projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| ccf988b6 | 1 | ================================================= |
| c7b25a9e JD |
2 | I2C device driver binding control from user-space |
| 3 | ================================================= | |
| 4 | ||
| 2f07c05f | 5 | Up to kernel 2.6.32, many I2C drivers used helper macros provided by |
| c7b25a9e | 6 | <linux/i2c.h> which created standard module parameters to let the user |
| 2f07c05f | 7 | control how the driver would probe I2C buses and attach to devices. These |
| c7b25a9e JD |
8 | parameters were known as "probe" (to let the driver probe for an extra |
| 9 | address), "force" (to forcibly attach the driver to a given device) and | |
| 10 | "ignore" (to prevent a driver from probing a given address). | |
| 11 | ||
| 2f07c05f | 12 | With the conversion of the I2C subsystem to the standard device driver |
| c7b25a9e JD |
13 | binding model, it became clear that these per-module parameters were no |
| 14 | longer needed, and that a centralized implementation was possible. The new, | |
| 15 | sysfs-based interface is described in the documentation file | |
| 16 | "instantiating-devices", section "Method 4: Instantiate from user-space". | |
| 17 | ||
| 18 | Below is a mapping from the old module parameters to the new interface. | |
| 19 | ||
| 20 | Attaching a driver to an I2C device | |
| 21 | ----------------------------------- | |
| 22 | ||
| ccf988b6 MCC |
23 | Old method (module parameters):: |
| 24 | ||
| 25 | # modprobe <driver> probe=1,0x2d | |
| 26 | # modprobe <driver> force=1,0x2d | |
| 27 | # modprobe <driver> force_<device>=1,0x2d | |
| 28 | ||
| 29 | New method (sysfs interface):: | |
| c7b25a9e | 30 | |
| ccf988b6 | 31 | # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device |
| c7b25a9e JD |
32 | |
| 33 | Preventing a driver from attaching to an I2C device | |
| 34 | --------------------------------------------------- | |
| 35 | ||
| ccf988b6 MCC |
36 | Old method (module parameters):: |
| 37 | ||
| 38 | # modprobe <driver> ignore=1,0x2f | |
| 39 | ||
| 40 | New method (sysfs interface):: | |
| c7b25a9e | 41 | |
| ccf988b6 MCC |
42 | # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device |
| 43 | # modprobe <driver> | |
| c7b25a9e JD |
44 | |
| 45 | Of course, it is important to instantiate the "dummy" device before loading | |
| 46 | the driver. The dummy device will be handled by i2c-core itself, preventing | |
| 47 | other drivers from binding to it later on. If there is a real device at the | |
| 48 | problematic address, and you want another driver to bind to it, then simply | |
| 49 | pass the name of the device in question instead of "dummy". |