linux-kernel - [PATCH 5.13 004/800] ALSA: bebob: fix rx packet format for Yamaha GO44/GO46, Terratec Phase 24/x24

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Date:   Mon, 12 Jul 2021 08:00:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Takashi Sakamoto <o-takashi@...amocchi.jp>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 5.13 004/800] ALSA: bebob: fix rx packet format for Yamaha GO44/GO46, Terratec Phase 24/x24

From: Takashi Sakamoto <o-takashi@...amocchi.jp>

commit 6b6c17fe6fa58900fa69dd000d5333b679e5e33e upstream.

Below devices reports zero as the number of channels for external output
plug with MIDI type:

 * Yamaha GO44/GO46
 * Terratec Phase 24/X24

As a result, rx packet format is invalid and they generate silent sound.
This is a regression added in v5.13.

This commit fixes the bug, addressed at a commit 1bd1b3be8655 ("ALSA:
bebob: perform sequence replay for media clock recovery").

Cc: <stable@...r.kernel.org>
Fixes: 5c6ea94f2b7c ("ALSA: bebob: detect the number of available MIDI ports")
Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
Link: https://lore.kernel.org/r/20210618040447.113306-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/firewire/bebob/bebob_stream.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/sound/firewire/bebob/bebob_stream.c
+++ b/sound/firewire/bebob/bebob_stream.c
@@ -883,6 +883,11 @@ static int detect_midi_ports(struct snd_
 		err = avc_bridgeco_get_plug_ch_count(bebob->unit, addr, &ch_count);
 		if (err < 0)
 			break;
+		// Yamaha GO44, GO46, Terratec Phase 24, Phase x24 reports 0 for the number of
+		// channels in external output plug 3 (MIDI type) even if it has a pair of physical
+		// MIDI jacks. As a workaround, assume it as one.
+		if (ch_count == 0)
+			ch_count = 1;
 		*midi_ports += ch_count;
 	}
 
@@ -961,12 +966,12 @@ int snd_bebob_stream_discover(struct snd
 	if (err < 0)
 		goto end;
 
-	err = detect_midi_ports(bebob, bebob->rx_stream_formations, addr, AVC_BRIDGECO_PLUG_DIR_IN,
+	err = detect_midi_ports(bebob, bebob->tx_stream_formations, addr, AVC_BRIDGECO_PLUG_DIR_IN,
 				plugs[2], &bebob->midi_input_ports);
 	if (err < 0)
 		goto end;
 
-	err = detect_midi_ports(bebob, bebob->tx_stream_formations, addr, AVC_BRIDGECO_PLUG_DIR_OUT,
+	err = detect_midi_ports(bebob, bebob->rx_stream_formations, addr, AVC_BRIDGECO_PLUG_DIR_OUT,
 				plugs[3], &bebob->midi_output_ports);
 	if (err < 0)
 		goto end;