ALSA: seq: Add UMP support

Starting from this commit, we add the basic support of UMP (Universal
MIDI Packet) events on ALSA sequencer infrastructure.  The biggest
change here is that, for transferring UMP packets that are up to 128
bits, we extend the data payload of ALSA sequencer event record when
the client is declared to support for the new UMP events.

A new event flag bit, SNDRV_SEQ_EVENT_UMP, is defined and it shall be
set for the UMP packet events that have the larger payload of 128
bits, defined as struct snd_seq_ump_event.

For controlling the UMP feature enablement in kernel, a new Kconfig,
CONFIG_SND_SEQ_UMP is introduced.  The extended event for UMP is
available only when this Kconfig item is set.  Similarly, the size of
the internal snd_seq_event_cell also increases (in 4 bytes) when the
Kconfig item is set.  (But the size increase is effective only for
32bit architectures; 64bit archs already have padding there.)
Overall, when CONFIG_SND_SEQ_UMP isn't set, there is no change in the
event and cell, keeping the old sizes.

For applications that want to access the UMP packets, first of all, a
sequencer client has to declare the user-protocol to match with the
latest one via the new SNDRV_SEQ_IOCTL_USER_PVERSION; otherwise it's
treated as if a legacy client without UMP support.

Then the client can switch to the new UMP mode (MIDI 1.0 or MIDI 2.0)
with a new field, midi_version, in snd_seq_client_info.  When switched
to UMP mode (midi_version = 1 or 2), the client can write the UMP
events with SNDRV_SEQ_EVENT_UMP flag.  For reads, the alignment size
is changed from snd_seq_event (28 bytes) to snd_seq_ump_event (32
bytes).  When a UMP sequencer event is delivered to a legacy sequencer
client, it's ignored or handled as an error.

Conceptually, ALSA sequencer client and port correspond to the UMP
Endpoint and Group, respectively; each client may have multiple ports
and each port has the fixed number (16) of channels, total up to 256
channels.

As of this commit, ALSA sequencer core just sends and receives the UMP
events as-is from/to clients.  The automatic conversions between the
legacy events and the new UMP events will be implemented in a later
patch.

Along with this commit, bump the sequencer protocol version to 1.0.3.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-26-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 12 insertions, 0 deletions

diff --git a/include/sound/asequencer.h b/include/sound/asequencer.h
index 18d4bc3ee0b7..ddbb6bf801bb 100644
--- a/include/sound/asequencer.h
+++ b/include/sound/asequencer.h
@@ -65,6 +65,10 @@
 #define snd_seq_ev_is_abstime(ev)	(snd_seq_ev_timemode_type(ev) == SNDRV_SEQ_TIME_MODE_ABS)
 #define snd_seq_ev_is_reltime(ev)	(snd_seq_ev_timemode_type(ev) == SNDRV_SEQ_TIME_MODE_REL)
 
+/* check whether the given event is a UMP event */
+#define snd_seq_ev_is_ump(ev) \
+	(IS_ENABLED(CONFIG_SND_SEQ_UMP) && ((ev)->flags & SNDRV_SEQ_EVENT_UMP))
+
 /* queue sync port */
 #define snd_seq_queue_sync_port(q)	((q) + 16)
 
diff --git a/include/sound/seq_kernel.h b/include/sound/seq_kernel.h
index 527e7f8ad661..c8621671fa70 100644
--- a/include/sound/seq_kernel.h
+++ b/include/sound/seq_kernel.h
@@ -75,6 +75,14 @@ int snd_seq_expand_var_event_at(const struct snd_seq_event *event, int count,
 int snd_seq_dump_var_event(const struct snd_seq_event *event,
 			   snd_seq_dump_func_t func, void *private_data);
 
+/* size of the event packet; it can be greater than snd_seq_event size */
+static inline size_t snd_seq_event_packet_size(struct snd_seq_event *ev)
+{
+	if (snd_seq_ev_is_ump(ev))
+		return sizeof(struct snd_seq_ump_event);
+	return sizeof(struct snd_seq_event);
+}
+
 /* interface for OSS emulation */
 int snd_seq_set_queue_tempo(int client, struct snd_seq_queue_tempo *tempo);