1================================================================
2I2C device driver binding control from user-space in old kernels
3================================================================
4
5.. NOTE::
6   Note: this section is only relevant if you are handling some old code
7   found in kernel 2.6. If you work with more recent kernels, you can
8   safely skip this section.
9
10Up to kernel 2.6.32, many I2C drivers used helper macros provided by
11<linux/i2c.h> which created standard module parameters to let the user
12control how the driver would probe I2C buses and attach to devices. These
13parameters were known as ``probe`` (to let the driver probe for an extra
14address), ``force`` (to forcibly attach the driver to a given device) and
15``ignore`` (to prevent a driver from probing a given address).
16
17With the conversion of the I2C subsystem to the standard device driver
18binding model, it became clear that these per-module parameters were no
19longer needed, and that a centralized implementation was possible. The new,
20sysfs-based interface is described in :doc:`instantiating-devices`, section
21"Method 4: Instantiate from user-space".
22
23Below is a mapping from the old module parameters to the new interface.
24
25Attaching a driver to an I2C device
26-----------------------------------
27
28Old method (module parameters)::
29
30  # modprobe <driver> probe=1,0x2d
31  # modprobe <driver> force=1,0x2d
32  # modprobe <driver> force_<device>=1,0x2d
33
34New method (sysfs interface)::
35
36  # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
37
38Preventing a driver from attaching to an I2C device
39---------------------------------------------------
40
41Old method (module parameters)::
42
43  # modprobe <driver> ignore=1,0x2f
44
45New method (sysfs interface)::
46
47  # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
48  # modprobe <driver>
49
50Of course, it is important to instantiate the ``dummy`` device before loading
51the driver. The dummy device will be handled by i2c-core itself, preventing
52other drivers from binding to it later on. If there is a real device at the
53problematic address, and you want another driver to bind to it, then simply
54pass the name of the device in question instead of ``dummy``.
55