[Bug 1900122] Re: Unsupported ioctl: cmd=0xffffffff80685600 when accessing /dev/video* in aarch64 guest

[Peter Maydell]

** Tags removed: aarch64
** Tags added: arm

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Title:
  Unsupported ioctl: cmd=0xffffffff80685600 when accessing /dev/video*
  in aarch64 guest

Status in QEMU:
  New

Bug description:
  **Description:**
  Any attempt to work with video in aarch64 architecture emulated on x86_64 
leads currently to the error "Function not implemented". For example:

  ```
  # v4l2-ctl -l --verbose
  Failed to open /dev/video0: Function not implemented

  root@12dd9b6fcfcb:/# ll /dev/video*
  crw-rw---- 1 root video 81, 0 Oct 16 09:23 /dev/video0
  crw-rw---- 1 root video 81, 1 Oct 16 09:23 /dev/video1

  ```

  **Steps to reproduce the issue:**

  I have a following setup:

  Host Hardware: x86_64 equipped with a webcam (tried different webcams)
  Host OS: Ubuntu 20.04.1

  Guest Architecture: aarch64
  Guest OS: Ubuntu 20.04 (also tried 16.x and 18.x)

  Emulation: quemu-user-static (also tried binfmt)

  Guest OS is running via Docker + QEMU

  ```
  ➜ cat /proc/sys/fs/binfmt_misc/qemu-aarch64
  enabled
  interpreter /usr/bin/qemu-aarch64-static
  flags: F
  offset 0
  magic 7f454c460201010000000000000000000200b700
  mask ffffffffffffff00fffffffffffffffffeffffff
  ```

  **Results received:**
  see desrciption.

  
  **Environment:**

  * QEMU version: (if you can know it):

  ipxe-qemu-256k-compat-efi-roms/focal,now 1.0.0+git-20150424.a25a16d-0ubuntu4 
all [installed,automatic]
  ipxe-qemu/focal-updates,now 1.0.0+git-20190109.133f4c4-0ubuntu3.2 all 
[installed,automatic]
  qemu-block-extra/focal-updates,now 1:4.2-3ubuntu6.7 amd64 
[installed,automatic]
  qemu-kvm/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed]
  qemu-system-common/focal-updates,now 1:4.2-3ubuntu6.7 amd64 
[installed,automatic]
  qemu-system-data/focal-updates,now 1:4.2-3ubuntu6.7 all [installed,automatic]
  qemu-system-gui/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed,automatic]
  qemu-system-x86/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed,automatic]
  qemu-user-binfmt/focal-updates,now 1:4.2-3ubuntu6.7 amd64 
[installed,automatic]
  qemu-user/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed]
  qemu-utils/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed,automatic]
  qemu/focal-updates,now 1:4.2-3ubuntu6.7 amd64 [installed]

  * Container application: Docker

  **Output of `docker version`, `podman version` or `singularity
  version`**

  ```
  ➜ docker version
  Client: Docker Engine - Community
   Version:           20.10.0-beta1
   API version:       1.40
   Go version:        go1.13.15
   Git commit:        ac365d7
   Built:             Tue Oct 13 18:15:22 2020
   OS/Arch:           linux/amd64
   Context:           default
   Experimental:      true

  Server: Docker Engine - Community
   Engine:
    Version:          19.03.13
    API version:      1.40 (minimum version 1.12)
    Go version:       go1.13.15
    Git commit:       4484c46d9d
    Built:            Wed Sep 16 17:01:20 2020
    OS/Arch:          linux/amd64
    Experimental:     false
   containerd:
    Version:          1.4.1
    GitCommit:        c623d1b36f09f8ef6536a057bd658b3aa8632828
   runc:
    Version:          1.0.0-rc92
    GitCommit:        ff819c7e9184c13b7c2607fe6c30ae19403a7aff
   docker-init:
    Version:          0.18.0
    GitCommit:        fec3683

  ```

  Guest aarch64 runs in privileged mode:

  `docker run --privileged --device=/dev/video0:/dev/video0 --env
  DISPLAY=unix$DISPLAY -v $XAUTH:/root/.Xauthority  -v
  /tmp/.X11-unix:/tmp/.X11-unix -it --rm arm64v8/ubuntu:20.04 bash`

  **Additional information:**
  I tried also binfmt way to register emulators. The output of `v4l-ctl` was a 
little bit different:

  ```
  # v4l2-ctl -l
  Unsupported ioctl: cmd=0xffffffff80685600
  Failed to open /dev/video0: Function not implemented

  ```

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