On Sunday, 19 January 2020 15:02:36 GMT edes wrote:
> el 2020-01-18 a las 12:58 edes escribió:
> > But now for some reason it works as playback device, but is not
> > recognized as capture device.
>
> I kept investigating, and all the evidence points to a kernel problem
> (gentoo-sources).
>
> I tried several versions, everything works fine with kernels up to 5.4.10,
> problems appear with 5.4.11, 12 and 13. Same results on two different
> machines with two different cards (same model).
>
> It seems that some changes were introduced in 5.4.11 that affect USB
> audio. This only affects my Sound Devices USPre2 cards, I tried with a
> cheap card, and it continues to work normally with all kernels.
>
> Where should I report this problem and who could help?
>
> Thanks.
>
>
> --
You could compare the dmesg output of working and non-working kernels and see
what differences are present, then google for bugs/solutions on that basis.
You could also diff the two different kernel tree versions and see what
drivers have changed. Also, check the kernel git repo to see what the
changelog reports, which could narrow down the diff'ed files:
https://github.com/torvalds/linux
You could post a bug in BGO, but the devs may ask you to enable/undertake
kernel debugging, which is not a 5 minute job and/or use vanilla kernel
sources and report it upstream, depending on how rare this problem is and if
they have been bitten by the same bug themselves.
https://wiki.gentoo.org/wiki/Kernel_Crash_Dumps
https://www.oreilly.com/library/view/linux-device-drivers/0596005903/ch04.html
--
Regards,
Mick
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