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