seq_system.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *   ALSA sequencer System services Client
  4 *   Copyright (c) 1998-1999 by Frank van de Pol <fvdpol@coil.demon.nl>
  5 */
  6
  7#include <linux/init.h>
  8#include <linux/export.h>
  9#include <linux/slab.h>
 10#include <sound/core.h>
 11#include "seq_system.h"
 12#include "seq_timer.h"
 13#include "seq_queue.h"
 14
 15/* internal client that provide system services, access to timer etc. */
 16
 17/*
 18 * Port "Timer"
 19 *      - send tempo /start/stop etc. events to this port to manipulate the 
 20 *        queue's timer. The queue address is specified in
 21 *	  data.queue.queue.
 22 *      - this port supports subscription. The received timer events are 
 23 *        broadcasted to all subscribed clients. The modified tempo
 24 *	  value is stored on data.queue.value.
 25 *	  The modifier client/port is not send.
 26 *
 27 * Port "Announce"
 28 *      - does not receive message
 29 *      - supports supscription. For each client or port attaching to or 
 30 *        detaching from the system an announcement is send to the subscribed
 31 *        clients.
 32 *
 33 * Idea: the subscription mechanism might also work handy for distributing 
 34 * synchronisation and timing information. In this case we would ideally have
 35 * a list of subscribers for each type of sync (time, tick), for each timing
 36 * queue.
 37 *
 38 * NOTE: the queue to be started, stopped, etc. must be specified
 39 *	 in data.queue.addr.queue field.  queue is used only for
 40 *	 scheduling, and no longer referred as affected queue.
 41 *	 They are used only for timer broadcast (see above).
 42 *							-- iwai
 43 */
 44
 45
 46/* client id of our system client */
 47static int sysclient = -1;
 48
 49/* port id numbers for this client */
 50static int announce_port = -1;
 51
 52/* number of subscriptions to announce port */
 53static int announce_subscribed;
 54
 55
 56/* fill standard header data, source port & channel are filled in */
 57static int setheader(struct snd_seq_event * ev, int client, int port)
 58{
 59	if (announce_port < 0 || !announce_subscribed)
 60		return -ENODEV;
 61
 62	memset(ev, 0, sizeof(struct snd_seq_event));
 63
 64	ev->flags &= ~SNDRV_SEQ_EVENT_LENGTH_MASK;
 65	ev->flags |= SNDRV_SEQ_EVENT_LENGTH_FIXED;
 66
 67	ev->source.client = sysclient;
 68	ev->source.port = announce_port;
 69	ev->dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
 70
 71	/* fill data */
 72	/*ev->data.addr.queue = SNDRV_SEQ_ADDRESS_UNKNOWN;*/
 73	ev->data.addr.client = client;
 74	ev->data.addr.port = port;
 75
 76	return 0;
 77}
 78
 79
 80/* entry points for broadcasting system events */
 81void snd_seq_system_broadcast(int client, int port, int type, bool atomic)
 82{
 83	struct snd_seq_event ev;
 84	
 85	if (setheader(&ev, client, port) < 0)
 86		return;
 87	ev.type = type;
 88	snd_seq_kernel_client_dispatch(sysclient, &ev, atomic, 0);
 89}
 90EXPORT_SYMBOL_GPL(snd_seq_system_broadcast);
 91
 92/* entry points for broadcasting system events */
 93int snd_seq_system_notify(int client, int port, struct snd_seq_event *ev,
 94			  bool atomic)
 95{
 96	ev->flags = SNDRV_SEQ_EVENT_LENGTH_FIXED;
 97	ev->source.client = sysclient;
 98	ev->source.port = announce_port;
 99	ev->dest.client = client;
100	ev->dest.port = port;
101	return snd_seq_kernel_client_dispatch(sysclient, ev, atomic, 0);
102}
103
104/* call-back handler for timer events */
105static int event_input_timer(struct snd_seq_event * ev, int direct, void *private_data, int atomic, int hop)
106{
107	return snd_seq_control_queue(ev, atomic, hop);
108}
109
110static int sys_announce_subscribe(void *private_data,
111				  struct snd_seq_port_subscribe *info)
112{
113	announce_subscribed++;
114	return 0;
115}
116
117static int sys_announce_unsubscribe(void *private_data,
118				    struct snd_seq_port_subscribe *info)
119{
120	if (snd_BUG_ON(!announce_subscribed))
121		return 0;
122	announce_subscribed--;
123	return 0;
124}
125
126/* register our internal client */
127int __init snd_seq_system_client_init(void)
128{
129	struct snd_seq_port_callback pcallbacks;
130	struct snd_seq_port_info *port;
131	int err;
132
133	port = kzalloc(sizeof(*port), GFP_KERNEL);
134	if (!port)
135		return -ENOMEM;
136
137	memset(&pcallbacks, 0, sizeof(pcallbacks));
138	pcallbacks.owner = THIS_MODULE;
139	pcallbacks.event_input = event_input_timer;
140
141	/* register client */
142	sysclient = snd_seq_create_kernel_client(NULL, 0, "System");
143	if (sysclient < 0) {
144		kfree(port);
145		return sysclient;
146	}
147
148	/* register timer */
149	strscpy(port->name, "Timer");
150	port->capability = SNDRV_SEQ_PORT_CAP_WRITE; /* accept queue control */
151	port->capability |= SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ; /* for broadcast */
152	port->kernel = &pcallbacks;
153	port->type = 0;
154	port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
155	port->addr.client = sysclient;
156	port->addr.port = SNDRV_SEQ_PORT_SYSTEM_TIMER;
157	err = snd_seq_kernel_client_ctl(sysclient, SNDRV_SEQ_IOCTL_CREATE_PORT,
158					port);
159	if (err < 0)
160		goto error_port;
161
162	/* register announcement port */
163	strscpy(port->name, "Announce");
164	port->capability = SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ; /* for broadcast only */
165	pcallbacks.event_input = NULL;
166	pcallbacks.subscribe = sys_announce_subscribe;
167	pcallbacks.unsubscribe = sys_announce_unsubscribe;
168	port->kernel = &pcallbacks;
169	port->type = 0;
170	port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
171	port->addr.client = sysclient;
172	port->addr.port = SNDRV_SEQ_PORT_SYSTEM_ANNOUNCE;
173	err = snd_seq_kernel_client_ctl(sysclient, SNDRV_SEQ_IOCTL_CREATE_PORT,
174					port);
175	if (err < 0)
176		goto error_port;
177	announce_port = port->addr.port;
178
179	kfree(port);
180	return 0;
181
182 error_port:
183	snd_seq_system_client_done();
184	kfree(port);
185	return err;
186}
187
188
189/* unregister our internal client */
190void snd_seq_system_client_done(void)
191{
192	int oldsysclient = sysclient;
193
194	if (oldsysclient >= 0) {
195		sysclient = -1;
196		announce_port = -1;
197		snd_seq_delete_kernel_client(oldsysclient);
198	}
199}