linux/sound/core/seq/seq_dummy.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ALSA sequencer MIDI-through client
 * Copyright (c) 1999-2000 by Takashi Iwai <[email protected]>
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <sound/core.h>
#include "seq_clientmgr.h"
#include <sound/initval.h>
#include <sound/asoundef.h>

/*

  Sequencer MIDI-through client

  This gives a simple midi-through client.  All the normal input events
  are redirected to output port immediately.
  The routing can be done via aconnect program in alsa-utils.

  Each client has a static client number 14 (= SNDRV_SEQ_CLIENT_DUMMY).
  If you want to auto-load this module, you may add the following alias
  in your /etc/conf.modules file.

	alias snd-seq-client-14  snd-seq-dummy

  The module is loaded on demand for client 14, or /proc/asound/seq/
  is accessed.  If you don't need this module to be loaded, alias
  snd-seq-client-14 as "off".  This will help modprobe.

  The number of ports to be created can be specified via the module
  parameter "ports".  For example, to create four ports, add the
  following option in a configuration file under /etc/modprobe.d/:

	option snd-seq-dummy ports=4

  The model option "duplex=1" enables duplex operation to the port.
  In duplex mode, a pair of ports are created instead of single port,
  and events are tunneled between pair-ports.  For example, input to
  port A is sent to output port of another port B and vice versa.
  In duplex mode, each port has DUPLEX capability.

 */


MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;
MODULE_ALIAS(…) …;

static int ports = …;
static bool duplex;

module_param(ports, int, 0444);
MODULE_PARM_DESC(…) …;
module_param(duplex, bool, 0444);
MODULE_PARM_DESC(…) …;

#if IS_ENABLED(CONFIG_SND_SEQ_UMP)
static int ump;
module_param(ump, int, 0444);
MODULE_PARM_DESC(…) …;
#endif

struct snd_seq_dummy_port { … };

static int my_client = …;

/*
 * event input callback - just redirect events to subscribers
 */
static int
dummy_input(struct snd_seq_event *ev, int direct, void *private_data,
	    int atomic, int hop)
{ … }

/*
 * free_private callback
 */
static void
dummy_free(void *private_data)
{ … }

/*
 * create a port
 */
static struct snd_seq_dummy_port __init *
create_port(int idx, int type)
{ … }

/*
 * register client and create ports
 */
static int __init
register_client(void)
{ … }

/*
 * delete client if exists
 */
static void __exit
delete_client(void)
{ … }

/*
 *  Init part
 */

static int __init alsa_seq_dummy_init(void)
{ … }

static void __exit alsa_seq_dummy_exit(void)
{ … }

module_init(…) …
module_exit(…)