Hi,

I have recently upgraded to a newer kernel-version (from 2.6.12.r6 to 2.6.13-gentoo-r5) and just realized the USB MIDI interface, which was working before, isn't recognized anymore.
Looking up dmesg spits this out:

Unable to handle kernel NULL pointer dereference at virtual address 00000018
 printing eip:
c03e83cd
*pde = 00000000
Oops: 0002 [#1]
PREEMPT SMP
Modules linked in: snd_pcm_oss snd_mixer_oss snd_seq_dummy snd_seq_oss snd_seq_mid
vent snd_seq snd_usb_audio snd_usb_lib snd_rawmidi snd_seq_device snd_hwdep snd_in
8x0 snd_ac97_codec snd_pcm snd_timer snd snd_page_alloc usbhid psmouse evdev nvidi
ealtime usb_midi audio adi gameport
CPU:    0
EIP:    0060:[<c03e83cd>]    Tainted: P      VLI
EFLAGS: 00010046   (2.6.13-gentoo-r5)
EIP is at _spin_lock_irqsave+0x1d/0x90
eax: 00000000   ebx: 00000018   ecx: 00000001   edx: 00000202
esi: dfce8000   edi: 00000001   ebp: dfce9e10   esp: dfce9ddc
ds: 007b   es: 007b   ss: 0068
Process khubd (pid: 117, threadinfo=dfce8000 task=c1577530)
Stack: 00000018 00000000 c011b54e d9ca4b18 00000003 00000001 00000000 00000000
       00000202 00000003 dfdd6800 dfdb0780 dfdb078c d987b920 e092ca8b 00000000
       df24f200 e092f620 e092f640 c0327a46 df24f200 df24f200 df24f214 df24f294
Call Trace:
 [<c011b54e>] __wake_up+0x1e/0x60
 [<e092ca8b>] usb_midi_disconnect+0xab/0xf8 [usb_midi]
 [<c0327a46>] usb_unbind_interface+0x86/0x90
 [<c02bf93f>] __device_release_driver+0x8f/0xb0
 [<c02bf980>] device_release_driver+0x20/0x40
 [<c02bf089>] bus_remove_device+0x79/0x90
 [<c02be082>] device_del+0x32/0x90
 [<c0331aca>] usb_disable_device+0x16a/0x1a0
 [<c032a806>] usb_disconnect+0xa6/0x190
 [<c032cd07>] hub_port_connect_change+0x4c7/0x500
 [<c032d226>] hub_events+0x4e6/0x620
 [<c032d385>] hub_thread+0x25/0x130
 [<c0135970>] autoremove_wake_function+0x0/0x60
 [<c0135970>] autoremove_wake_function+0x0/0x60
 [<c032d360>] hub_thread+0x0/0x130
 [<c01354ba>] kthread+0xba/0xc0
 [<c0135400>] kthread+0x0/0xc0
 [<c0101215>] kernel_thread_helper+0x5/0x10
Code: e8 59 ef ff ff eb c3 8d b4 26 00 00 00 00 83 ec 08 89 1c 24 89 c3 b8 00 e0 f
f 89 74 24 04 21 e0 ff 40 14 89 c6 9c 5a fa 31 c0 <86> 03 84 c0 7e 14 c7 43 04 00
00 00 8b 74 24 04 89 d0 8b 1c
 <6>note: khubd[117] exited with preempt_count 1
uhci_hcd 0000:00:1d.1: suspend_rh (auto-stop)

This was what appeared most strange to me. I've checked /etc/hotplug/blacklist and it seems all right(a usb-midi entry) and /etc/modules.autoload/kernel-2.6 for both, snd-usb-audio and usb-midi entries.
After restarting alsasound it shows me that it sets two sound card devices (one for built-in audio and snd-usb-audio).

This is the content of /etc/modules.d/alsa:

alias snd-card-0 snd-intel8x0
alias sound-slot-0 snd-intel8x0
alias snd-card-1 snd-usb-audio
alias sound-slot-1 snd-usb-audio

Another double check on the kernel config revealed that all was in its place, i.e. building snd-usb-audio as a module etc.
What could this be??

Karsten

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