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

[Takashi Iwai <tiwai@xxxxxxx>]

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. 


thanks,

Takashi