common practice. I'll
remove it then.

Thank you for your comments!
Mario
Clemens Ladisch Feb. 24, 2014, 8:39 p.m. UTC | #3
Mario Kicherer wrote:
> On 23.02.2014 21:24, Clemens Ladisch wrote:
>>> +static void bcd2000_input_complete(struct urb *urb)
>>> +{
>>> +    if (urb->status) {
>>> +        dev_warn(dev, PREFIX "input urb->status: %i\n", urb->status);
>>> +        return;
>>> +    }
>>
>> This will stop the input even on transient errors.
>
> Hm, so, it is important to send the "acknowledge" urb afterwards
> nonetheless?

This has nothing to do with acknowledging.  Once the completion callback
was called, the URB is again owned by your driver, and nothing happens
unless you submit it again.

The only reason not to re-submit the URB is a permanent error (i.e., if
the device has been unplugged).

> Do you actually own a BCD2000?

Yes.


Regards,
Clemens

Patch
diff mbox

diff --git a/sound/usb/Kconfig b/sound/usb/Kconfig
index de9408b..145653a 100644
--- a/sound/usb/Kconfig
+++ b/sound/usb/Kconfig
@@ -146,5 +146,18 @@  config SND_USB_HIFACE
 	  To compile this driver as a module, choose M here: the module
 	  will be called snd-usb-hiface.
 
+config SND_BCD2000
+	tristate "Behringer BCD2000 MIDI driver"
+	select SND_RAWMIDI
+	help
+	  Say Y here to include MIDI support for the Behringer BCD2000 DJ
+	  controller.
+
+	  Audio support is still work-in-progress at
+	  https://github.com/anyc/snd-usb-bcd2000
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called snd-bcd2000.
+
 endif	# SND_USB
 
diff --git a/sound/usb/Makefile b/sound/usb/Makefile
index abe668f..2b92f0d 100644
--- a/sound/usb/Makefile
+++ b/sound/usb/Makefile
@@ -23,4 +23,4 @@  obj-$(CONFIG_SND_USB_UA101) += snd-usbmidi-lib.o
 obj-$(CONFIG_SND_USB_USX2Y) += snd-usbmidi-lib.o
 obj-$(CONFIG_SND_USB_US122L) += snd-usbmidi-lib.o
 
-obj-$(CONFIG_SND) += misc/ usx2y/ caiaq/ 6fire/ hiface/
+obj-$(CONFIG_SND) += misc/ usx2y/ caiaq/ 6fire/ hiface/ bcd2000/
diff --git a/sound/usb/bcd2000/Makefile b/sound/usb/bcd2000/Makefile
new file mode 100644
index 0000000..f09ccc0
--- /dev/null
+++ b/sound/usb/bcd2000/Makefile
@@ -0,0 +1,3 @@ 
+snd-bcd2000-y := bcd2000.o
+
+obj-$(CONFIG_SND_BCD2000) += snd-bcd2000.o
\ No newline at end of file
diff --git a/sound/usb/bcd2000/bcd2000.c b/sound/usb/bcd2000/bcd2000.c
new file mode 100644
index 0000000..82d5e9d
--- /dev/null
+++ b/sound/usb/bcd2000/bcd2000.c
@@ -0,0 +1,488 @@ 
+/*
+ * 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 DEVICE_NAME "Behringer BCD2000"
+#define DEVICE_SHORTNAME "bcd2000"
+
+#define PREFIX DEVICE_SHORTNAME ": "
+#define BUFSIZE 64
+
+static 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);
+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;
+}
+
+/* register midi substream */
+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 len)
+{
+	unsigned int length, tocopy;
+	struct snd_rawmidi_substream *midi_receive_substream;
+
+	midi_receive_substream = ACCESS_ONCE(bcd2k->midi_receive_substream);
+	if (!midi_receive_substream)
+		return;
+
+	bcd2000_dump_buffer(PREFIX "received from device: ", buf, len);
+
+	if (len < 2)
+		return;
+
+	/*
+	 * Packet structure: mm nn oo (pp)
+	 *	mm: payload length
+	 *	nn: MIDI command or note
+	 *	oo: note or velocity
+	 *	pp: velocity
+	 */
+
+	length = buf[0];
+
+	/* ignore packets without payload */
+	if (length == 0)
+		return;
+
+	tocopy = min(length, 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,
+				struct snd_rawmidi_substream *substream)
+{
+	int len, ret;
+
+	BUILD_BUG_ON(sizeof(device_cmd_prefix) >= BUFSIZE);
+
+	/* copy the "set LED" command 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(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__, 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;
+}
+
+/* register midi substream */
+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, substream);
+	} else {
+		bcd2k->midi_out_substream = NULL;
+	}
+}
+
+static void bcd2000_output_complete(struct urb *urb)
+{
+	struct bcd2000 *bcd2k = urb->context;
+	struct snd_rawmidi_substream *midi_out_substream;
+
+	bcd2k->midi_out_active = 0;
+
+	if (urb->status != 0)
+		dev_err(&urb->dev->dev,
+			PREFIX "output urb->status: %d\n", urb->status);
+
+	midi_out_substream = ACCESS_ONCE(bcd2k->midi_out_substream);
+	if (!midi_out_substream)
+		return;
+
+	/* check if there is more data userspace wants to send */
+	bcd2000_midi_send(bcd2k, midi_out_substream);
+}
+
+static void bcd2000_input_complete(struct urb *urb)
+{
+	int ret;
+	struct device *dev = &urb->dev->dev;
+	struct bcd2000 *bcd2k = urb->context;
+
+	if (urb->status) {
+		dev_warn(dev, PREFIX "input urb->status: %i\n", urb->status);
+		return;
+	}
+
+	if (!bcd2k)
+		return;
+
+	if (urb->actual_length > 0)
+		bcd2000_midi_handle_input(bcd2k, urb->transfer_buffer,
+					urb->actual_length);
+
+	/* acknowledge received packet */
+	ret = usb_submit_urb(bcd2k->midi_in_urb, GFP_ATOMIC);
+	if (ret < 0)
+		dev_err(dev, "unable to submit urb. OOM!?\n");
+}
+
+static struct snd_rawmidi_ops bcd2000_midi_output = {
+	.open =    bcd2000_midi_output_open,
+	.close =   bcd2000_midi_output_close,
+	.trigger = bcd2000_midi_output_trigger,
+};
+
+static 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;
+
+	/* send empty packet 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);
+
+	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_create(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);
+
+	strcpy(card->driver, DEVICE_NAME);
+	strcpy(card->shortname, DEVICE_SHORTNAME);
+	usb_make_path(bcd2k->dev, usb_path, sizeof(usb_path));
+	snprintf(bcd2k->card->longname, sizeof(bcd2k->card->longname),
+			DEVICE_NAME ", at %s",
+			usb_path);
+
+	dev_info(&bcd2k->dev->dev, PREFIX "%s", bcd2k->card->longname);
+
+	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 =	DEVICE_SHORTNAME,
+	.probe =	bcd2000_probe,
+	.disconnect =	bcd2000_disconnect,
+	.id_table =	id_table,
+};
+
+static int __init bcd2000_init(void)
+{
+	int retval = 0;
+
+	retval = usb_register(&bcd2000_driver);
+	if (retval)
+		pr_info(PREFIX "usb_register failed. Error: %d", retval);
+	return retval;
+}
+
+static void __exit bcd2000_exit(void)
+{
+	usb_deregister(&bcd2000_driver);
+}
+
+module_init(bcd2000_init);
+module_exit(bcd2000_exit);
+
+MODULE_DEVICE_TABLE(usb, id_table);
+MODULE_AUTHOR("Mario Kicherer, dev@kicherer.org");
+MODULE_DESCRIPTION("Behringer BCD2000 driver");
+MODULE_LICENSE("GPL");