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[Paolo Pisati <1417032@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

My board has an i2c bus (and devices attached to it), but the
corresponding /dev entries are missing and userspace can't access these
devices until the i2c-dev module is loaded:

[flag@luxor ~]$ ls -la /sys/bus/i2c/devices/
total 0
drwxr-xr-x 2 root root 0 Feb  2 08:38 .
drwxr-xr-x 4 root root 0 Feb  2 08:38 ..
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-0 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-0
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-1 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-1
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-2 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-2
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-3 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-3
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-4 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-4
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-5 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-5
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-6 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-6
lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-7 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-7
[flag@luxor ~]$ i2cdetect -l
[flag@luxor ~]$ ls -la /dev/i2c*
ls: cannot access /dev/i2c*: No such file or directory
[flag@luxor ~]$


[flag@luxor ~]$ sudo modprobe i2c-dev                                                                                                       
[flag@luxor ~]$ ls -la /dev/i2c*
crw-rw---- 1 root i2c 89, 0 Feb  2 09:33 /dev/i2c-0
crw-rw---- 1 root i2c 89, 1 Feb  2 09:33 /dev/i2c-1
crw-rw---- 1 root i2c 89, 2 Feb  2 09:33 /dev/i2c-2
crw-rw---- 1 root i2c 89, 3 Feb  2 09:33 /dev/i2c-3
crw-rw---- 1 root i2c 89, 4 Feb  2 09:33 /dev/i2c-4
crw-rw---- 1 root i2c 89, 5 Feb  2 09:33 /dev/i2c-5
crw-rw---- 1 root i2c 89, 6 Feb  2 09:33 /dev/i2c-6
crw-rw---- 1 root i2c 89, 7 Feb  2 09:33 /dev/i2c-7
[flag@luxor ~]$ i2cdetect -l
i2c-0   unknown         Radeon i2c bit bus 0x90                 N/A
i2c-1   unknown         Radeon i2c bit bus 0x91                 N/A
i2c-2   unknown         Radeon i2c bit bus 0x92                 N/A
i2c-3   unknown         Radeon i2c bit bus 0x93                 N/A
i2c-4   unknown         Radeon i2c bit bus 0x94                 N/A
i2c-5   unknown         Radeon i2c bit bus 0x95                 N/A
i2c-6   unknown         Radeon i2c bit bus 0x96                 N/A
i2c-7   unknown         Radeon i2c bit bus 0x97                 N/A
[flag@luxor ~]$

Since the module is not automatically loaded, and there's no clue to
load it if i2c devices fail to work (and people might think it's a bug),
i propose to build it statically (it adds ~8k to the uncompressed kernel
image).

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1417032

Title:
  Userspace can't access i2c devices (missing i2c entries in /dev)

Status in linux package in Ubuntu:
  New

Bug description:
  My board has an i2c bus (and devices attached to it), but the
  corresponding /dev entries are missing and userspace can't access
  these devices until the i2c-dev module is loaded:

  [flag@luxor ~]$ ls -la /sys/bus/i2c/devices/
  total 0
  drwxr-xr-x 2 root root 0 Feb  2 08:38 .
  drwxr-xr-x 4 root root 0 Feb  2 08:38 ..
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-0 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-0
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-1 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-1
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-2 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-2
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-3 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-3
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-4 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-4
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-5 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-5
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-6 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-6
  lrwxrwxrwx 1 root root 0 Feb  2 09:28 i2c-7 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-7
  [flag@luxor ~]$ i2cdetect -l
  [flag@luxor ~]$ ls -la /dev/i2c*
  ls: cannot access /dev/i2c*: No such file or directory
  [flag@luxor ~]$

  
  [flag@luxor ~]$ sudo modprobe i2c-dev                                                                                                       
  [flag@luxor ~]$ ls -la /dev/i2c*
  crw-rw---- 1 root i2c 89, 0 Feb  2 09:33 /dev/i2c-0
  crw-rw---- 1 root i2c 89, 1 Feb  2 09:33 /dev/i2c-1
  crw-rw---- 1 root i2c 89, 2 Feb  2 09:33 /dev/i2c-2
  crw-rw---- 1 root i2c 89, 3 Feb  2 09:33 /dev/i2c-3
  crw-rw---- 1 root i2c 89, 4 Feb  2 09:33 /dev/i2c-4
  crw-rw---- 1 root i2c 89, 5 Feb  2 09:33 /dev/i2c-5
  crw-rw---- 1 root i2c 89, 6 Feb  2 09:33 /dev/i2c-6
  crw-rw---- 1 root i2c 89, 7 Feb  2 09:33 /dev/i2c-7
  [flag@luxor ~]$ i2cdetect -l
  i2c-0   unknown         Radeon i2c bit bus 0x90                 N/A
  i2c-1   unknown         Radeon i2c bit bus 0x91                 N/A
  i2c-2   unknown         Radeon i2c bit bus 0x92                 N/A
  i2c-3   unknown         Radeon i2c bit bus 0x93                 N/A
  i2c-4   unknown         Radeon i2c bit bus 0x94                 N/A
  i2c-5   unknown         Radeon i2c bit bus 0x95                 N/A
  i2c-6   unknown         Radeon i2c bit bus 0x96                 N/A
  i2c-7   unknown         Radeon i2c bit bus 0x97                 N/A
  [flag@luxor ~]$

  Since the module is not automatically loaded, and there's no clue to
  load it if i2c devices fail to work (and people might think it's a
  bug), i propose to build it statically (it adds ~8k to the
  uncompressed kernel image).

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