'BUG: unable to handle kernel paging request' with Scarlett 6i6 on Ubuntu 14.04 64 bit (kernel 3.13.0-36-generic)

[kaazoo]

I've took the patch https://github.com/smilingthax/alsa-driver_scarlett/blob/patches/s18i8-20140620-kernel.patch , applied it to the 3.13 sources and built all kernel modules.
Then I copied over sound/usb/snd-usb-audio.ko and sound/usb/snd-usbmidi-lib.ko .

When loading the snd-usb-audio module the following kernel error appears:

Sep 24 09:41:34 contentpc33 kernel: [    2.871317] BUG: unable to handle kernel paging request at ffffffffa0b43440
Sep 24 09:41:34 contentpc33 kernel: [    2.872120] IP: [<ffffffff8136f3c2>] memcpy+0x12/0x110
Sep 24 09:41:34 contentpc33 kernel: [    2.872699] PGD 1c11067 PUD 1c12063 PMD 2345c8067 PTE 80000000a1ba3161
Sep 24 09:41:34 contentpc33 kernel: [    2.873484] Oops: 0003 [#1] SMP 
Sep 24 09:41:34 contentpc33 kernel: [    2.873872] Modules linked in: bnep hid_generic rfcomm intel_rapl x86_pkg_temp_thermal bluetooth intel_powerclamp coretemp dcdbas kvm_intel kvm crct10dif_pclmul snd_hda_c
odec_hdmi snd_usb_audio(X+) crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 snd_hda_intel lrw gf128mul snd_hda_codec snd_seq_midi glue_helper ablk_helper snd_usbmidi_lib(X) snd_seq_midi_event cryptd sn
d_hwdep snd_seq snd_rawmidi serio_raw snd_seq_device usbhid hid snd_pcm binfmt_misc sb_edac snd_page_alloc snd_timer edac_core snd fglrx(POX) soundcore amd_iommu_v2 lpc_ich mei_me mei parport_pc mac_hid ppdev 
lp parport psmouse e1000e ahci ptp libahci pps_core megaraid_sas
Sep 24 09:41:34 contentpc33 kernel: [    2.881254] CPU: 0 PID: 395 Comm: systemd-udevd Tainted: P           OX 3.13.0-36-generic #63-Ubuntu
Sep 24 09:41:34 contentpc33 kernel: [    2.882255] Hardware name: Dell Inc. Precision T3600/08HPGT, BIOS A12 11/03/2013
Sep 24 09:41:34 contentpc33 kernel: [    2.883068] task: ffff88023f61e000 ti: ffff8800a2552000 task.ti: ffff8800a2552000
Sep 24 09:41:34 contentpc33 kernel: [    2.883889] RIP: 0010:[<ffffffff8136f3c2>]  [<ffffffff8136f3c2>] memcpy+0x12/0x110
Sep 24 09:41:34 contentpc33 kernel: [    2.884729] RSP: 0018:ffff8800a2553998  EFLAGS: 00010202
Sep 24 09:41:34 contentpc33 kernel: [    2.885309] RAX: ffffffffa0b43440 RBX: ffff88023f1f5000 RCX: 0000000000000004
Sep 24 09:41:34 contentpc33 kernel: [    2.886083] RDX: 0000000000000004 RSI: ffff88023f2b6580 RDI: ffffffffa0b43440
Sep 24 09:41:34 contentpc33 kernel: [    2.886863] RBP: ffff8800a2553a00 R08: 0000000000017180 R09: ffff880247217180
Sep 24 09:41:34 contentpc33 kernel: [    2.887636] R10: ffffea0008fcad80 R11: ffffffff815453c4 R12: 0000000080000300
Sep 24 09:41:34 contentpc33 kernel: [    2.888409] R13: 0000000000000001 R14: 0000000000000021 R15: 0000000000000100
Sep 24 09:41:34 contentpc33 kernel: [    2.889183] FS:  00007f54bd494880(0000) GS:ffff880247200000(0000) knlGS:0000000000000000
Sep 24 09:41:34 contentpc33 kernel: [    2.890059] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Sep 24 09:41:34 contentpc33 kernel: [    2.890681] CR2: ffffffffa0b43440 CR3: 00000000a2520000 CR4: 00000000000407f0
Sep 24 09:41:34 contentpc33 kernel: [    2.891454] Stack:
Sep 24 09:41:34 contentpc33 kernel: [    2.891672]  ffffffffa0b311d2 ffff88023f2b6580 ffff880200000004 ffff880200001388
Sep 24 09:41:34 contentpc33 kernel: [    2.892548]  0000000400000001 0000000000000004 ffff88023f2b6580 0000000400002900
Sep 24 09:41:34 contentpc33 kernel: [    2.893426]  000000000000000a ffff8800a24fd100 0000000000000004 0000000000000001
Sep 24 09:41:34 contentpc33 kernel: [    2.894302] Call Trace:
Sep 24 09:41:34 contentpc33 kernel: [    2.894575]  [<ffffffffa0b311d2>] ? snd_usb_ctl_msg+0xc2/0x160 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.895369]  [<ffffffffa0b3b7aa>] set_ctl_urb2+0xaa/0x100 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.896114]  [<ffffffffa0b3c9fa>] scarlett_mixer_controls+0x28a/0x4c0 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.896966]  [<ffffffffa0b34e8d>] snd_usb_create_mixer+0x19d/0x2f0 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.897790]  [<ffffffffa0b2d403>] ? snd_usb_create_stream+0x1a3/0x200 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.898641]  [<ffffffffa0b2d888>] usb_audio_probe+0x238/0x960 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.899418]  [<ffffffff81549794>] usb_probe_interface+0x1c4/0x2f0
Sep 24 09:41:34 contentpc33 kernel: [    2.900080]  [<ffffffff8149596d>] driver_probe_device+0x12d/0x3e0
Sep 24 09:41:34 contentpc33 kernel: [    2.900741]  [<ffffffff81495cf3>] __driver_attach+0x93/0xa0
Sep 24 09:41:34 contentpc33 kernel: [    2.901345]  [<ffffffff81495c60>] ? __device_attach+0x40/0x40
Sep 24 09:41:34 contentpc33 kernel: [    2.901968]  [<ffffffff814938d3>] bus_for_each_dev+0x63/0xa0
Sep 24 09:41:34 contentpc33 kernel: [    2.902581]  [<ffffffff8149531e>] driver_attach+0x1e/0x20
Sep 24 09:41:34 contentpc33 kernel: [    2.903166]  [<ffffffff81494f00>] bus_add_driver+0x180/0x250
Sep 24 09:41:34 contentpc33 kernel: [    2.903780]  [<ffffffff81496374>] driver_register+0x64/0xf0
Sep 24 09:41:34 contentpc33 kernel: [    2.904385]  [<ffffffff81547f02>] usb_register_driver+0x82/0x160
Sep 24 09:41:34 contentpc33 kernel: [    2.905037]  [<ffffffffa0b57000>] ? 0xffffffffa0b56fff
Sep 24 09:41:34 contentpc33 kernel: [    2.905598]  [<ffffffffa0b5701e>] usb_audio_driver_init+0x1e/0x1000 [snd_usb_audio]
Sep 24 09:41:34 contentpc33 kernel: [    2.906431]  [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
Sep 24 09:41:34 contentpc33 kernel: [    2.907055]  [<ffffffff810598d3>] ? set_memory_nx+0x43/0x50
Sep 24 09:41:34 contentpc33 kernel: [    2.907667]  [<ffffffff810e21ed>] load_module+0x12dd/0x1b40
Sep 24 09:41:34 contentpc33 kernel: [    2.908280]  [<ffffffff810ddc80>] ? store_uevent+0x40/0x40
Sep 24 09:41:34 contentpc33 kernel: [    2.908876]  [<ffffffff810e2bc6>] SyS_finit_module+0x86/0xb0
Sep 24 09:41:34 contentpc33 kernel: [    2.909491]  [<ffffffff8172efad>] system_call_fastpath+0x1a/0x1f
Sep 24 09:41:34 contentpc33 kernel: [    2.910142] Code: 66 0f 1f 84 00 00 00 00 00 e8 fb fb ff ff eb e2 90 90 90 90 90 90 90 90 90 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 f3 48 a5 89 d1 <f3> a4 c3 20 4c 8b 06 4c 8b 4e 08 4c 8b 56 10 4c 8b 5e 18 48 8d 
Sep 24 09:41:34 contentpc33 kernel: [    2.913449] RIP  [<ffffffff8136f3c2>] memcpy+0x12/0x110
Sep 24 09:41:34 contentpc33 kernel: [    2.914036]  RSP <ffff8800a2553998>
Sep 24 09:41:34 contentpc33 kernel: [    2.914414] CR2: ffffffffa0b43440
Sep 24 09:41:34 contentpc33 kernel: [    2.914775] ---[ end trace 88c5ce39f54abc20 ]---

Do you have any hints what could be the problem? Is the patch still up-to-date?

[smilingthax]

Someone sent me a patch a while ago for a similar problem, which I cannot reproduce myself.

In scarlettmixer.c around line 1348:

    /* initialize sampling rate to 48000 */
-   err = set_ctl_urb2(mixer->chip, UAC2_CS_CUR, 0x0100, 0x29, "\x80\xbb\x00\x00", 4);
+   char buffer[4] = { '\x80', '\xbb', '\x00', '\x00' };
+   err = set_ctl_urb2(mixer->chip, UAC2_CS_CUR, 0x0100, 0x29, buffer, 4);
    if (err < 0)
        return err;

[kaazoo]

Thanks for the patch. Now, I can see different channels in alsamixer, but so far the device is not showing up in pulseaudio.

[smilingthax]

As my code only adds mixer support, then everything works as expected, from my perspective.

Audio-playback, etc. is still completely handled by the existing generic usb-audio code in alsa, and playback works even without my mixer-driver (AFAIK there are no known issues for recording/playback with alsa on scarlett devices).
The pulseaudio-problem you're seeing is very probably not rooted in the kernel driver; I guess it's some configuration(?) issue with pulseaudio. jackd is known to work with the device.