In data blocks of common isochronous packet for MOTU devices, PCM frames are multiplexed in a shape of '24 bit * 4 Audio Pack', described in IEC 61883-6. The frames are not aligned to quadlet.

For capture PCM substream, ALSA firewire-motu driver constructs PCM frames by reading data blocks byte-by-byte. However this operation includes bug for lower byte of the PCM sample. This brings invalid content of the PCM samples.

This commit fixes the bug.

Reported-by: Peter Sjöberg autopeter@gmail.com Cc: stable@vger.kernel.org # v4.12+ Fixes: 4641c9394010 ("ALSA: firewire-motu: add MOTU specific protocol layer") Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- sound/firewire/motu/amdtp-motu.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/firewire/motu/amdtp-motu.c b/sound/firewire/motu/amdtp-motu.c index f0555a24d90e..6c9b743ea74b 100644 --- a/sound/firewire/motu/amdtp-motu.c +++ b/sound/firewire/motu/amdtp-motu.c @@ -136,7 +136,9 @@ static void read_pcm_s32(struct amdtp_stream *s, byte = (u8 *)buffer + p->pcm_byte_offset;

for (c = 0; c < channels; ++c) { - *dst = (byte[0] << 24) | (byte[1] << 16) | byte[2]; + *dst = (byte[0] << 24) | + (byte[1] << 16) | + (byte[2] << 8); byte += 3; dst++; }