From 7fbd1753b64eafe21cf842348a40a691d0dee440 Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Date: Mon, 1 Jul 2019 23:43:53 +0900
Subject: [PATCH 5/7] ALSA: firewire-lib/fireworks: fix miss detection of received MIDI messages
Git-commit: 7fbd1753b64eafe21cf842348a40a691d0dee440
Patch-mainline: v5.2
References: bsc#1051510
In IEC 61883-6, 8 MIDI data streams are multiplexed into single
MIDI conformant data channel. The index of stream is calculated by
modulo 8 of the value of data block counter.
In fireworks, the value of data block counter in CIP header has a quirk
with firmware version v5.0.0, v5.7.3 and v5.8.0. This brings ALSA
IEC 61883-1/6 packet streaming engine to miss detection of MIDI
messages.
This commit fixes the miss detection to modify the value of data block
counter for the modulo calculation.
For maintainers, this bug exists since a commit 18f5ed365d3f ("ALSA:
Fireworks/firewire-lib: add support for recent firmware quirk") in Linux
kernel v4.2. There're many changes since the commit. This fix can be
backported to Linux kernel v4.4 or later. I tagged a base commit to the
backport for your convenience.
Besides, my work for Linux kernel v5.3 brings heavy code refactoring and
some structure members are renamed in 'sound/firewire/amdtp-stream.h'.
The content of this patch brings conflict when merging -rc tree with
this patch and the latest tree. I request maintainers to solve the
conflict to replace 'tx_first_dbc' with 'ctx_data.tx.first_dbc'.
Fixes: df075feefbd3 ("ALSA: firewire-lib: complete AM824 data block processing layer")
Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/firewire/amdtp-am824.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/firewire/amdtp-am824.c b/sound/firewire/amdtp-am824.c
index 4210e5c6262e..d09da9dbf235 100644
--- a/sound/firewire/amdtp-am824.c
+++ b/sound/firewire/amdtp-am824.c
@@ -321,7 +321,7 @@ static void read_midi_messages(struct amdtp_stream *s,
u8 *b;
for (f = 0; f < frames; f++) {
- port = (s->data_block_counter + f) % 8;
+ port = (8 - s->tx_first_dbc + s->data_block_counter + f) % 8;
b = (u8 *)&buffer[p->midi_position];
len = b[0] - 0x80;
--
2.16.4