ALSA: ump: Don't create unused substreams for static blocks

When the UMP Endpoint is declared as "static", that is, no dynamic
reassignment of UMP Groups, it makes little sense to expose always all
16 groups with 16 substreams.  Many of those substreams are disabled
groups, hence they are useless, but applications don't know it and try
to open / access all those substreams unnecessarily.

This patch limits the number of UMP legacy rawmidi substreams only to
the active groups.  The behavior is changed only for the static
endpoint (i.e. devices without UMP v1.1 feature implemented or with
the static block flag is set).

Fixes: 0b5288f5 ("ALSA: ump: Add legacy raw MIDI support")
Link: https://lore.kernel.org/r/20230824075108.29958-4-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/ump.h

@@ -45,6 +45,7 @@ struct snd_ump_endpoint {
 	spinlock_t legacy_locks[2];
 	struct snd_rawmidi *legacy_rmidi;
 	struct snd_rawmidi_substream *legacy_substreams[2][SNDRV_UMP_MAX_GROUPS];
+	unsigned char legacy_mapping[SNDRV_UMP_MAX_GROUPS];
 
 	/* for legacy output; need to open the actual substream unlike input */
 	int legacy_out_opens;

sound/core/ump.c

@@ -984,7 +984,7 @@ static int snd_ump_legacy_open(struct snd_rawmidi_substream *substream)
 {
 	struct snd_ump_endpoint *ump = substream->rmidi->private_data;
 	int dir = substream->stream;
-	int group = substream->number;
+	int group = ump->legacy_mapping[substream->number];
 	int err;
 
 	mutex_lock(&ump->open_mutex);
@@ -1016,7 +1016,7 @@ static int snd_ump_legacy_close(struct snd_rawmidi_substream *substream)
 {
 	struct snd_ump_endpoint *ump = substream->rmidi->private_data;
 	int dir = substream->stream;
-	int group = substream->number;
+	int group = ump->legacy_mapping[substream->number];
 
 	mutex_lock(&ump->open_mutex);
 	spin_lock_irq(&ump->legacy_locks[dir]);
@@ -1123,6 +1123,34 @@ static void process_legacy_input(struct snd_ump_endpoint *ump, const u32 *src,
 	spin_unlock_irqrestore(&ump->legacy_locks[dir], flags);
 }
 
+/* Fill ump->legacy_mapping[] for groups to be used for legacy rawmidi */
+static int fill_legacy_mapping(struct snd_ump_endpoint *ump)
+{
+	struct snd_ump_block *fb;
+	unsigned int group_maps = 0;
+	int i, num;
+
+	if (ump->info.flags & SNDRV_UMP_EP_INFO_STATIC_BLOCKS) {
+		list_for_each_entry(fb, &ump->block_list, list) {
+			for (i = 0; i < fb->info.num_groups; i++)
+				group_maps |= 1U << (fb->info.first_group + i);
+		}
+		if (!group_maps)
+			ump_info(ump, "No UMP Group is found in FB\n");
+	}
+
+	/* use all groups for non-static case */
+	if (!group_maps)
+		group_maps = (1U << SNDRV_UMP_MAX_GROUPS) - 1;
+
+	num = 0;
+	for (i = 0; i < SNDRV_UMP_MAX_GROUPS; i++)
+		if (group_maps & (1U << i))
+			ump->legacy_mapping[num++] = i;
+
+	return num;
+}
+
 static void fill_substream_names(struct snd_ump_endpoint *ump,
 				 struct snd_rawmidi *rmidi, int dir)
 {
@@ -1130,7 +1158,7 @@ static void fill_substream_names(struct snd_ump_endpoint *ump,
 
 	list_for_each_entry(s, &rmidi->streams[dir].substreams, list)
 		snprintf(s->name, sizeof(s->name), "Group %d (%s)",
-			 s->number + 1, ump->info.name);
+			 ump->legacy_mapping[s->number] + 1, ump->info.name);
 }
 
 int snd_ump_attach_legacy_rawmidi(struct snd_ump_endpoint *ump,
@@ -1138,16 +1166,19 @@ int snd_ump_attach_legacy_rawmidi(struct snd_ump_endpoint *ump,
 {
 	struct snd_rawmidi *rmidi;
 	bool input, output;
-	int err;
+	int err, num;
 
-	ump->out_cvts = kcalloc(16, sizeof(*ump->out_cvts), GFP_KERNEL);
+	ump->out_cvts = kcalloc(SNDRV_UMP_MAX_GROUPS,
+				sizeof(*ump->out_cvts), GFP_KERNEL);
 	if (!ump->out_cvts)
 		return -ENOMEM;
 
+	num = fill_legacy_mapping(ump);
+
 	input = ump->core.info_flags & SNDRV_RAWMIDI_INFO_INPUT;
 	output = ump->core.info_flags & SNDRV_RAWMIDI_INFO_OUTPUT;
 	err = snd_rawmidi_new(ump->core.card, id, device,
-			      output ? 16 : 0, input ? 16 : 0,
+			      output ? num : 0, input ? num : 0,
 			      &rmidi);
 	if (err < 0) {
 		kfree(ump->out_cvts);