1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * ALSA sequencer MIDI-through client
4 * Copyright (c) 1999-2000 by Takashi Iwai <tiwai@suse.de>
7 #include <linux/init.h>
8 #include <linux/slab.h>
9 #include <linux/module.h>
10 #include <sound/core.h>
11 #include "seq_clientmgr.h"
12 #include <sound/initval.h>
13 #include <sound/asoundef.h>
17 Sequencer MIDI-through client
19 This gives a simple midi-through client. All the normal input events
20 are redirected to output port immediately.
21 The routing can be done via aconnect program in alsa-utils.
23 Each client has a static client number 14 (= SNDRV_SEQ_CLIENT_DUMMY).
24 If you want to auto-load this module, you may add the following alias
25 in your /etc/conf.modules file.
27 alias snd-seq-client-14 snd-seq-dummy
29 The module is loaded on demand for client 14, or /proc/asound/seq/
30 is accessed. If you don't need this module to be loaded, alias
31 snd-seq-client-14 as "off". This will help modprobe.
33 The number of ports to be created can be specified via the module
34 parameter "ports". For example, to create four ports, add the
35 following option in a configuration file under /etc/modprobe.d/:
37 option snd-seq-dummy ports=4
39 The model option "duplex=1" enables duplex operation to the port.
40 In duplex mode, a pair of ports are created instead of single port,
41 and events are tunneled between pair-ports. For example, input to
42 port A is sent to output port of another port B and vice versa.
43 In duplex mode, each port has DUPLEX capability.
48 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
49 MODULE_DESCRIPTION("ALSA sequencer MIDI-through client");
50 MODULE_LICENSE("GPL");
51 MODULE_ALIAS("snd-seq-client-" __stringify(SNDRV_SEQ_CLIENT_DUMMY));
56 module_param(ports, int, 0444);
57 MODULE_PARM_DESC(ports, "number of ports to be created");
58 module_param(duplex, bool, 0444);
59 MODULE_PARM_DESC(duplex, "create DUPLEX ports");
61 struct snd_seq_dummy_port {
68 static int my_client = -1;
71 * event input callback - just redirect events to subscribers
74 dummy_input(struct snd_seq_event *ev, int direct, void *private_data,
77 struct snd_seq_dummy_port *p;
78 struct snd_seq_event tmpev;
81 if (ev->source.client == SNDRV_SEQ_CLIENT_SYSTEM ||
82 ev->type == SNDRV_SEQ_EVENT_KERNEL_ERROR)
83 return 0; /* ignore system messages */
86 tmpev.source.port = p->connect;
88 tmpev.source.port = p->port;
89 tmpev.dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
90 return snd_seq_kernel_client_dispatch(p->client, &tmpev, atomic, hop);
94 * free_private callback
97 dummy_free(void *private_data)
105 static struct snd_seq_dummy_port __init *
106 create_port(int idx, int type)
108 struct snd_seq_port_info pinfo;
109 struct snd_seq_port_callback pcb;
110 struct snd_seq_dummy_port *rec;
112 rec = kzalloc(sizeof(*rec), GFP_KERNEL);
116 rec->client = my_client;
117 rec->duplex = duplex;
119 memset(&pinfo, 0, sizeof(pinfo));
120 pinfo.addr.client = my_client;
122 sprintf(pinfo.name, "Midi Through Port-%d:%c", idx,
125 sprintf(pinfo.name, "Midi Through Port-%d", idx);
126 pinfo.capability = SNDRV_SEQ_PORT_CAP_READ | SNDRV_SEQ_PORT_CAP_SUBS_READ;
127 pinfo.capability |= SNDRV_SEQ_PORT_CAP_WRITE | SNDRV_SEQ_PORT_CAP_SUBS_WRITE;
129 pinfo.capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
130 pinfo.type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
131 | SNDRV_SEQ_PORT_TYPE_SOFTWARE
132 | SNDRV_SEQ_PORT_TYPE_PORT;
133 memset(&pcb, 0, sizeof(pcb));
134 pcb.owner = THIS_MODULE;
135 pcb.event_input = dummy_input;
136 pcb.private_free = dummy_free;
137 pcb.private_data = rec;
139 if (snd_seq_kernel_client_ctl(my_client, SNDRV_SEQ_IOCTL_CREATE_PORT, &pinfo) < 0) {
143 rec->port = pinfo.addr.port;
148 * register client and create ports
151 register_client(void)
153 struct snd_seq_dummy_port *rec1, *rec2;
157 pr_err("ALSA: seq_dummy: invalid number of ports %d\n", ports);
162 my_client = snd_seq_create_kernel_client(NULL, SNDRV_SEQ_CLIENT_DUMMY,
168 for (i = 0; i < ports; i++) {
169 rec1 = create_port(i, 0);
171 snd_seq_delete_kernel_client(my_client);
175 rec2 = create_port(i, 1);
177 snd_seq_delete_kernel_client(my_client);
180 rec1->connect = rec2->port;
181 rec2->connect = rec1->port;
189 * delete client if exists
195 snd_seq_delete_kernel_client(my_client);
202 static int __init alsa_seq_dummy_init(void)
204 return register_client();
207 static void __exit alsa_seq_dummy_exit(void)
212 module_init(alsa_seq_dummy_init)
213 module_exit(alsa_seq_dummy_exit)