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 21Documentation/i2c/instantiating-devices.rst, section 22"Method 4: Instantiate from user-space". 23 24Below is a mapping from the old module parameters to the new interface. 25 26Attaching a driver to an I2C device 27----------------------------------- 28 29Old method (module parameters):: 30 31 # modprobe <driver> probe=1,0x2d 32 # modprobe <driver> force=1,0x2d 33 # modprobe <driver> force_<device>=1,0x2d 34 35New method (sysfs interface):: 36 37 # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device 38 39Preventing a driver from attaching to an I2C device 40--------------------------------------------------- 41 42Old method (module parameters):: 43 44 # modprobe <driver> ignore=1,0x2f 45 46New method (sysfs interface):: 47 48 # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device 49 # modprobe <driver> 50 51Of course, it is important to instantiate the ``dummy`` device before loading 52the driver. The dummy device will be handled by i2c-core itself, preventing 53other drivers from binding to it later on. If there is a real device at the 54problematic address, and you want another driver to bind to it, then simply 55pass the name of the device in question instead of ``dummy``. 56