0001 ================================================================
0002 I2C device driver binding control from user-space in old kernels
0003 ================================================================
0004
0005 .. NOTE::
0006 Note: this section is only relevant if you are handling some old code
0007 found in kernel 2.6. If you work with more recent kernels, you can
0008 safely skip this section.
0009
0010 Up to kernel 2.6.32, many I2C drivers used helper macros provided by
0011 <linux/i2c.h> which created standard module parameters to let the user
0012 control how the driver would probe I2C buses and attach to devices. These
0013 parameters were known as ``probe`` (to let the driver probe for an extra
0014 address), ``force`` (to forcibly attach the driver to a given device) and
0015 ``ignore`` (to prevent a driver from probing a given address).
0016
0017 With the conversion of the I2C subsystem to the standard device driver
0018 binding model, it became clear that these per-module parameters were no
0019 longer needed, and that a centralized implementation was possible. The new,
0020 sysfs-based interface is described in
0021 Documentation/i2c/instantiating-devices.rst, section
0022 "Method 4: Instantiate from user-space".
0023
0024 Below is a mapping from the old module parameters to the new interface.
0025
0026 Attaching a driver to an I2C device
0027 -----------------------------------
0028
0029 Old method (module parameters)::
0030
0031 # modprobe <driver> probe=1,0x2d
0032 # modprobe <driver> force=1,0x2d
0033 # modprobe <driver> force_<device>=1,0x2d
0034
0035 New method (sysfs interface)::
0036
0037 # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
0038
0039 Preventing a driver from attaching to an I2C device
0040 ---------------------------------------------------
0041
0042 Old method (module parameters)::
0043
0044 # modprobe <driver> ignore=1,0x2f
0045
0046 New method (sysfs interface)::
0047
0048 # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
0049 # modprobe <driver>
0050
0051 Of course, it is important to instantiate the ``dummy`` device before loading
0052 the driver. The dummy device will be handled by i2c-core itself, preventing
0053 other drivers from binding to it later on. If there is a real device at the
0054 problematic address, and you want another driver to bind to it, then simply
0055 pass the name of the device in question instead of ``dummy``.
