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