ALSA: seq: Allow suppressing UMP conversions

A sequencer client like seq_dummy rather doesn't want to convert UMP
events but receives / sends as is.  Add a new event filter flag to
suppress the automatic UMP conversion and applies accordingly.
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-32-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/asequencer.h

@@ -347,6 +347,7 @@ typedef int __bitwise snd_seq_client_type_t;
 #define SNDRV_SEQ_FILTER_BROADCAST	(1U<<0)	/* accept broadcast messages */
 #define SNDRV_SEQ_FILTER_MULTICAST	(1U<<1)	/* accept multicast messages */
 #define SNDRV_SEQ_FILTER_BOUNCE		(1U<<2)	/* accept bounce event in error */
+#define SNDRV_SEQ_FILTER_NO_CONVERT	(1U<<30) /* don't convert UMP events */
 #define SNDRV_SEQ_FILTER_USE_EVENT	(1U<<31)	/* use event filter */
 
 struct snd_seq_client_info {

sound/core/seq/seq_clientmgr.c

@@ -671,6 +671,7 @@ static int snd_seq_deliver_single_event(struct snd_seq_client *client,
 					  dest_port->time_real);
 
 #if IS_ENABLED(CONFIG_SND_SEQ_UMP)
+	if (!(dest->filter & SNDRV_SEQ_FILTER_NO_CONVERT)) {
 		if (snd_seq_ev_is_ump(event)) {
 			result = snd_seq_deliver_from_ump(client, dest, dest_port,
 							  event, atomic, hop);
@@ -680,6 +681,7 @@ static int snd_seq_deliver_single_event(struct snd_seq_client *client,
 							event, atomic, hop);
 			goto __skip;
 		}
+	}
 #endif /* CONFIG_SND_SEQ_UMP */
 
 	result = __snd_seq_deliver_single_event(dest, dest_port, event,

sound/core/seq/seq_dummy.c

@@ -152,6 +152,7 @@ static int __init
 register_client(void)
 {
 	struct snd_seq_dummy_port *rec1, *rec2;
+	struct snd_seq_client *client;
 	int i;
 
 	if (ports < 1) {
@@ -165,6 +166,13 @@ register_client(void)
 	if (my_client < 0)
 		return my_client;
 
+	/* don't convert events but just pass-through */
+	client = snd_seq_kernel_client_get(my_client);
+	if (!client)
+		return -EINVAL;
+	client->filter = SNDRV_SEQ_FILTER_NO_CONVERT;
+	snd_seq_kernel_client_put(client);
+
 	/* create ports */
 	for (i = 0; i < ports; i++) {
 		rec1 = create_port(i, 0);