ALSA: pcm: Build pcm notifier code conditionally

The PCM notifier code is used only by OSS emulation layer, so we can
build it conditionally for reducing the size.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm.h

@@ -531,13 +531,6 @@ struct snd_pcm {
 #endif
 };
 
-struct snd_pcm_notify {
-	int (*n_register) (struct snd_pcm * pcm);
-	int (*n_disconnect) (struct snd_pcm * pcm);
-	int (*n_unregister) (struct snd_pcm * pcm);
-	struct list_head list;
-};
-
 /*
  *  Registering
  */
@@ -552,7 +545,15 @@ int snd_pcm_new_internal(struct snd_card *card, const char *id, int device,
 		struct snd_pcm **rpcm);
 int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count);
 
+#if IS_ENABLED(CONFIG_SND_PCM_OSS)
+struct snd_pcm_notify {
+	int (*n_register) (struct snd_pcm * pcm);
+	int (*n_disconnect) (struct snd_pcm * pcm);
+	int (*n_unregister) (struct snd_pcm * pcm);
+	struct list_head list;
+};
 int snd_pcm_notify(struct snd_pcm_notify *notify, int nfree);
+#endif
 
 /*
  *  Native I/O

sound/core/pcm.c

@@ -36,8 +36,10 @@ MODULE_DESCRIPTION("Midlevel PCM code for ALSA.");
 MODULE_LICENSE("GPL");
 
 static LIST_HEAD(snd_pcm_devices);
-static LIST_HEAD(snd_pcm_notify_list);
 static DEFINE_MUTEX(register_mutex);
+#if IS_ENABLED(CONFIG_SND_PCM_OSS)
+static LIST_HEAD(snd_pcm_notify_list);
+#endif
 
 static int snd_pcm_free(struct snd_pcm *pcm);
 static int snd_pcm_dev_free(struct snd_device *device);
@@ -884,16 +886,23 @@ static void snd_pcm_free_stream(struct snd_pcm_str * pstr)
 		put_device(&pstr->dev);
 }
 
+#if IS_ENABLED(CONFIG_SND_PCM_OSS)
+#define pcm_call_notify(pcm, call)					\
+	do {								\
+		struct snd_pcm_notify *_notify;				\
+		list_for_each_entry(_notify, &snd_pcm_notify_list, list) \
+			_notify->call(pcm);				\
+	} while (0)
+#else
+#define pcm_call_notify(pcm, call) /* NOP */
+#endif
+
 static int snd_pcm_free(struct snd_pcm *pcm)
 {
-	struct snd_pcm_notify *notify;
-
 	if (!pcm)
 		return 0;
-	if (!pcm->internal) {
-		list_for_each_entry(notify, &snd_pcm_notify_list, list)
-			notify->n_unregister(pcm);
-	}
+	if (!pcm->internal)
+		pcm_call_notify(pcm, n_unregister);
 	if (pcm->private_free)
 		pcm->private_free(pcm);
 	snd_pcm_lib_preallocate_free_for_all(pcm);
@@ -1069,7 +1078,6 @@ static int snd_pcm_dev_register(struct snd_device *device)
 {
 	int cidx, err;
 	struct snd_pcm_substream *substream;
-	struct snd_pcm_notify *notify;
 	struct snd_pcm *pcm;
 
 	if (snd_BUG_ON(!device || !device->device_data))
@@ -1107,8 +1115,7 @@ static int snd_pcm_dev_register(struct snd_device *device)
 			snd_pcm_timer_init(substream);
 	}
 
-	list_for_each_entry(notify, &snd_pcm_notify_list, list)
-		notify->n_register(pcm);
+	pcm_call_notify(pcm, n_register);
 
  unlock:
 	mutex_unlock(&register_mutex);
@@ -1118,7 +1125,6 @@ static int snd_pcm_dev_register(struct snd_device *device)
 static int snd_pcm_dev_disconnect(struct snd_device *device)
 {
 	struct snd_pcm *pcm = device->device_data;
-	struct snd_pcm_notify *notify;
 	struct snd_pcm_substream *substream;
 	int cidx;
 
@@ -1138,8 +1144,7 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 		}
 	}
 	if (!pcm->internal) {
-		list_for_each_entry(notify, &snd_pcm_notify_list, list)
-			notify->n_disconnect(pcm);
+		pcm_call_notify(pcm, n_disconnect);
 	}
 	for (cidx = 0; cidx < 2; cidx++) {
 		if (!pcm->internal)
@@ -1151,6 +1156,7 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_SND_PCM_OSS)
 /**
  * snd_pcm_notify - Add/remove the notify list
  * @notify: PCM notify list
@@ -1183,6 +1189,7 @@ int snd_pcm_notify(struct snd_pcm_notify *notify, int nfree)
 	return 0;
 }
 EXPORT_SYMBOL(snd_pcm_notify);
+#endif /* CONFIG_SND_PCM_OSS */
 
 #ifdef CONFIG_SND_PROC_FS
 /*