sound/core/seq/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 */
  47 static int sysclient = -1;
  48
  49 /* port id numbers for this client */
  50 static int announce_port = -1;
  51
  52
  53
  54 /* fill standard header data, source port & channel are filled in */
  55 static int setheader(struct snd_seq_event * ev, int client, int port)
  56 {
  57         if (announce_port < 0)
  58                 return -ENODEV;
  59
  60         memset(ev, 0, sizeof(struct snd_seq_event));
  61
  62         ev->flags &= ~SNDRV_SEQ_EVENT_LENGTH_MASK;
  63         ev->flags |= SNDRV_SEQ_EVENT_LENGTH_FIXED;
  64
  65         ev->source.client = sysclient;
  66         ev->source.port = announce_port;
  67         ev->dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
  68
  69         /* fill data */
  70         /*ev->data.addr.queue = SNDRV_SEQ_ADDRESS_UNKNOWN;*/
  71         ev->data.addr.client = client;
  72         ev->data.addr.port = port;
  73
  74         return 0;
  75 }
  76
  77
  78 /* entry points for broadcasting system events */
  79 void snd_seq_system_broadcast(int client, int port, int type)
  80 {
  81         struct snd_seq_event ev;
  82
  83         if (setheader(&ev, client, port) < 0)
  84                 return;
  85         ev.type = type;
  86         snd_seq_kernel_client_dispatch(sysclient, &ev, 0, 0);
  87 }
  88
  89 /* entry points for broadcasting system events */
  90 int snd_seq_system_notify(int client, int port, struct snd_seq_event *ev)
  91 {
  92         ev->flags = SNDRV_SEQ_EVENT_LENGTH_FIXED;
  93         ev->source.client = sysclient;
  94         ev->source.port = announce_port;
  95         ev->dest.client = client;
  96         ev->dest.port = port;
  97         return snd_seq_kernel_client_dispatch(sysclient, ev, 0, 0);
  98 }
  99
 100 /* call-back handler for timer events */
 101 static int event_input_timer(struct snd_seq_event * ev, int direct, void *private_data, int atomic, int hop)
 102 {
 103         return snd_seq_control_queue(ev, atomic, hop);
 104 }
 105
 106 /* register our internal client */
 107 int __init snd_seq_system_client_init(void)
 108 {
 109         struct snd_seq_port_callback pcallbacks;
 110         struct snd_seq_port_info *port;
 111         int err;
 112
 113         port = kzalloc(sizeof(*port), GFP_KERNEL);
 114         if (!port)
 115                 return -ENOMEM;
 116
 117         memset(&pcallbacks, 0, sizeof(pcallbacks));
 118         pcallbacks.owner = THIS_MODULE;
 119         pcallbacks.event_input = event_input_timer;
 120
 121         /* register client */
 122         sysclient = snd_seq_create_kernel_client(NULL, 0, "System");
 123         if (sysclient < 0) {
 124                 kfree(port);
 125                 return sysclient;
 126         }
 127
 128         /* register timer */
 129         strcpy(port->name, "Timer");
 130         port->capability = SNDRV_SEQ_PORT_CAP_WRITE; /* accept queue control */
 131         port->capability |= SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ; /* for broadcast */
 132         port->kernel = &pcallbacks;
 133         port->type = 0;
 134         port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
 135         port->addr.client = sysclient;
 136         port->addr.port = SNDRV_SEQ_PORT_SYSTEM_TIMER;
 137         err = snd_seq_kernel_client_ctl(sysclient, SNDRV_SEQ_IOCTL_CREATE_PORT,
 138                                         port);
 139         if (err < 0)
 140                 goto error_port;
 141
 142         /* register announcement port */
 143         strcpy(port->name, "Announce");
 144         port->capability = SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ; /* for broadcast only */
 145         port->kernel = NULL;
 146         port->type = 0;
 147         port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
 148         port->addr.client = sysclient;
 149         port->addr.port = SNDRV_SEQ_PORT_SYSTEM_ANNOUNCE;
 150         err = snd_seq_kernel_client_ctl(sysclient, SNDRV_SEQ_IOCTL_CREATE_PORT,
 151                                         port);
 152         if (err < 0)
 153                 goto error_port;
 154         announce_port = port->addr.port;
 155
 156         kfree(port);
 157         return 0;
 158
 159  error_port:
 160         snd_seq_system_client_done();
 161         kfree(port);
 162         return err;
 163 }
 164
 165
 166 /* unregister our internal client */
 167 void snd_seq_system_client_done(void)
 168 {
 169         int oldsysclient = sysclient;
 170
 171         if (oldsysclient >= 0) {
 172                 sysclient = -1;
 173                 announce_port = -1;
 174                 snd_seq_delete_kernel_client(oldsysclient);
 175         }
 176 }