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- ================================================================
- I2C device driver binding control from user-space in old kernels
- ================================================================
- .. NOTE::
- Note: this section is only relevant if you are handling some old code
- found in kernel 2.6. If you work with more recent kernels, you can
- safely skip this section.
- Up to kernel 2.6.32, many I2C drivers used helper macros provided by
- <linux/i2c.h> which created standard module parameters to let the user
- control how the driver would probe I2C buses and attach to devices. These
- parameters were known as ``probe`` (to let the driver probe for an extra
- address), ``force`` (to forcibly attach the driver to a given device) and
- ``ignore`` (to prevent a driver from probing a given address).
- With the conversion of the I2C subsystem to the standard device driver
- binding model, it became clear that these per-module parameters were no
- longer needed, and that a centralized implementation was possible. The new,
- sysfs-based interface is described in
- Documentation/i2c/instantiating-devices.rst, section
- "Method 4: Instantiate from user-space".
- Below is a mapping from the old module parameters to the new interface.
- Attaching a driver to an I2C device
- -----------------------------------
- Old method (module parameters)::
- # modprobe <driver> probe=1,0x2d
- # modprobe <driver> force=1,0x2d
- # modprobe <driver> force_<device>=1,0x2d
- New method (sysfs interface)::
- # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
- Preventing a driver from attaching to an I2C device
- ---------------------------------------------------
- Old method (module parameters)::
- # modprobe <driver> ignore=1,0x2f
- New method (sysfs interface)::
- # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
- # modprobe <driver>
- Of course, it is important to instantiate the ``dummy`` device before loading
- the driver. The dummy device will be handled by i2c-core itself, preventing
- other drivers from binding to it later on. If there is a real device at the
- problematic address, and you want another driver to bind to it, then simply
- pass the name of the device in question instead of ``dummy``.
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