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ALSA: seq: Skip notifications unless subscribed to announce port

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The notification via system announce port isn't a lightweight task,
hence it'd be better to skip if there is no subscription is done for
the announce port.  Implement a simple counter for checking that by
hooking the subscribe and unsubscribe callbacks.

Link: https://patch.msgid.link/20241128074801.32253-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2024-11-28 08:48:00 +01:00
parent b8e49e24cd
commit ec42af4a1f
1 changed files with 23 additions and 2 deletions
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25
sound/core/seq/seq_system.c
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@ -49,12 +49,14 @@ static int sysclient = -1;
/* port id numbers for this client */
static int announce_port = -1;
/* number of subscriptions to announce port */
static int announce_subscribed;
/* fill standard header data, source port & channel are filled in */
static int setheader(struct snd_seq_event * ev, int client, int port)
{
if (announce_port < 0)
if (announce_port < 0 || !announce_subscribed)
return -ENODEV;
memset(ev, 0, sizeof(struct snd_seq_event));
@ -104,6 +106,22 @@ static int event_input_timer(struct snd_seq_event * ev, int direct, void *privat
return snd_seq_control_queue(ev, atomic, hop);
}
static int sys_announce_subscribe(void *private_data,
struct snd_seq_port_subscribe *info)
{
announce_subscribed++;
return 0;
}
static int sys_announce_unsubscribe(void *private_data,
struct snd_seq_port_subscribe *info)
{
if (snd_BUG_ON(!announce_subscribed))
return 0;
announce_subscribed--;
return 0;
}
/* register our internal client */
int __init snd_seq_system_client_init(void)
{
@ -143,7 +161,10 @@ int __init snd_seq_system_client_init(void)
/* register announcement port */
strcpy(port->name, "Announce");
port->capability = SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ; /* for broadcast only */
port->kernel = NULL;
pcallbacks.event_input = NULL;
pcallbacks.subscribe = sys_announce_subscribe;
pcallbacks.unsubscribe = sys_announce_unsubscribe;
port->kernel = &pcallbacks;
port->type = 0;
port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
port->addr.client = sysclient;