ALSA: firewire-lib: add a kernel API to start AMDTP streams in AMDTP domain

This commit adds a kernel API to start a couple of isochronous contexts
for some AMDTP streams.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp-stream.c

@@ -1185,6 +1185,30 @@ int amdtp_domain_add_stream(struct amdtp_domain *d, struct amdtp_stream *s,
 }
 EXPORT_SYMBOL_GPL(amdtp_domain_add_stream);
 
+/**
+ * amdtp_domain_start - start sending packets for isoc context in the domain.
+ * @d: the AMDTP domain.
+ */
+int amdtp_domain_start(struct amdtp_domain *d)
+{
+	struct amdtp_stream *s;
+	int err = 0;
+
+	list_for_each_entry(s, &d->streams, list) {
+		err = amdtp_stream_start(s, s->channel, s->speed);
+		if (err < 0)
+			break;
+	}
+
+	if (err < 0) {
+		list_for_each_entry(s, &d->streams, list)
+			amdtp_stream_stop(s);
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(amdtp_domain_start);
+
 /**
  * amdtp_domain_stop - stop sending packets for isoc context in the same domain.
  * @d: the AMDTP domain to which the isoc contexts belong.

sound/firewire/amdtp-stream.h

@@ -282,6 +282,7 @@ void amdtp_domain_destroy(struct amdtp_domain *d);
 int amdtp_domain_add_stream(struct amdtp_domain *d, struct amdtp_stream *s,
 			    int channel, int speed);
 
+int amdtp_domain_start(struct amdtp_domain *d);
 void amdtp_domain_stop(struct amdtp_domain *d);
 
 #endif