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1 | ================================================================ |
2 | I2C device driver binding control from user-space in old kernels | |
3 | ================================================================ | |
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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 | ||
2f07c05f | 10 | Up to kernel 2.6.32, many I2C drivers used helper macros provided by |
c7b25a9e | 11 | <linux/i2c.h> which created standard module parameters to let the user |
2f07c05f | 12 | control how the driver would probe I2C buses and attach to devices. These |
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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). | |
c7b25a9e | 16 | |
2f07c05f | 17 | With the conversion of the I2C subsystem to the standard device driver |
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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, | |
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20 | sysfs-based interface is described in :doc:`instantiating-devices`, section |
21 | "Method 4: Instantiate from user-space". | |
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22 | |
23 | Below is a mapping from the old module parameters to the new interface. | |
24 | ||
25 | Attaching a driver to an I2C device | |
26 | ----------------------------------- | |
27 | ||
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28 | Old method (module parameters):: |
29 | ||
30 | # modprobe <driver> probe=1,0x2d | |
31 | # modprobe <driver> force=1,0x2d | |
32 | # modprobe <driver> force_<device>=1,0x2d | |
33 | ||
34 | New method (sysfs interface):: | |
c7b25a9e | 35 | |
ccf988b6 | 36 | # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device |
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37 | |
38 | Preventing a driver from attaching to an I2C device | |
39 | --------------------------------------------------- | |
40 | ||
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41 | Old method (module parameters):: |
42 | ||
43 | # modprobe <driver> ignore=1,0x2f | |
44 | ||
45 | New method (sysfs interface):: | |
c7b25a9e | 46 | |
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47 | # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device |
48 | # modprobe <driver> | |
c7b25a9e | 49 | |
1ef05722 | 50 | Of course, it is important to instantiate the ``dummy`` device before loading |
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51 | the driver. The dummy device will be handled by i2c-core itself, preventing |
52 | other drivers from binding to it later on. If there is a real device at the | |
53 | problematic address, and you want another driver to bind to it, then simply | |
1ef05722 | 54 | pass the name of the device in question instead of ``dummy``. |