1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * ALSA sequencer MIDI-through client 4 * Copyright (c) 1999-2000 by Takashi Iwai <tiwai@suse.de> 5 */ 6 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> 14 15 /* 16 17 Sequencer MIDI-through client 18 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. 22 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. 26 27 alias snd-seq-client-14 snd-seq-dummy 28 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. 32 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/: 36 37 option snd-seq-dummy ports=4 38 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. 44 45 */ 46 47 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)); 52 53 static int ports = 1; 54 static bool duplex; 55 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"); 60 61 struct snd_seq_dummy_port { 62 int client; 63 int port; 64 int duplex; 65 int connect; 66 }; 67 68 static int my_client = -1; 69 70 /* 71 * event input callback - just redirect events to subscribers 72 */ 73 static int 74 dummy_input(struct snd_seq_event *ev, int direct, void *private_data, 75 int atomic, int hop) 76 { 77 struct snd_seq_dummy_port *p; 78 struct snd_seq_event tmpev; 79 80 p = private_data; 81 if (ev->source.client == SNDRV_SEQ_CLIENT_SYSTEM || 82 ev->type == SNDRV_SEQ_EVENT_KERNEL_ERROR) 83 return 0; /* ignore system messages */ 84 tmpev = *ev; 85 if (p->duplex) 86 tmpev.source.port = p->connect; 87 else 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); 91 } 92 93 /* 94 * free_private callback 95 */ 96 static void 97 dummy_free(void *private_data) 98 { 99 kfree(private_data); 100 } 101 102 /* 103 * create a port 104 */ 105 static struct snd_seq_dummy_port __init * 106 create_port(int idx, int type) 107 { 108 struct snd_seq_port_info pinfo; 109 struct snd_seq_port_callback pcb; 110 struct snd_seq_dummy_port *rec; 111 112 rec = kzalloc(sizeof(*rec), GFP_KERNEL); 113 if (!rec) 114 return NULL; 115 116 rec->client = my_client; 117 rec->duplex = duplex; 118 rec->connect = 0; 119 memset(&pinfo, 0, sizeof(pinfo)); 120 pinfo.addr.client = my_client; 121 if (duplex) 122 sprintf(pinfo.name, "Midi Through Port-%d:%c", idx, 123 (type ? 'B' : 'A')); 124 else 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; 128 if (duplex) 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; 138 pinfo.kernel = &pcb; 139 if (snd_seq_kernel_client_ctl(my_client, SNDRV_SEQ_IOCTL_CREATE_PORT, &pinfo) < 0) { 140 kfree(rec); 141 return NULL; 142 } 143 rec->port = pinfo.addr.port; 144 return rec; 145 } 146 147 /* 148 * register client and create ports 149 */ 150 static int __init 151 register_client(void) 152 { 153 struct snd_seq_dummy_port *rec1, *rec2; 154 int i; 155 156 if (ports < 1) { 157 pr_err("ALSA: seq_dummy: invalid number of ports %d\n", ports); 158 return -EINVAL; 159 } 160 161 /* create client */ 162 my_client = snd_seq_create_kernel_client(NULL, SNDRV_SEQ_CLIENT_DUMMY, 163 "Midi Through"); 164 if (my_client < 0) 165 return my_client; 166 167 /* create ports */ 168 for (i = 0; i < ports; i++) { 169 rec1 = create_port(i, 0); 170 if (rec1 == NULL) { 171 snd_seq_delete_kernel_client(my_client); 172 return -ENOMEM; 173 } 174 if (duplex) { 175 rec2 = create_port(i, 1); 176 if (rec2 == NULL) { 177 snd_seq_delete_kernel_client(my_client); 178 return -ENOMEM; 179 } 180 rec1->connect = rec2->port; 181 rec2->connect = rec1->port; 182 } 183 } 184 185 return 0; 186 } 187 188 /* 189 * delete client if exists 190 */ 191 static void __exit 192 delete_client(void) 193 { 194 if (my_client >= 0) 195 snd_seq_delete_kernel_client(my_client); 196 } 197 198 /* 199 * Init part 200 */ 201 202 static int __init alsa_seq_dummy_init(void) 203 { 204 return register_client(); 205 } 206 207 static void __exit alsa_seq_dummy_exit(void) 208 { 209 delete_client(); 210 } 211 212 module_init(alsa_seq_dummy_init) 213 module_exit(alsa_seq_dummy_exit) 214