Here are some simple methods that should help solve the fatal problem with the videodev not found module.
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@umlaeute thanks. Was able to purchase videodev and v4l2-common which were compiled for a simple kernel and installed v4l2loopback via apt download v4l2loopback-dkms. I am experiencing kernel panic when starting modprobe v4l2loopback:
[25 Apr 06:33] ------------ [cut from this site] ------------[+0.000013] ATTENTION: CPU: 0 PID: At 97640 driver / media / v4l2-core / v4l2-dev.c: 838 __video_register_device + 0xb1b / 0xed0 [videodev][+0.000001] connected modules: v4l2loopback (MA +) v4l2_common (OE) videodev (OE) i2c_mux (OE) v4l2_dv_timings (OE) i2c_core support (EO) UVC MSDOS XFS sch_htb ebt_ip ebtable_filter xt_statistic xt_nat xt_recent ipt_REJECT nf_reject_ipv4 xt_tcpudp nf_conntrack_netlink nfnetlink xt_mark xt_comment Veth ebtable_nat Ebtables ipt_MASQUERADE nf_nat_masquerade_ipv4 xfrm_algo xfrm_user iptable_nat nf_nat_ipv4 xt_addrtype iptable_filter nf_nat br_netfilter bridge STP Ltd. superposition nf_conntrack_ipv4 nf_defrag_ipv4 xt_owner xt_conntrack nf_conntrack iptable_security ip_tables x_tables UDF crc_itu_t serio_raw hv_balloon joydev ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 Btrfs RAID10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx XOR raid6_pq libcrc32c[+0.000042] straightforward raid1 raid0 with multiple paths crc32_pclmul crct10dif_pclmul ghash_clmulni_intel PCBC hid_generic aesni_intel aes_x86_64 crypto_simd glue_helper encrypted pata_acpivhid_hypervkeyboard[+0.000018] CPU: 0 97640 pid: Come: insmod Damaged: G OE 4.13.0-1012-azure # 15-Ubuntu[+0.000001] Hardware name: Microsoft virtual machine / virtual machine, BIOS 090007 06/02/2017[+0 .000001] Task: ffff9478cd15ae80 task.stack: ffffa282c8438000[+0.000005] RIP: 0010: __ video_register_device + 0xb1b / 0xed0 [videodev][+0 .RSP: 000001] 0018: ffffa282c843bc58 FLAGS: 00010246[+0.000001] RAX: ffffffffc07eb500 RBX: ffff94787bc54000 RCX: 000000000000001[+0.000001] RDX: RSI: 00000000ffffffff 0000000000000000 RDI: ffff9478420a5400[+0.000001] RBP: ffffa282c843bc90 Fffffffffc07ed140 r08: R09: ffff9478f9807780[+0.000001] R10: ffffffffc07ead5e R11: R12: ffffffffc080ba80 0000000000000000[+0.000001] R13: 000000000000000 R14: ffff9478420a5400 Ffff94787bc54070[r15: +0.000002] FS: 00007fa8f5807700 (0000) GS: ffff9478f9e00000 (0000) knlGS: 0000000000000000[+0.00001] CS: DS: 0010 0000 ES: 0000 CR0: 0000000080050033[+0.000001] 000000c4213f5500 cr2: CR3: 000000016caac000 CR4: 00000000001406f0[+0.000003] Call tracking:[+0.000006]? init_module + 0x6c9 / 0x1000 [v4l2loopback][+0.000002]? ! ? 0xffffffffc0821000[+0.000005] do_one_initcall + 0x55 / 0x1b0[+0.000005] Klibre + 0x165 / 0x170[? +0.000002]? klibre + 0x165 / 0x170[+0.000002]? ? ? kmem_cache_alloc_trace + 0xfc / 0x1b0[+0.000005] do_init_module + 0x5f / 0x209[+0.000002] Load module + 0x196a / 0x1d70[+0.000005] Ima_post_read_file + 0x7d / 0xa0[? +0.000003] SYSC_finit_module + 0xe5 / 0x120[+0.000001]: sysc_finit_module + 0xe5 / 0x120[+0.000003] SyS_finit_module + 0xe / 0x10[+0.000005] Entry_SYSCALL_64_fastpath + 0x24 / 0xab[+0.000001] RIP: 0033: 0x7fa8f53264d9[+0.000001] 002b: 00007fff50b57aa8 rsp: EFLAGS: 00000202 ORIG_RAX: 00000000000000139[+0.000002] RAX: RBX: ffffffffffffffda 00000000000000003 RCX: 00007fa8f53264d9[+0.000001] 0000000000000000 rdx: RSI: 0000560da9fa026b RDI: 000000000000003[+0.000001] RBP: R08: 00007fff50b56a60 0000000000000000 R09: 00007fa8f55ebea0[+ 0.R10: 000000] 000000000000003 R11: 000000000000202 R12: 00000000000000098[+ 0.R13: 000001] 0000560dab2341d0 R14: 0000560dab234130 R15: 00007fff50b5692c[+0.000002] Code: b3 10 48 c7 c7 c0 30 81 c0 e8 e2 30 e5 d0 41 c7 87 40 next month 00 00 ff ff ff ff seventy two 83 c4 18 44 89 e0 5b forty one 5c 41 5d 41 5th forty-one 5d 5f c3 <0f> ff b8 consultant ff ff ff c3 0f ff b8 buys Angry Birds Verlag ff ff ff c3 eighty five c9 0f 84 99[+0.000026] End --- [Trace ceadd6e2eeec302e] ---[+ 0.V4l2loopback: 000001] failed video_register_device ()[+0.019533] kernfs: unable to delete format, no directory[+0.000006] ------------ [lower] ------------
The warning here refers to the fact that driver / media / v4l2-core / v4l2-dev.c: 838 will refer to evaluations in my kernel that the version callback is considered mouthnew:
https://elixir.bootlin.com/linux/latest/source/drivers/media/v4l2-core/v4l2-dev.c#L840
v4l2_loopback_init returns successfully:
https://github.com/umlaeute/v4l2loopback/blob/master/v4l2loopback.c#L2416
and the video_register_device tries to call:
https://github.com/umlaeute/v4l2loopback/blob/master/v4l2loopback.c#L2422
Do you have any idea why the version callback should be set to zero at all?
@umlaeute thanks. Was able to combine videodev and v4l2-common for my kernel and install v4l2loopback on apt v4l2loopback-dkms install. I am experiencing kernel panic when starting modprobe v4l2loopback:
Note applies to driver / media / v4l2-core / v4l2-dev.c: 838 on several other kernels refers to checking if the Let it go callback is installed:
https://elixir.bootlin.com/linux/latest/source/drivers/media/v4l2-core/v4l2-dev.c#L840
v4l2_loopback_init returns successfully:
https://github.com/umlaeute/v4l2loopback/blob/master/v4l2loopback.c#L2416
and most of the video_register_device is called:
https://github.com/umlaeute/v4l2loopback/blob/master/v4l2loopback.c#L2422
So, do you have any ideas why the reminder should be set to zero?
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[April 25, 06:33] ------------ [cut here] ------------[+0.000013] ATTENTION: CPU: 0 PID: At 97640 driver / media / v4l2-core / v4l2-dev.c: 838 __video_register_device + 0xb1b / 0xed0[videodev][+0.000001] Such modules: v4l2loopback (MA +) v4l2_common (OE) videodev (OE) i2c_mux (OE) v4l2_dv_timings (OE) i2c_core support (EO) UVC MSDOS XFS sch_htb ebt_ip ebtable_filter xt_statistic xt_nat xt_recent ipt_REJECT nf_reject_ipv4 xt_tcpudp nf_conntrack_netlink nfnetlink xt_mark xt_comment Veth ebtable_nat ebtables ipt_MASQUERADE nf_na
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