ALSA: seq: Add UMP group filter

Add a new filter bitmap for UMP groups for reducing the unnecessary
read/write when the client is connected to UMP EP seq port.

The new group_filter field contains the bitmap for the groups, i.e.
when the bit is set, the corresponding group is filtered out and
the messages to that group won't be delivered.

The filter bitmap consists of each bit of 1-based UMP Group number.
The bit 0 is reserved for the future use.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-37-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: tiwai

include/uapi/sound/asequencer.h

@@ -362,7 +362,8 @@ struct snd_seq_client_info {
 	int card;			/* RO: card number[kernel] */
 	int pid;			/* RO: pid[user] */
 	unsigned int midi_version;	/* MIDI version */
-	char reserved[52];		/* for future use */
+	unsigned int group_filter;	/* UMP group filter bitmap (for 1-based Group indices) */
+	char reserved[48];		/* for future use */
 };
 
 /* MIDI version numbers in client info */

sound/core/seq/seq_clientmgr.c

@@ -1229,6 +1229,7 @@ static void get_client_info(struct snd_seq_client *cptr,
 	info->filter = cptr->filter;
 	info->event_lost = cptr->event_lost;
 	memcpy(info->event_filter, cptr->event_filter, 32);
+	info->group_filter = cptr->group_filter;
 	info->num_ports = cptr->num_ports;
 
 	if (cptr->type == USER_CLIENT)
@@ -1290,6 +1291,7 @@ static int snd_seq_ioctl_set_client_info(struct snd_seq_client *client,
 	if (client->user_pversion >= SNDRV_PROTOCOL_VERSION(1, 0, 3))
 		client->midi_version = client_info->midi_version;
 	memcpy(client->event_filter, client_info->event_filter, 32);
+	client->group_filter = client_info->group_filter;
 	return 0;
 }
 

sound/core/seq/seq_clientmgr.h

@@ -40,6 +40,7 @@ struct snd_seq_client {
 	int number;		/* client number */
 	unsigned int filter;	/* filter flags */
 	DECLARE_BITMAP(event_filter, 256);
+	unsigned short group_filter;
 	snd_use_lock_t use_lock;
 	int event_lost;
 	/* ports */

sound/core/seq/seq_ump_convert.c

@@ -527,6 +527,17 @@ static int deliver_with_group_convert(struct snd_seq_client *dest,
 					      atomic, hop);
 }
 
+/* apply the UMP event filter; return true to skip the event */
+static bool ump_event_filtered(struct snd_seq_client *dest,
+			       const struct snd_seq_ump_event *ev)
+{
+	unsigned char group;
+
+	group = ump_message_group(ev->ump[0]);
+	/* check the bitmap for 1-based group number */
+	return dest->group_filter & (1U << (group + 1));
+}
+
 /* Convert from UMP packet and deliver */
 int snd_seq_deliver_from_ump(struct snd_seq_client *source,
 			     struct snd_seq_client *dest,
@@ -539,6 +550,8 @@ int snd_seq_deliver_from_ump(struct snd_seq_client *source,
 
 	if (snd_seq_ev_is_variable(event))
 		return 0; // skip, no variable event for UMP, so far
+	if (ump_event_filtered(dest, ump_ev))
+		return 0; // skip if group filter is set and matching
 	type = ump_message_type(ump_ev->ump[0]);
 
 	if (snd_seq_client_is_ump(dest)) {