ALSA: firewire-lib: Add support for MIDI capture/playback

For capturing/playbacking MIDI messages, this commit adds one MIDI conformant
data channel. This data channel has multiplexed 8 MIDI data streams. So this
data channel can transfer messages from/to 8 MIDI ports.

And this commit allows to set PCM format even if AMDTP streams already start.
I suppose the case that PCM substreams are going to be joined into AMDTP
streams when AMDTP streams are already started for MIDI substreams. Each
driver must count how many PCM/MIDI substreams use AMDTP streams to stop
AMDTP streams.

There are differences between specifications about MIDI conformant data.

About the multiplexing, IEC 61883-6:2002, itself, has no information. It
describes labels and bytes for MIDI messages and refers to MMA/AMEI RP-027
for 'successfull implementation'. MMA/AMEI RP-027 describes 8 MPX-MIDI data
streams for one MIDI conformant data channel. IEC 61883-6:2005 adds
'sequence multiplexing' and apply this way and describe incompatibility
between 2002 and 2005.

So this commit applies IEC 61883-6:2005. When we find some devices compliant
to IEC 61883-6:2002, then this difference should be handles as device quirk
in additional work.

About the number of bytes in an MIDI conformant data, IEC 61883-6:2002 describe
0,1,2,3 bytes. MMA/AMEI RP-027 describes 'MIDI1.0-1x-SPEED', 'MIDI1.0-2x-SPEED',
'MIDI1.0-3x-SPEED' modes and the maximum bytes for each mode corresponds to 1,
2, 3 bytes. The 'MIDI1.0-2x/3x-SPEED' modes are accompanied with 'negotiation
procedure' and 'encapsulation details' but there is no specifications for them.

So this commit implements 'MIDI1.0-1x-SPEED' mode for playback, but allows
to pick up 1-3 bytes for capturing.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp.c

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <sound/pcm.h>
+#include <sound/rawmidi.h>
 #include "amdtp.h"
 
 #define TICKS_PER_CYCLE		3072
@@ -123,9 +124,12 @@ void amdtp_stream_set_parameters(struct amdtp_stream *s,
 		[CIP_SFC_176400] = 176400,
 		[CIP_SFC_192000] = 192000,
 	};
-	unsigned int sfc;
+	unsigned int sfc, midi_channels;
 
-	if (WARN_ON(amdtp_stream_running(s)))
+	midi_channels = DIV_ROUND_UP(midi_ports, 8);
+
+	if (WARN_ON(amdtp_stream_running(s)) ||
+	    WARN_ON(midi_channels > AMDTP_MAX_CHANNELS_FOR_MIDI))
 		return;
 
 	for (sfc = 0; sfc < CIP_SFC_COUNT; ++sfc)
@@ -142,7 +146,7 @@ void amdtp_stream_set_parameters(struct amdtp_stream *s,
 		pcm_channels *= 2;
 	}
 	s->sfc = sfc;
-	s->data_block_quadlets = pcm_channels + DIV_ROUND_UP(midi_ports, 8);
+	s->data_block_quadlets = pcm_channels + midi_channels;
 	s->pcm_channels = pcm_channels;
 	s->midi_ports = midi_ports;
 
@@ -200,7 +204,7 @@ static void amdtp_read_s32_dualwire(struct amdtp_stream *s,
 void amdtp_stream_set_pcm_format(struct amdtp_stream *s,
 				 snd_pcm_format_t format)
 {
-	if (WARN_ON(amdtp_stream_running(s)))
+	if (WARN_ON(amdtp_stream_pcm_running(s)))
 		return;
 
 	switch (format) {
@@ -507,11 +511,41 @@ static void amdtp_fill_pcm_silence(struct amdtp_stream *s,
 static void amdtp_fill_midi(struct amdtp_stream *s,
 			    __be32 *buffer, unsigned int frames)
 {
-	unsigned int i;
+	unsigned int f, port;
+	u8 *b;
+
+	for (f = 0; f < frames; f++) {
+		buffer[s->pcm_channels + 1] = 0;
+		b = (u8 *)&buffer[s->pcm_channels + 1];
+
+		port = (s->data_block_counter + f) % 8;
+		if ((s->midi[port] == NULL) ||
+		    (snd_rawmidi_transmit(s->midi[port], b + 1, 1) <= 0))
+			b[0] = 0x80;
+		else
+			b[0] = 0x81;
+
+		buffer += s->data_block_quadlets;
+	}
+}
+
+static void amdtp_pull_midi(struct amdtp_stream *s,
+			    __be32 *buffer, unsigned int frames)
+{
+	unsigned int f, port;
+	int len;
+	u8 *b;
+
+	for (f = 0; f < frames; f++) {
+		port = (s->data_block_counter + f) % 8;
+		b = (u8 *)&buffer[s->pcm_channels + 1];
 
-	for (i = 0; i < frames; ++i)
-		buffer[s->pcm_channels + i * s->data_block_quadlets] =
-						cpu_to_be32(0x80000000);
+		len = b[0] - 0x80;
+		if ((1 <= len) &&  (len <= 3) && (s->midi[port]))
+			snd_rawmidi_receive(s->midi[port], b + 1, len);
+
+		buffer += s->data_block_quadlets;
+	}
 }
 
 static void update_pcm_pointers(struct amdtp_stream *s,
@@ -688,6 +722,9 @@ static void handle_in_packet(struct amdtp_stream *s,
 		pcm = ACCESS_ONCE(s->pcm);
 		if (pcm)
 			s->transfer_samples(s, pcm, buffer, data_blocks);
+
+		if (s->midi_ports)
+			amdtp_pull_midi(s, buffer, data_blocks);
 	}
 
 	s->data_block_counter = (data_block_counter + data_blocks) & 0xff;

sound/firewire/amdtp.h

@@ -46,9 +46,21 @@ enum cip_sfc {
 #define AMDTP_OUT_PCM_FORMAT_BITS	(SNDRV_PCM_FMTBIT_S16 | \
 					 SNDRV_PCM_FMTBIT_S32)
 
+
+/*
+ * AMDTP packet can include channels for MIDI conformant data.
+ * Each MIDI conformant data channel includes 8 MPX-MIDI data stream.
+ * Each MPX-MIDI data stream includes one data stream from/to MIDI ports.
+ *
+ * This module supports maximum 1 MIDI conformant data channels.
+ * Then this AMDTP packets can transfer maximum 8 MIDI data streams.
+ */
+#define AMDTP_MAX_CHANNELS_FOR_MIDI	1
+
 struct fw_unit;
 struct fw_iso_context;
 struct snd_pcm_substream;
+struct snd_rawmidi_substream;
 
 enum amdtp_stream_direction {
 	AMDTP_OUT_STREAM = 0,
@@ -90,6 +102,8 @@ struct amdtp_stream {
 	unsigned int pcm_buffer_pointer;
 	unsigned int pcm_period_pointer;
 	bool pointer_flush;
+
+	struct snd_rawmidi_substream *midi[AMDTP_MAX_CHANNELS_FOR_MIDI * 8];
 };
 
 int amdtp_stream_init(struct amdtp_stream *s, struct fw_unit *unit,
@@ -138,6 +152,17 @@ static inline bool amdtp_streaming_error(struct amdtp_stream *s)
 	return s->packet_index < 0;
 }
 
+/**
+ * amdtp_stream_pcm_running - check PCM substream is running or not
+ * @s: the AMDTP stream
+ *
+ * If this function returns true, PCM substream in the AMDTP stream is running.
+ */
+static inline bool amdtp_stream_pcm_running(struct amdtp_stream *s)
+{
+	return !!s->pcm;
+}
+
 /**
  * amdtp_stream_pcm_trigger - start/stop playback from a PCM device
  * @s: the AMDTP stream
@@ -153,6 +178,24 @@ static inline void amdtp_stream_pcm_trigger(struct amdtp_stream *s,
 	ACCESS_ONCE(s->pcm) = pcm;
 }
 
+/**
+ * amdtp_stream_midi_trigger - start/stop playback/capture with a MIDI device
+ * @s: the AMDTP stream
+ * @port: index of MIDI port
+ * @midi: the MIDI device to be started, or %NULL to stop the current device
+ *
+ * Call this function on a running isochronous stream to enable the actual
+ * transmission of MIDI data.  This function should be called from the MIDI
+ * device's .trigger callback.
+ */
+static inline void amdtp_stream_midi_trigger(struct amdtp_stream *s,
+					     unsigned int port,
+					     struct snd_rawmidi_substream *midi)
+{
+	if (port < s->midi_ports)
+		ACCESS_ONCE(s->midi[port]) = midi;
+}
+
 static inline bool cip_sfc_is_base_44100(enum cip_sfc sfc)
 {
 	return sfc & 1;