[alsa-devel] [PATCH] ALSA: firewire-lib/fireworks: fix miss detection of received MIDI messages

[Takashi Iwai]

On Fri, 28 Jun 2019 09:34:00 +0200,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> On Fri, Jun 28, 2019, at 17:53, Takashi Iwai wrote:
> > On Fri, 28 Jun 2019 07:21:58 +0200,
> > Takashi Sakamoto wrote:
> > > 
> > > 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.
> > > 
> > > Fixes: df075feefbd3 ("ALSA: firewire-lib: complete AM824 data block processing layer")
> > > Cc: <stable at vger.kernel.org> # v4.4+
> > > Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
> > 
> > This doesn't seem applicable to the latest 5.2-rc tree due to your
> > recent refactoring.  Could you resubmit the fix for 5.2?  I'll resolve
> > the merge conflict in my side.
> 
> Mmm. Do you actually encounter any conflict when applying this patch to
> your v5.2 tree?
> 
> This patch includes changes for `sound/firewire/amdtp-am824.c`. On the other
> hand, my recent work is mainly for `sound/firewire/amdtp-stream.c`. Actually,
> the last change for `amdtp-am824.c` was done 2017-10-25.
> https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/log/sound/firewire/amdtp-am824.c?h=for-linus

It's not about file conflicts but the compilation fails after the
patch.
sound/firewire/amdtp-am824.c: In function ‘read_midi_messages’:
sound/firewire/amdtp-am824.c:324:16: error: ‘struct amdtp_stream’ has no member named ‘ctx_data’
   port = (8 - s->ctx_data.tx.first_dbc + s->data_block_counter + f) % 8;
                ^~


thanks,

Takashi