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>
This commit is contained in:
Takashi Sakamoto 2015-10-09 08:10:25 +09:00 committed by Takashi Iwai
parent 694470273d
commit 585d7cba5e
2 changed files with 153 additions and 0 deletions

View file

@ -9,6 +9,7 @@
#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/module.h>
#include <linux/slab.h>
#include "lib.h"
#define ERROR_RETRY_DELAY_MS 20
@ -66,6 +67,108 @@ int snd_fw_transaction(struct fw_unit *unit, int tcode,
}
EXPORT_SYMBOL(snd_fw_transaction);
static void async_midi_port_callback(struct fw_card *card, int rcode,
void *data, size_t length,
void *callback_data)
{
struct snd_fw_async_midi_port *port = callback_data;
struct snd_rawmidi_substream *substream = ACCESS_ONCE(port->substream);
if (rcode == RCODE_COMPLETE && substream != NULL)
snd_rawmidi_transmit_ack(substream, port->consume_bytes);
}
static void midi_port_work(struct work_struct *work)
{
struct snd_fw_async_midi_port *port =
container_of(work, struct snd_fw_async_midi_port, work);
struct snd_rawmidi_substream *substream = ACCESS_ONCE(port->substream);
int generation;
int type;
/* Nothing to do. */
if (substream == NULL || snd_rawmidi_transmit_empty(substream))
return;
/*
* Fill the buffer. The callee must use snd_rawmidi_transmit_peek().
* Later, snd_rawmidi_transmit_ack() is called.
*/
memset(port->buf, 0, port->len);
port->consume_bytes = port->fill(substream, port->buf);
if (port->consume_bytes <= 0) {
/* Do it in next chance, immediately. */
if (port->consume_bytes == 0)
schedule_work(&port->work);
return;
}
/* Calculate type of transaction. */
if (port->len == 4)
type = TCODE_WRITE_QUADLET_REQUEST;
else
type = TCODE_WRITE_BLOCK_REQUEST;
/* Start this transaction. */
/*
* In Linux FireWire core, when generation is updated with memory
* barrier, node id has already been updated. In this module, After
* this smp_rmb(), load/store instructions to memory are completed.
* Thus, both of generation and node id are available with recent
* values. This is a light-serialization solution to handle bus reset
* events on IEEE 1394 bus.
*/
generation = port->parent->generation;
smp_rmb();
fw_send_request(port->parent->card, &port->transaction, type,
port->parent->node_id, generation,
port->parent->max_speed, port->addr,
port->buf, port->len, async_midi_port_callback,
port);
}
/**
* snd_fw_async_midi_port_init - initialize asynchronous MIDI port structure
* @port: the asynchronous MIDI port to initialize
* @unit: the target of the asynchronous transaction
* @addr: the address to which transactions are transferred
* @len: the length of transaction
* @fill: the callback function to fill given buffer, and returns the
* number of consumed bytes for MIDI message.
*
*/
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)
{
port->len = DIV_ROUND_UP(len, 4) * 4;
port->buf = kzalloc(port->len, GFP_KERNEL);
if (port->buf == NULL)
return -ENOMEM;
port->parent = fw_parent_device(unit);
port->addr = addr;
port->fill = fill;
INIT_WORK(&port->work, midi_port_work);
return 0;
}
EXPORT_SYMBOL(snd_fw_async_midi_port_init);
/**
* snd_fw_async_midi_port_destroy - free asynchronous MIDI port structure
* @port: the asynchronous MIDI port structure
*/
void snd_fw_async_midi_port_destroy(struct snd_fw_async_midi_port *port)
{
snd_fw_async_midi_port_finish(port);
cancel_work_sync(&port->work);
kfree(port->buf);
}
EXPORT_SYMBOL(snd_fw_async_midi_port_destroy);
MODULE_DESCRIPTION("FireWire audio helper functions");
MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
MODULE_LICENSE("GPL v2");

View file

@ -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