AOC 1993 DDC communication failed

[LiAlH4qwq]

the monitor is vga and connected using hdmi to vga adapter

lialh4@lialh4-pc ~> sudo ddcutil getvcp 10 --skip-ddc-checks
VCP (aka MCCS) version for display is undetected or less than 2.0. Interpretation may not be accurate.
VCP code 0x10 (Brightness                    ): Invalid response. status code=ENXIO(-6), Display_Handle[i2c-0: fd=3]

lialh4@lialh4-pc ~> sudo ddcutil detect
Invalid display
   I2C bus:  /dev/i2c-0
   DRM connector:           card0-HDMI-A-1
   EDID synopsis:
      Mfg id:               AOC - UNK
      Model:                1993
      Product code:         6547  (0x1993)
      Serial number:        C993128Z07812
      Binary serial number: 7812 (0x00001e84)
      Manufacture year:     2011,  Week: 28
   DDC communication failed. (getvcp of feature x10 returned Error_Info[ENXIO in ddc_write_read_with_retry, causes: ENXIO])

lialh4@lialh4-pc ~> sudo ddcutil environment
The following tests probe the runtime environment using multiple overlapping methods.
*** Basic System Information ***

ddcutil version: 2.1.2

/proc/version:
   Linux version 6.12.7-200.fc41.x86_64 (mockbuild@8868014edea6461aa4dc1b50f8cdba37) (gcc (GCC) 14.2.1 20240912 (Red Hat 14.2.1-3), GNU ld version 2.43.1-5.fc41) #1 SMP PREEMPT_DYNAMIC Fri Dec 27 17:05:33 UTC 2024

Architecture:     x86_64
Distributor id:   Fedora
Release:          41
Found a known architecture

/proc/cmdline:
   rhgb quiet splash selinux=0 systemd.mount-extra=UUID=118bc764-6e94-45d6-a22a-7b1b8c2cc998:/media/hdd systemd.mount-extra=UUID=EA24525824522839:/media/windows:ntfs3:nofail,force,prealloc,windows_names,uid=1000,gid=1000 systemd.swap-extra=/media/hdd/swapfile:pri=10 resume=UUID=118bc764-6e94-45d6-a22a-7b1b8c2cc998 resume_offset=28853744

*** Primary Check 1: Identify video card and driver ***

Obtaining card and driver information from /sys...
Primary video controller at PCI address 0000:03:00.0 (boot_vga flag is not set)
   Device class:        x030000    VGA compatible controller
   Vendor:              x8086      Intel Corporation
   Device:              x56a5      DG2 [Arc A380]
   Subvendor/Subdevice: 1ef7/1293  Shenzhen Gunnir Technology Development Co., Ltd
   Driver name:         i915
   Driver version:      Unable to determine
   I2C device:          i2c-8      name: i915 gmbus dpd
   I2C device:          i2c-6      name: i915 gmbus dpb
   I2C device:          i2c-9      name: i915 gmbus tc1
   I2C device:          i2c-7      name: i915 gmbus dpc
   I2C device:          i2c-5      name: i915 gmbus dpa
Primary video controller at PCI address 0000:00:02.0 (boot_vga flag is set)
   Device class:        x030000    VGA compatible controller
   Vendor:              x8086      Intel Corporation
   Device:              x3e98      CoffeeLake-S GT2 [UHD Graphics 630]
   Subvendor/Subdevice: 1462/7b23  Micro-Star International Co., Ltd. [MSI]
   Driver name:         i915
   Driver version:      Unable to determine
   I2C device:          i2c-3      name: i915 gmbus dpd
   I2C device:          i2c-1      name: i915 gmbus dpc
   I2C device:          i2c-2      name: i915 gmbus misc
   I2C device:          i2c-0      name: i915 gmbus dpb

*** Primary Check 2: Check that /dev/i2c-* exist and writable ***

Current user: root (0)

Checking /dev/i2c-* devices...

Devices /dev/i2c-* must exist and the logged on user must have read/write permission for those devices (or at least those devices associated 
with monitors).

Typically, this access is enabled by:
  - setting the group for /dev/i2c-* to i2c
  - setting group RW permissions for /dev/i2c-*
  - making the current user a member of group i2c

Alternatively, this can be enabled by just giving everyone RW permission
The following tests probe for these conditions.

Checking for /dev/i2c-* devices...
   crw------- 1 root root 89,  0 Jan 12 21:34 /dev/i2c-0
   crw------- 1 root root 89,  1 Jan 12 21:34 /dev/i2c-1
   crw------- 1 root root 89, 10 Jan 12 21:34 /dev/i2c-10
   crw------- 1 root root 89, 11 Jan 12 21:34 /dev/i2c-11
   crw------- 1 root root 89, 12 Jan 12 21:34 /dev/i2c-12
   crw------- 1 root root 89, 13 Jan 12 21:34 /dev/i2c-13
   crw------- 1 root root 89,  2 Jan 12 21:34 /dev/i2c-2
   crw------- 1 root root 89,  3 Jan 12 21:34 /dev/i2c-3
   crw------- 1 root root 89,  4 Jan 12 21:34 /dev/i2c-4
   crw------- 1 root root 89,  5 Jan 12 21:34 /dev/i2c-5
   crw------- 1 root root 89,  6 Jan 12 21:34 /dev/i2c-6
   crw------- 1 root root 89,  7 Jan 12 21:34 /dev/i2c-7
   crw------- 1 root root 89,  8 Jan 12 21:34 /dev/i2c-8
   crw------- 1 root root 89,  9 Jan 12 21:34 /dev/i2c-9

Current user (root) has RW access to all /dev/i2c-* devices.

*** Primary Check 3: Check that module i2c_dev is loaded ***

Checking for driver i2c_dev...
   sysfs reports module i2c_dev is loaded.
   Module i2c_dev is NOT built into the kernel
   Loadable i2c-dev module found
   Module i2c_dev is loaded

*** Primary Check 4: Driver specific checks ***

Performing driver specific checks...
No driver specific checks apply.

*** Additional probes ***

Examining /sys/bus/i2c/devices...
   /sys/bus/i2c/devices/i2c-0/name:   i915 gmbus dpb
   /sys/bus/i2c/devices/i2c-1/name:   i915 gmbus dpc
   /sys/bus/i2c/devices/i2c-2/name:   i915 gmbus misc
   /sys/bus/i2c/devices/i2c-3/name:   i915 gmbus dpd
   /sys/bus/i2c/devices/i2c-4/name:   AUX D/DDI D/PHY D
   /sys/bus/i2c/devices/i2c-5/name:   i915 gmbus dpa
   /sys/bus/i2c/devices/i2c-6/name:   i915 gmbus dpb
   /sys/bus/i2c/devices/i2c-7/name:   i915 gmbus dpc
   /sys/bus/i2c/devices/i2c-8/name:   i915 gmbus dpd
   /sys/bus/i2c/devices/i2c-9/name:   i915 gmbus tc1
   /sys/bus/i2c/devices/i2c-10/name:  AUX A/DDI A/PHY A
   /sys/bus/i2c/devices/i2c-11/name:  AUX C/DDI C/PHY C
   /sys/bus/i2c/devices/i2c-12/name:  AUX D/DDI D/PHY D
   /sys/bus/i2c/devices/i2c-13/name:  SMBus I801 adapter at efa0
   /sys/bus/i2c/devices/13-0036/name: dummy
   /sys/bus/i2c/devices/13-0037/name: dummy
   /sys/bus/i2c/devices/13-0051/name: ee1004
   /sys/bus/i2c/devices/13-0053/name: ee1004

   Device(s) possibly created by driver ddcci found in /sys/bus/i2c/devices
   May require option --force-slave-address to recover from EBUSY errors.

Env_Accumulator:
   architecture:                  x86_64
   distributor_id                 Fedora
   Drivers detected:              i915
   /dev/i2c device numbers:       0 1 2 3 4 5 6 7 8 9 10 11 12 13
   sysfs_i2c_devices_exist:       true
   /sys/bus/i2c device numbers:   0 1 2 3 4 5 6 7 8 9 10 11 12 13
   dev_i2c_devices_required:      true
   module_i2c_dev_needed:         true
   module_i2c_dev_builtin:        false
   loadable_i2c_dev_exists:       true
   i2c_dev_loaded_or_builtin:     true
   group_i2c_checked:             true
   group_i2c_exists:              false
   dev_i2c_common_group_name:     root
   all_dev_i2c_has_group_i2c:     false
   any_dev_i2c_has_group_i2c:     false
   all_dev_i2c_is_group_rw:       true
   any_dev_i2c_is_group_rw:       false
   cur_uname:                     root
   cur_uid:                       0
   cur_user_in_group_i2c:         false
   cur_user_any_devi2c_rw:        true
   cur_user_all_devi2c_rw:        true

Configuration suggestions:
   Current user has RW access to all /dev/i2c-N devices.
   Skipping further group and permission checks.

[rockowitz]

Likely your HDMI->VGA adapter isn't passing the I²C signals. See the discussion on issue #149.