Re: something went wrong with USB iJack data in kernel 6.x

[Takashi Iwai <tiwai@xxxxxxx>]

On Mon, 14 Oct 2024 18:03:40 +0200,
Paul Davis wrote:
> 
> The thing that puzzles me is that the iJack strings are missing from
> the output of libusb -v, which AFAIU is 100% independent of any ALSA
> code whatsoever. This makes me suspect that no ALSA code is involved
> in this regression. I've also determined since my email that some
> other devices (e.g. an Ableton Push 2) do have iJack name data with
> the 6.x kernel.
> 
> However, things got curiouser as I was trying to get the output of
> alsa-info. It seems that under some conditions, the iJack strings for
> the problematic device are available/displayed with lsusb. My initial
> run of alsa-info showed the iJack strings, subsequent runs of
> alsa-info and/or lsusb -v do not. I also see a continuous stream of
> USB device resets (though these are not happening directly after being
> connected and do not seem related to the presence/absence of iJack
> strings).
> 
> So my guess is that is a highly device-specific problem and not a
> regression in any part of the kernel.

Yes, it smells more like a firmware bug of the device.

If you prefer having some static names, you can define the entries in
snd_usbmidi_port_info[] in sound/usb/midi.c for each corresponding
MIDI port, too.


Takashi

> 
> 
> On Mon, Oct 14, 2024 at 1:42 AM Takashi Iwai <tiwai@xxxxxxx> wrote:
> >
> > On Mon, 14 Oct 2024 09:36:35 +0200,
> > Takashi Iwai wrote:
> > >
> > > On Sun, 13 Oct 2024 18:56:57 +0200,
> > > Paul Davis wrote:
> > > >
> > > > I don't know where to start with this issue, but since I noticed it
> > > > trying to use a MIDI device, I thought I would start here. Advice on
> > > > where to take it would  be much appreciated.
> > > >
> > > > High Level symptoms:
> > > >
> > > > 1. plugin in a Novation Lanchkey mk4 to (a) a system running kernel
> > > > 6.x (b) a system running kernel 5.x
> > > > 2. run aplaymidi -l or arecordmidi -l
> > > >
> > > >   Results:
> > > >      (a) kernel 6.x: note the presence of two identical MIDI port
> > > > names for the device
> > > >      (b) kernel 5.x: note the presence of two differently named MIDI
> > > > ports for the device
> > > >
> > > > Mid-level diagnosis:
> > > >
> > > > Run lsusb -v on both kernels. For 5.x, note that the iJACK displays
> > > > include a string for the MIDI port name. For 6.x note that this string
> > > > is missing.
> > > >
> > > > Working with devices bearing identical ports for multiple names ranges
> > > > from extremely difficult to impossible.
> > > >
> > > > I have no idea what layer of the stack can be involved here, other
> > > > than that it is not hardware. I've run both 5.x and 6.x kernels on the
> > > > same system.
> > >
> > > Could you try to narrow down the regression range, e.g. by testing
> > > different 5.x and 6.x kernels?  The best would be git-bisect, but
> > > figuring out the first broken kernel version would help a lot
> > > already.
> > >
> > > Also the issue can be very specific to the device, so please give the
> > > details of your device.  e.g. the alsa-info.sh outputs from both cases
> > > as well as lsusb -v outputs.
> >
> > And, if it's about iJack handling for MIDI v1.x, the only recent
> > change I can see is the upstream commit
> > 41c25e193b2befc22462aa41591d397fab174ca1
> >     ALSA: usb-audio: More relaxed check of MIDI jack names
> >
> > You can try to revert it.
> >
> >
> > Takashi