From f17b62a01f6767176335f5668c756d24ada5b556 Mon Sep 17 00:00:00 2001 From: Takashi Sakamoto Date: Mon, 1 Jul 2019 23:43:53 +0900 Subject: [PATCH] ALSA: firewire-lib/fireworks: fix miss detection of received MIDI messages 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 5e8cf06c8c6d ("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: 37d52359e8a0 ("ALSA: firewire-lib: complete AM824 data block processing layer") Cc: # v4.4+ Signed-off-by: Takashi Sakamoto Signed-off-by: Takashi Iwai --- 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 4210e5c6262eb..d09da9dbf235f 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; -- 2.39.5