ALSA: MIDI driver for Behringer BCD2000 USB device

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.
Signed-off-by: Mario Kicherer <dev@kicherer.org>
Reviewed-by: Daniel Mack <daniel@zonque.org>
Reviewed-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/Kconfig

@@ -147,5 +147,18 @@ 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
 

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/

sound/usb/bcd2000/Makefile

+snd-bcd2000-y := bcd2000.o
+
+obj-$(CONFIG_SND_BCD2000) += snd-bcd2000.o
\ No newline at end of file

sound/usb/bcd2000/bcd2000.c

+/*
+ * 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 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;
+}
+
+/* (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 = ACCESS_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 = ACCESS_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 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;
+
+	/* 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);
+
+	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");