ALSA: firewire-lib: add a restriction for a transaction at once

Currently, when waiting for a response, callers can start another
transaction by scheduling another work. This is not good for error
processing of transaction, especially the first response is too late.

This commit serialize request/response transactions, by adding one
boolean member to represent idling state.

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

2 files changed, 10 insertions, 0 deletions

diff --git a/sound/firewire/lib.c b/sound/firewire/lib.c
index 03ada3f1047a..ddc3e88ee0d1 100644
--- a/sound/firewire/lib.c
+++ b/sound/firewire/lib.c
@@ -76,6 +76,8 @@ static void async_midi_port_callback(struct fw_card *card, int rcode,
 
         if (rcode == RCODE_COMPLETE && substream != NULL)
                 snd_rawmidi_transmit_ack(substream, port->consume_bytes);
+
+        port->idling = true;
 }
 
 static void midi_port_work(struct work_struct *work)
@@ -86,6 +88,10 @@ static void midi_port_work(struct work_struct *work)
         int generation;
         int type;
 
+        /* Under transacting. */
+        if (!port->idling)
+                return;
+
         /* Nothing to do. */
         if (substream == NULL || snd_rawmidi_transmit_empty(substream))
                 return;
@@ -110,6 +116,8 @@ static void midi_port_work(struct work_struct *work)
                 type = TCODE_WRITE_BLOCK_REQUEST;
 
         /* Start this transaction. */
+        port->idling = false;
+
         /*
          * In Linux FireWire core, when generation is updated with memory
          * barrier, node id has already been updated. In this module, After
@@ -150,6 +158,7 @@ int snd_fw_async_midi_port_init(struct snd_fw_async_midi_port *port,
         port->parent = fw_parent_device(unit);
         port->addr = addr;
         port->fill = fill;
+        port->idling = true;
 
         INIT_WORK(&port->work, midi_port_work);
 
diff --git a/sound/firewire/lib.h b/sound/firewire/lib.h
index 37a7fe4235f2..0af06f44e8c2 100644
--- a/sound/firewire/lib.h
+++ b/sound/firewire/lib.h
@@ -30,6 +30,7 @@ typedef int (*snd_fw_async_midi_port_fill)(
 struct snd_fw_async_midi_port {
         struct fw_device *parent;
         struct work_struct work;
+        bool idling;
 
         u64 addr;
         struct fw_transaction transaction;