ALSA: firewire-lib: add helper functions for asynchronous transactions to transfer MIDI messages

Some models receive MIDI messages via IEEE 1394 asynchronous transactions.
In this case, MIDI messages are transferred in fixed-length payload. It's
nice that firewire-lib module has common helper functions.

This commit implements this idea. Each driver adds
'struct snd_fw_async_midi_port' in its instance structure. In probing,
it should call snd_fw_async_midi_port_init() to initialize the
structure with some parameters such as target address, the length
of payload in a transaction and a pointer for callback function
to fill the payload buffer. At 'struct snd_rawmidi_ops.trigger()'
callback, it should call 'snd_fw_async_midi_port_run()' to start
transactions. Each driver should ensure that the lifetime of MIDI
substream continues till calling 'snd_fw_async_midi_port_finish()'.

The helper functions support retries to transferring MIDI messages when
transmission errors occur. When transactions are successful, the helper
functions call 'snd_rawmidi_transmit_ack()' internally to consume MIDI
bytes in the buffer. Therefore, Each driver is expected to use
'snd_rawmidi_transmit_peek()' to tell the number of bytes to transfer to
return value of 'fill' callback.

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

1 files changed, 50 insertions, 0 deletions

diff --git a/sound/firewire/lib.h b/sound/firewire/lib.h
index 02cfabc9c3c4..37a7fe4235f2 100644
--- a/sound/firewire/lib.h
+++ b/sound/firewire/lib.h
@@ -3,6 +3,8 @@
 
 #include <linux/firewire-constants.h>
 #include <linux/types.h>
+#include <linux/sched.h>
+#include <sound/rawmidi.h>
 
 struct fw_unit;
 
@@ -20,4 +22,52 @@ static inline bool rcode_is_permanent_error(int rcode)
 	return rcode == RCODE_TYPE_ERROR || rcode == RCODE_ADDRESS_ERROR;
 }
 
+struct snd_fw_async_midi_port;
+typedef int (*snd_fw_async_midi_port_fill)(
+				struct snd_rawmidi_substream *substream,
+				u8 *buf);
+
+struct snd_fw_async_midi_port {
+	struct fw_device *parent;
+	struct work_struct work;
+
+	u64 addr;
+	struct fw_transaction transaction;
+
+	u8 *buf;
+	unsigned int len;
+
+	struct snd_rawmidi_substream *substream;
+	snd_fw_async_midi_port_fill fill;
+	unsigned int consume_bytes;
+};
+
+int snd_fw_async_midi_port_init(struct snd_fw_async_midi_port *port,
+		struct fw_unit *unit, u64 addr, unsigned int len,
+		snd_fw_async_midi_port_fill fill);
+void snd_fw_async_midi_port_destroy(struct snd_fw_async_midi_port *port);
+
+/**
+ * snd_fw_async_midi_port_run - run transactions for the async MIDI port
+ * @port: the asynchronous MIDI port
+ * @substream: the MIDI substream
+ */
+static inline void
+snd_fw_async_midi_port_run(struct snd_fw_async_midi_port *port,
+			   struct snd_rawmidi_substream *substream)
+{
+	port->substream = substream;
+	schedule_work(&port->work);
+}
+
+/**
+ * snd_fw_async_midi_port_finish - finish the asynchronous MIDI port
+ * @port: the asynchronous MIDI port
+ */
+static inline void
+snd_fw_async_midi_port_finish(struct snd_fw_async_midi_port *port)
+{
+	port->substream = NULL;
+}
+
 #endif