ALSA: seq: Add port direction to snd_seq_port_info

Add a new field "direction" to snd_seq_port_info for allowing a client
to tell the expected direction of the port access.  A port might still
allow subscriptions for read/write (e.g. for MIDI-CI) even if the
primary usage of the port is a single direction (either input or
output only).  This new "direction" field can help to indicate such
cases.

When the direction is unspecified at creating a port and the port has
either read or write capability, the corresponding direction bits are
set automatically as default.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-29-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/asequencer.h

@@ -455,6 +455,12 @@ struct snd_seq_remove_events {
 #define SNDRV_SEQ_PORT_FLG_TIMESTAMP	(1<<1)
 #define SNDRV_SEQ_PORT_FLG_TIME_REAL	(1<<2)
 
+/* port direction */
+#define SNDRV_SEQ_PORT_DIR_UNKNOWN	0
+#define SNDRV_SEQ_PORT_DIR_INPUT	1
+#define SNDRV_SEQ_PORT_DIR_OUTPUT	2
+#define SNDRV_SEQ_PORT_DIR_BIDIRECTION	3
+
 struct snd_seq_port_info {
 	struct snd_seq_addr addr;	/* client/port numbers */
 	char name[64];			/* port name */
@@ -471,7 +477,8 @@ struct snd_seq_port_info {
 	void *kernel;			/* reserved for kernel use (must be NULL) */
 	unsigned int flags;		/* misc. conditioning */
 	unsigned char time_queue;	/* queue # for timestamping */
-	char reserved[59];		/* for future use */
+	unsigned char direction;	/* port usage direction (r/w/bidir) */
+	char reserved[58];		/* for future use */
 };
 
 

sound/core/seq/seq_clientmgr.c

@@ -2440,6 +2440,17 @@ static void snd_seq_info_dump_subscribers(struct snd_info_buffer *buffer,
 
 #define FLAG_PERM_DUPLEX(perm) ((perm) & SNDRV_SEQ_PORT_CAP_DUPLEX ? 'X' : '-')
 
+static const char *port_direction_name(unsigned char dir)
+{
+	static const char *names[4] = {
+		"-", "In", "Out", "In/Out"
+	};
+
+	if (dir > SNDRV_SEQ_PORT_DIR_BIDIRECTION)
+		return "Invalid";
+	return names[dir];
+}
+
 static void snd_seq_info_dump_ports(struct snd_info_buffer *buffer,
 				    struct snd_seq_client *client)
 {
@@ -2449,12 +2460,13 @@ static void snd_seq_info_dump_ports(struct snd_info_buffer *buffer,
 	list_for_each_entry(p, &client->ports_list_head, list) {
 		if (p->capability & SNDRV_SEQ_PORT_CAP_INACTIVE)
 			continue;
-		snd_iprintf(buffer, "  Port %3d : \"%s\" (%c%c%c%c)\n",
+		snd_iprintf(buffer, "  Port %3d : \"%s\" (%c%c%c%c) [%s]\n",
 			    p->addr.port, p->name,
 			    FLAG_PERM_RD(p->capability),
 			    FLAG_PERM_WR(p->capability),
 			    FLAG_PERM_EX(p->capability),
-			    FLAG_PERM_DUPLEX(p->capability));
+			    FLAG_PERM_DUPLEX(p->capability),
+			    port_direction_name(p->direction));
 		snd_seq_info_dump_subscribers(buffer, &p->c_src, 1, "    Connecting To: ");
 		snd_seq_info_dump_subscribers(buffer, &p->c_dest, 0, "    Connected From: ");
 	}

sound/core/seq/seq_dummy.c

@@ -127,6 +127,7 @@ create_port(int idx, int type)
 	pinfo.capability |= SNDRV_SEQ_PORT_CAP_WRITE | SNDRV_SEQ_PORT_CAP_SUBS_WRITE;
 	if (duplex)
 		pinfo.capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
+	pinfo.direction = SNDRV_SEQ_PORT_DIR_BIDIRECTION;
 	pinfo.type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
 		| SNDRV_SEQ_PORT_TYPE_SOFTWARE
 		| SNDRV_SEQ_PORT_TYPE_PORT;

sound/core/seq/seq_midi.c

@@ -367,6 +367,10 @@ snd_seq_midisynth_probe(struct device *_dev)
 		if ((port->capability & (SNDRV_SEQ_PORT_CAP_WRITE|SNDRV_SEQ_PORT_CAP_READ)) == (SNDRV_SEQ_PORT_CAP_WRITE|SNDRV_SEQ_PORT_CAP_READ) &&
 		    info->flags & SNDRV_RAWMIDI_INFO_DUPLEX)
 			port->capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
+		if (port->capability & SNDRV_SEQ_PORT_CAP_READ)
+			port->direction |= SNDRV_SEQ_PORT_DIR_INPUT;
+		if (port->capability & SNDRV_SEQ_PORT_CAP_WRITE)
+			port->direction |= SNDRV_SEQ_PORT_DIR_OUTPUT;
 		port->type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
 			| SNDRV_SEQ_PORT_TYPE_HARDWARE
 			| SNDRV_SEQ_PORT_TYPE_PORT;

sound/core/seq/seq_ports.c

@@ -356,6 +356,16 @@ int snd_seq_set_port_info(struct snd_seq_client_port * port,
 	port->time_real = (info->flags & SNDRV_SEQ_PORT_FLG_TIME_REAL) ? 1 : 0;
 	port->time_queue = info->time_queue;
 
+	/* direction */
+	port->direction = info->direction;
+	/* fill default port direction */
+	if (!port->direction) {
+		if (info->capability & SNDRV_SEQ_PORT_CAP_READ)
+			port->direction |= SNDRV_SEQ_PORT_DIR_INPUT;
+		if (info->capability & SNDRV_SEQ_PORT_CAP_WRITE)
+			port->direction |= SNDRV_SEQ_PORT_DIR_OUTPUT;
+	}
+
 	return 0;
 }
 
@@ -393,6 +403,9 @@ int snd_seq_get_port_info(struct snd_seq_client_port * port,
 		info->time_queue = port->time_queue;
 	}
 
+	/* direction */
+	info->direction = port->direction;
+
 	return 0;
 }
 

sound/core/seq/seq_ports.h

@@ -72,6 +72,8 @@ struct snd_seq_client_port {
 	int midi_voices;
 	int synth_voices;
 		
+	/* direction */
+	unsigned char direction;
 };
 
 struct snd_seq_client;

sound/core/seq/seq_virmidi.c

@@ -385,6 +385,7 @@ static int snd_virmidi_dev_attach_seq(struct snd_virmidi_dev *rdev)
 	pinfo->capability |= SNDRV_SEQ_PORT_CAP_WRITE | SNDRV_SEQ_PORT_CAP_SYNC_WRITE | SNDRV_SEQ_PORT_CAP_SUBS_WRITE;
 	pinfo->capability |= SNDRV_SEQ_PORT_CAP_READ | SNDRV_SEQ_PORT_CAP_SYNC_READ | SNDRV_SEQ_PORT_CAP_SUBS_READ;
 	pinfo->capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
+	pinfo->direction = SNDRV_SEQ_PORT_DIR_BIDIRECTION;
 	pinfo->type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
 		| SNDRV_SEQ_PORT_TYPE_SOFTWARE
 		| SNDRV_SEQ_PORT_TYPE_PORT;