Re: Scarlett 16i16 4th Gen: I/O error on kernel 6.19-rc6 (works on 6.18)

[Takashi Iwai <tiwai@suse.de>]

On Sat, 24 Jan 2026 17:24:07 +0100,
Geoffrey D. Bennett wrote:
> 
> Hi Ruslan,
> 
> Audio playback for Focusrite USB interfaces is handled by the generic
> USB audio driver (snd-usb-audio); the FCP driver I maintain only
> handles the control protocol (mixer, routing, etc.) over a separate
> USB endpoint — it's not involved in the actual audio data transfer.
> 
> I've CC'd the ALSA maintainers and linux-sound list to continue the
> discussion there.
> 
> Regards,
> Geoffrey.
> 
> On Sat, Jan 24, 2026 at 08:56:38PM +0500, Ruslan Garynin wrote:
> >    Hi Geoffrey,
> > 
> >    I found a regression affecting Scarlett 16i16 4th Gen playback on kernel
> >    6.19-rc6.
> > 
> >    Summary:
> >    - Working: 6.18.6-zen1-1-zen
> >    - Broken: 6.19.0-rc6-1-mainline
> >    - Issue: I/O error on USB audio playback
> >    - HDA/HDMI audio works fine on 6.19-rc6, so it's USB audio specific
> > 
> >    Test:
> >      systemctl --user stop pipewire pipewire-pulse wireplumber
> >      speaker-test -D hw:3 -c 18 -t sine -F S32_LE
> > 
> >    On 6.18 (works):
> >      0 - Front Left
> >      1 - Front Right
> >      ...
> >      15 - Channel 16
> >      (sound plays)
> > 
> >    On 6.19-rc6 (fails):
> >      0 - Front Left
> >      Write error: -5,Input/output error
> > 
> >    Device info:
> >      USB ID: 1235:821b
> >      FCP driver loads OK: "Focusrite Control Protocol Driver ready"
> >      Implicit Feedback Mode: Yes
> >      No errors in dmesg
> > 
> >    /proc/asound/card3/stream0:
> >      Format: S32_LE
> >      Channels: 18
> >      Endpoint: 0x01 (1 OUT) (ASYNC)
> >      Rates: 44100, 48000
> >      Sync Endpoint: 0x81 (1 IN)
> >      Implicit Feedback Mode: Yes
> > 
> >    Note: This might get fixed on its own when mainline is updated further
> >    before
> >    the stable 6.19 release. I'm just reporting this in case it doesn't, so
> >    you're
> >    aware of a potential issue that could affect users when 6.19 changes
> >    eventually
> >    land in stable kernels.
> > 
> >    Let me know if you need any additional info or testing.
> > 
> >    Thanks for maintaining the Scarlett driver!
> > 
> >    Best regards,
> >    Ruslan Garynin

Could you check whether the earlier 6.19-rc shows the same problem?
Also check the very latest Linus tree, too.


Takashi